Sparks v Hobson; Gray v Hobson [2018] NSWCA 29

Court of Appeal Supreme Court New South Wales Medium Neutral Citation: Sparks v Hobson; Gray v Hobson [2018] NSWCA 29 Hearing dates: 6 and 7 November 2017 Decision date: 01 March 2018 Before: Basten JA at [1]; Macfarlan JA at [107]; Simpson JA at [239] Decision: (1) Dismiss Dr Sparks' appeal with costs; (2) Allow Dr Gray's appeal; (3) Set aside orders 1 and 2 made at first instance so far as they relate to Dr Gray; (4) Judgment for Dr Gray on the respondent's claim against him. (5) Order the respondent to pay Dr Gray's costs of the proceedings at first instance and on appeal; (6) Grant the respondent a certificate under the Suitors' Fund Act 1951 (NSW) in relation to Dr Gray's appeal. Catchwords: NEGLIGENCE – medical negligence – respondent became paraplegic as a result of surgery – principal anaesthetist's attempts to address respondent's continuing high carbon dioxide levels during operation were unsuccessful – whether head surgeon and principal anaesthetist negligent in failing to terminate operation earlier than occurred – roles and responsibilities of head surgeon and principal anaesthetist

NEGLIGENCE – medical negligence – peer professional opinion – Civil Liability Act 2002 (NSW) s 5O – whether necessary that at the time of the alleged negligence there was an established practice which was widely accepted as competent medical practice – McKenna v Hunter & New England Local Health District [2013] NSWCA 476; (2013) Aust Torts Rep 82-158 considered

NEGLIGENCE – medical negligence – inherent risk – Civil Liability Act 2002 (NSW) s 5I – whether risk of neurological injury was inherent risk of surgery that could not have been avoided by the exercise of reasonable care and skill Legislation Cited: Civil Liability Act 2002 (NSW), ss 5B, 5 I, 5 O; Pt 1A, Div 6 Interpretation Act 1987 (NSW), ss 34, 35 Cases Cited: Adeels Palace Pty Ltd v Moubarak; Adeels Palace Pty Ltd v Bou Najem (2009) 239 CLR 420; [2009] HCA 48 Bolam v Friern Hospital Management Committee [1957] 1 WLR 582; [1957] 2 All ER 118 CEMEX Australia Pty Ltd v Takeovers Panel (2009) 177 FCR 98; [2009] FCAFC 78 Dobler v Halverson (2007) 70 NSWLR 151; [2007] NSWCA 335 Elliott v Bickerstaff (1999) 48 NSWLR 214; [1999] NSWCA 453 Federal Commissioner of Taxation v St Helens Farm (ACT) Pty Ltd (1981) 146 CLR 336 at 410; [1981] HCA 4 Garcia v National Australia Bank (1998) 194 CLR 395; [1998] HCA 48 Holmes a Court v Papaconstuntinos [2011] NSWCA 59 Gett v Tabet (2009) 254 ALR 504; [2009] NSWCA 76 Harrison v Melhem (2008) 72 NSWLR 380; [2008] NSWCA 67 Hunter and New England Local Health District v McKenna; Hunter and New England Local Health District v Simon (2014) 253 CLR 270; [2014] HCA 44 McKenna v Hunter & New England Local Health District; Simon v Hunter & New England Local Health District [2013] NSWCA 476; (2013) Aust Torts Reports 82-158 Ingram v Fitzgerald [1936] NZLR 905 Montgomery v Lanarkshire Health Board [2015] 1 AC 1430 Naxakis v Western General Hospital (1999) 197 CLR 269; [1999] HCA 22 Paul v Cooke (2013) 85 NSWLR 167; [2013] NSWCA 311 Qidwai v Brown [1984] 1 NSWLR 100 Rogers v Whitaker (1992) 175 CLR 479; [1992] HCA 58 Rosenberg v Percival (2001) 205 CLR 434; [2001] HCA 18 Sidaway v Board of Governors of the Bethlem Royal Hospital [1984] 1 QB 493 Sidaway v Board of Governors of Bethlem Royal Hospital [1985] AC 871 Sydney South West Area Health Service v MD [2009] NSWCA 343; (2009) 260 ALR 702 The Nominal Defendant v Buck Cooper [2017] NSWCA 280 Category: Principal judgment Parties: CA 2017/165207 Dr Christopher Sparks (Appellant) Brendan Hobson (Respondent)

CA 2017/168320 Dr Randolph Gray (Appellant) Brendan Hobson (Respondent) Representation: Counsel: CA 2017/165207 R Cheney SC / K Burke (Appellant) P Menzies QC / R de Meyrick (Respondent)

CA 2017/168320 M Windsor SC / S Woods (Appellant) P Menzies QC / R de Meyrick (Respondent)

Solicitors: CA 2017/165207 Avant Law (Appellant) Grieve Watson Kelly (Respondent)

CA 2017/168320 Norton Rose Fulbright Australia (Appellant) Grieve Watson Kelly (Respondent) File Number(s): CA 2017/165207; 2017/168320 Decision under appeal Court or tribunal: Supreme Court Jurisdiction: Common Law Citation: [2017] NSWSC 589 Date of Decision: 17 May 2017 Before: Harrison J File Number(s): SC 2013/80267

[Note: The Uniform Civil Procedure Rules 2005 provide (Rule 36.11) that unless the Court otherwise orders, a judgment or order is taken to be entered when it is recorded in the Court's computerised court record system. Setting aside and variation of judgments or orders is dealt with by Rules 36.15, 36.16, 36.17 and 36.18. Parties should in particular note the time limit of fourteen days in Rule 36.16.]

HEADNOTE [This headnote is not to be read as part of the judgment] Mr Brendan Hobson, the respondent, suffers from Noonan Syndrome, a genetic disorder that prevents normal development in various parts of the body. As a result of that disorder, Mr Hobson's ability to fill his lungs with air, and hence to breathe, was restricted. Without surgical intervention, his prognosis was grave. Surgery to correct this problem was designed to take place in two stages. The first operation was successful. The second, which occurred on 17 November 2009, had to be terminated before its intended conclusion. As a result of that operation, Mr Hobson became a paraplegic. Mr Hobson initiated proceedings claiming damages for negligence. His claims ultimately proceeded against the principal surgeon, Dr Randolph Gray, and the principal anaesthetist, Dr Christopher Sparks. Dr Gray is an experienced specialist orthopaedic/spine surgeon and Dr Sparks is an experienced specialist anaesthesiologist. After an 11 day hearing before Harrison J in the Common Law Division of the Supreme Court, his Honour found that Drs Gray and Sparks had breached the duties of care that they owed to Mr Hobson and were liable in negligence for damages in the amount of $3,828,075. The basis of the decision against both doctors was that, in light of adverse blood gas readings for carbon dioxide obtained in the course of the operation, they should have caused the operation to be terminated earlier than occurred. His Honour held that if the operation had been so terminated, Mr Hobson would not have suffered a significant cardio-vascular collapse during the operation at about 21:30, his spine would not have been damaged and he would not have become a paraplegic. Drs Gray and Sparks each appealed against the primary judge's decision on liability. As well as contending that the primary judge erred in finding that they acted negligently, the appellants relied, as they did at first instance, on sections 5 I and 5 O of the Civil Liability Act 2002 (NSW). The appellants also appealed against his Honour's decision on damages in three limited respects. They contended that his Honour erred in the allowances that he made for past and future domestic care, and for motor vehicle expenses. By majority (Simpson JA dissenting), the Court dismissed Dr Sparks' appeal with costs. The Court unanimously allowed Dr Gray's appeal. In relation to Dr Sparks' appeal: (1) Breach of duty was established. Per Basten JA at [93]: "Dr Sparks was faced with a difficult intraoperative choice. However, it was not one which required an instantaneous decision, nor one which required further information or advice. The patient's metabolic decline was continuing despite Dr Sparks having taken every available step to alleviate the condition whilst the operation proceeded. However, whilst the operation continued, the patient was heading for cardiovascular failure. The operation was expected to last for some four hours; at 9pm the operation was only half completed, on that timescale. (The orthopaedic experts stated that it had 2-4 hours to go.) The decision to allow it to continue for 30 minutes after Dr Sparks had sought help from two experienced anaesthetists, without success, involved more than an erroneous clinical judgment; the trial judge was correct to find a breach of duty of care" (citations omitted). Per Macfarlan JA at [181] and [182]: "Dr Sparks made an unreasonable decision to ignore a serious and imminent intra-operative danger to Mr Hobson's well-being when Dr Sparks knew that the other risk with which he was concerned (namely the risk to Mr Hobson if the operation were not completed) did not have the same immediacy…It was not for Dr Sparks to assess the urgency of the operation and decide that it justified a serious and immediate intra-operative risk to Mr Hobson being ignored, at least not without consulting Dr Gray who, as principal surgeon, was head of the surgical team." Per Simpson JA (dissenting) at [359]: "The medical evidence does not…support a finding that, in failing to direct the termination of the surgery before 21:28, Dr Sparks failed to exercise reasonable care and skill. The decision Dr Sparks had to make (on a continuing basis throughout the surgery) involved the exercise of clinical judgment…The respondent bore the onus of establishing that Dr Sparks' decision not to direct the termination of the surgery before that time represented a departure from the standard of care and skill required of a specialist anaesthetist. That onus was not discharged. The medical evidence falls well short of permitting a conclusion to that effect." (2) Section 5 I of the Civil Liability Act 2002 (NSW) did not provide a defence to Dr Sparks (Simpson JA dissenting). (3) Section 5 O of the Civil Liability Act 2002 (NSW) did not provide a defence to Dr Sparks. Discussion by the Court of the correct interpretation of s 5 O. McKenna v Hunter & New England Local Health District [2013] NSWCA 476; (2013) Aust Torts Rep 82-158 considered. Hunter and New England Local Health District v McKenna (2014) 253 CLR 270; [2014] HCA 44 referred to. In relation to Dr Gray's appeal: Per Macfarlan JA at [201]: "[T]he surgery that took place on 17 November was complex, protracted and difficult. It was Dr Sparks' role to monitor indicators of Mr Hobson's condition during the surgery, the two main ones being Mr Hobson's blood oxygenation and blood pressure, although other indicators were relevant. At least in respect of the other relevant indicators, Dr Gray was entitled to rely on Dr Sparks to inform him of any matter of concern without Dr Gray making any inquiry. There is no evidence that Dr Sparks did so in the period 20:50 to 21:20, and the evidence did not indicate that any matter came to Dr Gray's notice during that time that should have caused him to make an inquiry as to Mr Hobson's carbon dioxide level. Without such information, Dr Gray was not negligent in failing to direct termination of the operation during that period. When Dr Sparks did advise termination of the operation at around 21:25, Dr Gray promptly did so. Dr Gray's appeal on liability therefore succeeds." In relation to both appeals: The challenges to the primary judge's damages assessment were rejected.

Judgment 1. BASTEN JA: The respondent, Brendan Hobson, was born with Noonan Syndrome, one feature of which was a serious curvature of the spine resulting in a reduced chest cavity, particularly on the left side. In the course of 2009, Mr Hobson suffered increasing breathlessness and a pattern of restrictive airways disease. Corrective surgery was undertaken which involved a two-stage operation intended to relieve the pressure on the chest cavity by straightening the spine. 2. The first stage of the operation took place on 13 November 2009, which was completed uneventfully in a surgical sense. The second stage was planned for 10 days later. However, whilst Mr Hobson was in the intensive care unit his respiratory condition deteriorated as a result of the left main airway (bronchus) becoming obstructed, with the result that pneumonia developed in the left lung. The second stage of the operation was brought forward to the evening of 17 November 2009. 3. The procedure was expected to take some four hours, commencing shortly after 7pm. However, the senior anaesthetist, Dr Christopher Sparks, requested the surgeons to terminate the procedure at about 9.25pm, when the patient's blood pressure and oxygen levels had dropped dramatically. Once the wound had been closed the patient, who had been in a prone position on the operating table, was returned to a supine position, whereupon his condition improved. Nevertheless, there had been a severe ischaemic collapse in his spinal column resulting in paraplegia. 4. The operation was later completed successfully, but Mr Hobson did not recover the use of his lower limbs. 5. Mr Hobson commenced proceedings against the hospital and various members of the team who operated on him, alleging negligence in various respects. In November 2016 a trial was conducted before Harrison J in the Common Law Division. On 17 May 2017 judgment was delivered for the plaintiff against the principal surgeon, Dr Gray, and the principal anaesthetist, Dr Sparks. Mr Hobson was awarded damages. [1] The particular of negligence which was upheld with respect to both practitioners was the failure to terminate the operation no later than 9.15pm that evening. 6. Both the medical background and the procedural background have been fully explained in other judgments. For the reasons given by Macfarlan JA, it is clear that, with respect to the single particular of negligence which was upheld, the primary responsibility lay with the anaesthetist, Dr Sparks. I agree that the finding of negligence on the part of Dr Gray was not justified and Dr Gray's appeal should be allowed. 7. The situation with respect to Dr Sparks has led to differing conclusions. The following reasons address the case against Dr Sparks and the basis on which he has challenged the decision below. 8. Much of the relevant material was set out clearly and comprehensively by the trial judge in reasons the bulk of which are not the subject of challenge on this appeal. Despite the complexity of the medical evidence, the number of experts called and the somewhat variable course taken on behalf of the plaintiff during the trial, the issues raised on the appeal are circumscribed; the trial judge rejected some 13 particulars of negligence in respect of which there is no notice of contention. [2] It is convenient to commence by identifying the relevant grounds of appeal.

Dr Sparks: grounds of appeal 1. Dr Sparks pleaded seven grounds of appeal, six of which related to liability and the seventh to aspects of the assessment of damages. 2. Grounds 1 and 2 alleged error in the application of s 5O of the Civil Liability Act 2002 (NSW), set out in the next part of these reasons. It is convenient to set the grounds out in full. "1. The primary judge erred in failing to find, pursuant to section 5O of the Civil Liability Act 2002 (NSW), ("the Act") that the appellant did not incur a liability in negligence, in circumstances where: a. the appellant adduced expert evidence to the effect that he acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice; b. that evidence was not challenged; and c. the primary judge did not find that the peer professional opinion is irrational and could not, for that reason, be relied on. 2. The primary judge erred in failing to determine the standard of care according to the evidence of what was, in 2009, widely accepted in Australia by peer professional opinion as competent professional practice." 1. The syntax of ground 3 was obscure, but it appeared to be directed to s 5I of the Civil Liability Act. In short, it alleged that the respondent suffered harm as a result of the materialisation of an inherent risk which could not be avoided by the exercise of reasonable care. The risk was identified as "risk of suffering spinal cord ischemia". 2. Ground 4 alleged that the judge failed to identify "the risk of harm" against which the appellant ought to have taken precautions. Ground 5 alleged that the judge had wrongly held there was a breach of duty merely because the risk of harm could have been avoided by doing something in a different way. Ground 6 asserted in broad terms that the time for terminating the procedure was a matter of clinical judgment for the anaesthetist and that allowing the operation to proceed for some 15 minutes after the last moment at which it should reasonably have been terminated (as identified by the trial judge) did not constitute a breach of duty. 3. Grounds 1 and 2 are central to the appeal and it is convenient to turn to the operation of s 5O of the Civil Liability Act.

Civil Liability Act, s 5O 1. Both appellants appealed from the rejection by the trial judge of their respective defences based on s 5O of the Civil Liability Act. There are a number of reasons for addressing the defence separately in each case. First, Dr Gray originally pleaded the section with five particulars, three of which appeared to be directed to s 5I. Neither of the other two potentially relevant particulars addressed the termination of the operation. [3] Dr Sparks, by contrast, originally pleaded the section, but without any particulars at all. [4] Secondly, although both appellants addressed the issue in written submissions at trial, they did so in somewhat disparate terms. [5] Thirdly, the nature of each defence case turned primarily upon the evidence of the expert witnesses practising in the field of the particular specialist. 2. Before addressing these separate circumstances it is convenient to consider the scope and operation of s 5O. The section is located in Pt 1A of the Civil Liability Act dealing with "Negligence". The Part does not constitute a comprehensive statement of the principles governing the tort of negligence, but identifies in separate divisions a number of specific principles. Section 5O appears in Div 6, entitled "Professional negligence". The primary principle is stated in subs (1), but it is convenient to set out the whole of the section, including the subsidiary provisions: 5O Standard of care for professionals (1) A person practising a profession (a professional) does not incur a liability in negligence arising from the provision of a professional service if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice. (2) However, peer professional opinion cannot be relied on for the purposes of this section if the court considers that the opinion is irrational. (3) The fact that there are differing peer professional opinions widely accepted in Australia concerning a matter does not prevent any one or more (or all) of those opinions being relied on for the purposes of this section. (4) Peer professional opinion does not have to be universally accepted to be considered widely accepted. 1. The section envisages a conflict in the evidence as to whether the defendant's conduct was accepted by his or her peers as "competent professional practice." In order to establish negligence, there will usually need to be expert evidence called by the plaintiff to the effect that the defendant failed to exercise reasonable care and skill in providing a relevant service. Under the general law, the defendant would seek to challenge that evidence by calling expert opinion to a contrary effect. For the plaintiff to succeed, the court would need to be satisfied on the probabilities that the appropriate standard was that for which the plaintiff's experts contended. That position has been varied by s 5O(1); although expressed in the passive voice ("if it is established that …"), it has been broadly accepted that the section provides a defence. [6] 2. Despite the common acceptance of the provision as a "defence", that characterisation gives rise to difficulty. To be a defence carries the implication that the plaintiff must establish breach according to the general requirements of s 5B of the Civil Liability Act, following which the practitioner bears the burden of establishing that his or her conduct amounted to "competent professional practice" in the terms of s 5O(1). The heading of the section ("Standard of care for professionals") indicates its purpose. Although the heading is not part of the Act, [7] it may be taken into account as extrinsic material in construing the provision, in accordance with s 34(1) of the Interpretation Act. In any event, it is tolerably clear that the provision sets a standard. However, if the standard is met, it follows that the conduct was not negligent. 3. Accordingly, once s 5O is invoked, arguably the general exercise required by s 5B becomes otiose. There can only be one standard against which to judge the conduct of a professional defendant, although that standard may depend upon the resolution of conflicting evidence called by the plaintiff and the defendant. It is only if one takes the plaintiff's evidence in isolation that a two-stage process, involving the assessment of the plaintiff's claim followed by assessment of an affirmative defence, will arise. However, in a practical sense, that is not how the dispute should be determined. Rather, a judgment will be given based on all of the evidence. Nor is the exercise helpfully clarified by speaking of shifting burdens of proof. The question for the trial judge is ultimately whether the plaintiff has established that the conduct of the defendant failed to comply with the relevant standard of care. This approach is consistent with Dobler and is not to say that a plaintiff must seek out and negative opinions inconsistent with those of the experts on whom he or she relies. [8] Beyond that proposition, Dobler did not turn upon the onus of proof. [9] 4. This approach obtains support from an understanding of s 5O in its historical context. Prior to the enactment of s 5O, Australian courts identified the standard of care in medical negligence cases according to the principles set out in Rogers v Whitaker: [10] "In Australia, it has been accepted that the standard of care to be observed by a person with some special skill or competence is that of the ordinary skilled person exercising and professing to have that special skill. But, that standard is not determined solely or even primarily by reference to the practice followed or supported by a responsible body of opinion in the relevant profession or trade." 1. This statement rejected the approach then applied in the UK [11] by reference to a direction given to a jury by McNair J in Bolam v Friern Hospital Management Committee. [12] As Lord Scarman explained in Sidaway v Board of Governors of Bethlem Royal Hospital: [13] "The Bolam principle may be formulated as a rule that a doctor is not negligent if he acts in accordance with a practice accepted at the time as proper by a responsible body of medical opinion even though other doctors adopt a different practice. In short, the law imposes the duty of care: but the standard of care is a matter of medical judgment." 1. Lord Scarman himself preferred a different approach: [14] "In my view the question whether or not the omission to warn constitutes a breach of the doctor's duty of care towards his patient is to be determined not exclusively by reference to the current state of responsible and competent professional opinion and practice at the time, though both are, of course, relevant considerations, but by the court's view as to whether the doctor in advising his patient gave the consideration which the law requires him to give to the right of the patient to make up her own mind in the light of the relevant information whether or not she will accept the treatment which he proposes." 1. Australian authority, as explained by Gleeson CJ in Rosenberg v Percival, [15] adopted the dissenting view of Lord Scarman by which "the relevance of professional practice and opinion was not denied; what was denied was its conclusiveness." The Australian approach was not confined to cases of warnings and medical advice; it extended to diagnosis and treatment. [16] 2. However, the language of s 5O differs from Bolam, which referred to a practice accepted as "proper" by a "responsible body of medical men". Lord Scarman also referred to "responsible and competent professional opinion". The differences may not have practical significance. 3. In Dobler, Giles JA stated : [17] "Section 5O may end up operating so as to determine the defendant's standard of care, but the standard of care will be that determined by the court with guidance from evidence of acceptable professional practice unless it is established (in practice, by the defendant) that the defendant acted according to professional practice widely accepted by (rational) peer professional opinion." Ipp JA and I agreed. On reflection, this passage may be open to misunderstanding. It is true that s 5O will not be engaged unless there is evidence of a widely accepted professional practice supporting the defendant's conduct, but where there is such evidence, unless it can be rejected by the trial judge, it will fix the relevant standard; there cannot be two legally supportable standards operating in the one case. 1. There remains a question as to the extent to which the trial judge has a discretion to reject evidence of a widely accepted professional practice. The judge may dismiss "peer professional opinion" as "irrational", in accordance with subs 5O(2). By contrast, the older cases, while tending to use transferred epithets, refer to opinions of responsible and competent practitioners in the field. It may be that the reference in s 5O to "peer professional opinion" is to be so understood. But then it is difficult to understand how an irrational opinion could qualify as a relevant peer opinion. 2. More importantly, the provision raises the possibility of a negative inference, namely that the court may not reject an opinion even though satisfied that it is unreasonable (though not irrational), or otherwise not one the court would itself adopt. Such a general negative inference should not be inferred; there will be other questions which will arise. 3. First, there will be a question as to whether the evidence of one or two experts can satisfactorily establish opinions which are "widely accepted" in circumstances where such a view is contradicted by other evidence. No doubt evidence of "general professional opinion", in addition to the personal opinion of the expert, is admissible in such circumstances. [18] 4. Secondly, it will be a matter for the court to assess the significance of particular evidence. Evidence may be at a greater or lesser level of generality. At a high level of generality it may readily be accepted that an opinion is widely held amongst peers of the practitioner. However, the standard so identified may not assist greatly in resolving the particular case. On the other hand, the more particular the opinion, based on the specific circumstances of the case, the more difficult it may be to establish an opinion which can be described as "widely accepted" among fellow practitioners. Accordingly, whether or not evidence of medical opinion is properly described as conclusive in a particular case will depend upon a range of factors and not merely the fact that it can properly be described as not irrational. 5. Subsections (3) and (4) do little more than explain what might otherwise readily have been inferred, namely that for an opinion to be "widely accepted" it need not be "universally accepted" and, if not universally accepted, there must be more than one opinion and may be more than one which is widely accepted. If the court is satisfied that the defendant's conduct is considered competent according to widely accepted peer professional opinion, that opinion provides a standard against which to assess the claim. 6. At trial, both practitioners raised s 5O as a defence. Counsel for the plaintiff treated the reasoning of this Court in McKenna v Hunter & New England Local Health District [19] as an effective answer to the defence. In McKenna Macfarlan JA stated that: [20] "To establish a defence under s 5O a medical practitioner needs to demonstrate, first, that what he or she did conformed with a practice that was in existence at the time the medical service was provided and, secondly, to establish that that practice was widely, although not necessarily universally, accepted by peer professional opinion as competent professional practice." On the appeal, counsel for Dr Sparks submitted that McKenna was wrong in holding that it was necessary to demonstrate the existence of "a practice" extant at the time of the conduct in question. 1. Although it is uncertain how this reasoning in McKenna will operate in particular cases, there is a risk in reformulating the statutory language. To speak of "a practice" adopted by a group of professional persons suggests a regular course of conduct adopted in particular circumstances. By contrast, the phrase "competent professional practice" is apt to cover the whole gamut of professional services provided by the practitioner, whether or not the particular circumstances have arisen sufficiently often to result in an established practice. For example, although opinions may differ as to the conclusion to be drawn, there is no grammatical or semantic difficulty in describing an argument run by counsel in a novel case as demonstrating competent or incompetent professional practice. The same judgment may be offered about the failure of counsel to call a defendant in a criminal trial, where no settled practice exists. Where an acquittal depends on establishing an affirmative defence and there is no other evidence to support the defence, it may be described as incompetent professional practice not to call the defendant who could have given such evidence. Where an opinion is given and challenged, it will be supported (or attacked) not by reference to some established practice, but by reference to how an assessment of the circumstances (which may be unique) would be undertaken by a knowledgeable and experienced practitioner. 2. There are other reasons for thinking that the reference to "competent professional practice" does not require evidence of "a practice". First, it is the "manner" in which the defendant acted which must be the focus of the opinion. Secondly, if it were necessary to establish a practice, one might expect subs (3) to refer to "opinions … concerning that practice", rather than "opinions … concerning a matter". 3. To take an example closer to the present case (but still hypothetical) an anaesthetist might allow an operation to proceed on the basis that two indicators remained within acceptable limits but a third indicator did not. An expert might express an opinion that such conduct was not competent practice, not because he or she had experienced the same circumstance in the past, or had read about it in a textbook, but because basic principles of human physiology led to that conclusion. 4. Accordingly, although the language used in McKenna may well sufficiently describe many circumstances in which s 5O is invoked, I would not understand it as a general proposition as to the constraints imposed by s 5O(1). 5. If that understanding is too restrictive and it is necessary to go further, I would not follow McKenna. The decision in McKenna having been overturned in the High Court, [21] the reasoning of the majority in this Court is no longer binding. As Kirby J noted in Garcia v National Australia Bank: [22] "It is fundamental to the ascertainment of the binding rule of a judicial decision that it should be derived from (1) the reasons of the judges agreeing in the order disposing of the proceedings; (2) upon a matter in issue in the proceedings; (3) upon which a decision is necessary to arrive at that order. Thus, the opinions of judges in dissent are disregarded for this purpose, however valuable they may otherwise be." 1. When the decision of an intermediate court of appeal is overturned by the High Court, the reasoning of the majority is no longer dispositive, even if the High Court does not directly reject it, as it did not with respect to the interpretation of s 5O in McKenna, having determined the appeal on a different point. 2. There is some irony in the fact that the primary support for this conclusion is often sourced to a brief statement by Aickin J in dissent in Federal Commissioner of Taxation v St Helens Farm (ACT) Pty Ltd [23] stating: "I should add that there is no basis on which one point in the judgment of a primary court should be regarded as authoritative where the judgment is reversed on other grounds." 1. Given that the reasons of the intermediate court in a case where the decision has been reversed are no longer dispositive, they are analogous to the reasoning of a dissenting judge. Allsop P explained in Holmes a Court v Papaconstuntinos [24] that dissenting judgments "may contain valuable discussions of legal principle", but that is "a different thing to being taken as an exposition of the common law to be applied." The same proposition applies with respect to discussion of statutes. 2. The position would, of course, be quite different if the High Court, despite reversing the decision in this Court in McKenna, had approved the reasoning with respect to s 5O. The reasoning would not then form part of the ratio, but it would clearly obtain the authority of dicta of the High Court. However, that did not happen in the present case. The High Court held that the plaintiff must fail on the basis that there was no duty of care owed to relatives of the deceased. The Court continued: [25] "Consideration of those other issues, about ss 5B, 5O, 43 and 43A of the [Civil Liability Act], should await a case in which it is necessary to examine them." 1. While the reasoning of this Court in McKenna as to the scope and operation of s 5O is not to be disregarded, there is no obligation on this Court, as a matter of precedent, to follow it. For the reasons set out above, in my view it is too restrictive. [26]

Civil Liability Act, s 5I 1. Dr Sparks also called in aid the exclusion from liability for the materialisation of an inherent risk, as set out in s 5I of the Civil Liability Act. The section provides: 5I No liability for materialisation of inherent risk (1) A person is not liable in negligence for harm suffered by another person as a result of the materialisation of an inherent risk. (2) An inherent risk is a risk of something occurring that cannot be avoided by the exercise of reasonable care and skill. (3) This section does not operate to exclude liability in connection with a duty to warn of a risk. 1. The scope and operation of the provision has been the subject of careful consideration in earlier decisions, including Paul v Cooke. [27] The apparently simple language of the provision is fraught with difficulties. 2. On one reading of subs (2), that which "cannot be avoided" by the exercise of reasonable care is the "risk"; the alternative reading is that it is the materialisation of the risk which cannot be avoided by exercise of reasonable care. To speak of "avoiding" a risk is meaningful in some circumstances, but not in others. Ordinary usage would suggest that it is the occurrence (the materialisation of the risk) which may or may not be "avoided". Context suggests that that is the intended meaning because the provision only operates where a person has suffered harm as a result of the "materialisation of an inherent risk." 3. The next problem stems from the use of the words "cannot be" avoided. A risk is less than a certainty; it may be quantified in a particular case at, say, 25%. In three out of four cases the harm will not materialise and in one sense "can" be avoided. However, the section should be understood as referring to the exercise of skill having no causal consequence in terms of the outcome. Thus, in a sense, the provision may be read as operating where the skill of the surgeon does not affect the risk of an adverse outcome. 4. Of course, the application of s 5I will only arise in circumstances where (staying with the medical example) the patient has had an adverse outcome, in which case liability will depend upon establishing negligence and causation. Assuming negligence, the plaintiff will fail if she cannot demonstrate a causal connection between the negligence and the harm. In that case, s 5I is not required by the defendant; if causation is established, s 5I is not engaged. 5. Rogers v Whitaker is often cited as a paradigm of an inherent risk. The patient had an operation on her right eye, which resulted in her losing her sight in her left eye as a result of a condition known as sympathetic ophthalmia. Evidence suggested that the risk materialised in fewer than one in 10,000 cases. The operation had been carried out with the required skill and care. Rogers itself involved a failure to warn and thus s 5I would not have applied. [28] 6. There may be cases, of which Paul v Cooke was one, where negligence may be conceded and the case will turn on causation. However, as Leeming JA explained, where s 5I is raised, "it unquestionably remains for the plaintiff to establish s 5D legal causation, and the logical consequence of so doing may (and often will be) to negate s 5I." [29] 7. This is not a case where the risk of harm was less than 50%, so that, had the negligence not occurred, the operation would have been conducted on a different occasion when, on the probabilities, the harm that in fact occurred would not have occurred. 8. Section 5I has no application in the present case. The risk which accompanied the surgery was the neurological collapse of the spinal column which in fact occurred. There is no doubt that if the operation had ceased at a point in time before the collapse occurred (which was probably shortly before the operation in fact ceased) the risk would not have materialised; the harm would not have occurred. That result would have been achieved in the exercise of reasonable care and skill. The question for the determination of the Court was whether the continuation of the operation involved a failure to exercise reasonable care and skill. Because the definition of "inherent risk" in s 5I assumes that the exercise of reasonable care and skill would not affect the outcome, it is not clear how the section was said to be engaged in the present case.

Evidence and findings at trial 1. There were five methods adopted for the monitoring of the patient's condition during surgery. These were (a) blood pressure, (b) oxygen levels in blood, (c) CO2 levels in blood, (d) exhaled CO2 levels and (e) spinal cord monitoring. The last (spinal cord monitoring) was abandoned, but that proved to be only indirectly relevant to breach of duty; it may conveniently be addressed first. Dr Sparks based his decision-making on the first two parameters; a critical question was whether he should have paid greater attention to the CO2 levels.

(a) spinal cord monitoring 1. It is convenient to consider first the significance of the spinal cord monitoring. The importance of such monitoring arose from the fact that part of the arterial blood supply to the spinal cord had been diminished through the first procedure. An episode of low blood pressure (hypotension) was liable to place the spinal cord at risk through loss of blood supply. A number of criticisms were made of the monitoring procedure. First, it was important to obtain a baseline reading. The neurophysiologist responsible for the monitoring, Associate Professor Jim Lagopoulos gave evidence that he arrived at the theatre after the procedure was already underway. He said that a normal baseline reading was not able to be established. It was common ground that at or about 8.35pm Dr Sparks administered vecuronium to improve the patient's ventilation. The drug, a muscle relaxant, led to the discontinuation of the spinal cord monitoring as it had become ineffective. 2. There was inconsistent evidence given at the trial as to whether the readings from the monitoring were ever normal and as to whether Dr Gray or Dr Sparks was advised of the fact that they were abnormal, to the extent that they were. However, the expert evidence did not support the proposition that the surgery should have been terminated in light of the results of the monitoring. Rather, the concern focused on the fact that the monitoring ceased at about 8.35pm, when vecuronium was administered. At that stage, Dr Sparks believed that there was a problem with ventilation, and hoped that administration of vecuronium would correct the problem. The trial judge accepted that this was a reasonable step to take. He continued: [30] "However, the significant compromise in those circumstances was that the spinal cord monitoring was immediately neutralised by its administration and any form of spinal insult that spinal cord monitoring might otherwise have been expected to highlight would remain dangerously undetected. In other words, Dr Gray and Dr Sparks were effectively trading off any concern they might have had that Mr Hobson may be neurologically compromised if the surgery proceeded in the absence of spinal cord monitoring against the possibility that he might die if the corrective surgery were discontinued." 1. The judge then considered what warnings might have been available had the spinal cord monitoring continued after 8.30pm. Dr Westbrook had given evidence that "had spinal-cord monitoring been properly established in a timely manner that there would have been advanced warning to the clinicians that spinal cord perfusion was threatened particularly during the transient, earlier episodes of hypoxaemia." [31] Dr Michael Johnson, an orthopaedic surgeon, gave evidence that he would have "insisted that spinal cord monitoring was available." [32] Dr Peter Heath also gave evidence of the importance of effective monitoring. In effect there was a wealth of evidence from the plaintiff's experts that spinal cord monitoring was an important safety mechanism in circumstances where blood supply to the spinal cord was reduced by the earlier surgery, and where even transient elements of hypotension suggested cardiovascular instability which needed to be monitored. On the other hand Dr Geoffrey Askin, who was called by Dr Gray, stated: [33] "MEP monitoring in this case would not have allowed remedial action given that the only remedial action that allowed the patient to restore blood pressure and PCO2 was to turn the patient supine. Having MEPs running during the time of the physiological crisis would not have expedited the termination of the procedure and changing the patient's position at all. Hence, the loss of MEPs would not have changed the outcome." 1. The trial judge had extracted, at [66] and [67], lengthy extracts from the evidence of Dr Peter Silbert, a neurologist and expert in spinal cord monitoring. Dr Silbert's conclusion was that, had spinal cord monitoring continued, it would not have detected abnormalities prior to 9.25pm, which was the time at which the collapse in other indicators led Dr Sparks to request that the surgery end. The trial judge placed weight on that evidence, and the evidence of other experts to similar effect. The consequence was that although the absence of spinal cord monitoring should have led to caution on the part of the anaesthetist and the surgeon, its presence would not have altered the outcome. This conclusion was expressed in two parts. First, at [223], the judge concluded that continuing the operation beyond 8.30pm was perfectly reasonable. Allowing that use of vecuronium was also a reasonable step, "there was … at the time no useful place for spinal cord monitoring." [34] 2. The second stage in the argument was addressed at [243] in the following terms: "Sixthly, there was a need to be particularly mindful of the consequences for Mr Hobson of his rapidly deteriorating ventilation by reason of the fact that spinal cord monitoring was absent or effectively neutralised. For present purposes it does not matter which it is. Indeed, I accept the opinion of Dr Silbert that he did not believe that SSEPs and MEPs would have detected significant spinal cord electrophysiological abnormalities prior to 21.25. In that sense I am not satisfied that the absence of spinal cord monitoring for whatever reason properly informs or supports a finding of negligence by either defendant. Its absence or ineffectiveness was a fact of life in the operating theatre at 20.30 and at the very point at which Dr Sparks telephoned Dr Barratt. It was however to my mind a critically significant factor that not only enlivened, but in fact heightened, the need to act conservatively and to proceed expeditiously. It told against the appropriateness of taking an expectant approach when the solution to Mr Hobson's difficulties had not emerged or was not understood."

(b) measuring other conditions 1. Putting monitoring to one side, there were four other measurable parameters taken into account. Dr Sparks relied primarily on arterial blood pressure and oxygen saturation in the blood, as supporting continuation of the surgery. Until those fell below acceptable limits, he allowed the surgery to continue. 2. The challenge to his decision-making was based upon his failure to act upon the concerns raised by the other parameters demonstrating that carbon dioxide was not being removed from the blood stream. There is no doubt that the readings caused him serious concern and led to him telephoning from the operating theatre a senior colleague, Dr Stephen Barratt with whom Dr Sparks had performed a bronchoscopy at the intensive care unit during the day before the operation. It was agreed that the telephone call was at approximately 8.50pm. Dr Barratt gave the following evidence in an affidavit: [35] "11. Dr Sparks told me that Mr Hobson was in the prone position on a Jackson table during the surgery. In my view, if the breast plate of the Jackson Table was pressing on Mr Hobson, the cardiac compression would generate potential for hypotension. 12. Dr Sparks expressed his concern about a high arterial carbon dioxide at the time, I think he said approximately 65 mmHg. This is about 50% more than normal. This usually means inadequate ventilation and this issue had been excluded with multiple bronchoscopies, checking for breath stacking and pneumothorax. However, at the time Mr Hobson's end tidal carbon dioxide was only 30-25mmHg which means a significantly increased dead space ventilation. Inadequate ventilation on its own does not explain this. Therefore, I proposed to Dr Sparks that maybe a pulmonary artery was being compressed along with possible cardiac compression which would mean he would have a section of his lung which was being ventilated, but not perfused. The telephone call abruptly ended when Dr Sparks said 'I gotta go'." 1. The trial judge summarised the plaintiff's case at trial in the following terms: "[124] Mr Hobson submitted that a failure to consider factors beyond oxygen saturation and blood pressure was indicative of a standard of medical practice below the standard required in Australia in November 2009 of a reasonably competent anaesthetist or orthopaedic surgeon, performing spinal surgery in the particular method adopted to treat Mr Hobson. … [125] Mr Hobson was in respiratory difficulty from the commencement of the surgery and the surgical team had trouble ventilating him throughout. His metabolic state, especially as reflected in his blood gasses, was also poor from the start and continually deteriorated during the surgery. [126] Blood gasses demonstrated a clear deterioration in Mr Hobson's metabolic state as the surgery progressed. Samples taken at 20.08 and 20.21 had by then already demonstrated a very high carbon dioxide level despite various attempts at pulmonary ventilation with a double lumen tube. This was causing significant respiratory acidosis. From the early stages of the surgery, blood gasses disclosed evidence of an increasing lactate level suggesting inadequate organ perfusion. Blood gas samples at 20.37 and 20.51 demonstrated significant further deterioration of all parameters. [127] A reasonably competent anaesthetist would have concluded that Mr Hobson was suffering a profound respiratory and metabolic acidosis. Both Dr Sparks and Dr Gray were aware of this dangerous downward spiral in Mr Hobson's metabolic state. [128] By 20.50 Dr Sparks had tried various means of reversing this deteriorating trend without success. In particular, maintenance of blood pressure and ventilation at reasonable levels after transient drops had failed to address Mr Hobson's dire and deteriorating metabolic state. [129] As noted above, Dr Sparks spoke to Dr Barratt over the telephone at 20.50 or thereabouts. Dr Barratt correctly suggested to Dr Sparks that the breastplate of the Jackson table may have been pressing on Mr Hobson, creating cardiac and pulmonary artery compression. This meant that a section of lung was being ventilated but not perfused. Dr Sparks agreed with this analysis. Mr Hobson submitted that a reasonably competent anaesthetist would have called a stop to the surgery by this time at the latest. Had the surgery been paused or halted at that, or any earlier time, and Mr Hobson turned supine, he would not have suffered spinal cord damage." 1. The findings of the trial judge in relation to this aspect of the case appeared as the fifth element in a series: [36] "Fifthly, even if there was arguably no single unambiguous indication for stopping the surgery before the decision to do so was made, there were several factors which together certainly gave that indication. As Mr Hobson emphasises, the evidence of Dr Barratt, who was after all the expert to whom Dr Sparks turned when his options appeared to be evaporating, emphasises the importance of heeding several factors in combination. It is reasonably clear that Dr Barratt's telephone input inspired the events that followed it. The attending doctors undoubtedly had access to several significant indicators of Mr Hobson's condition, even if none taken alone pointed only in one direction. The combination of these factors provided a different perspective. The earlier indications available from Mr Hobson's vital signs appeared to be that any deteriorations that were observed, in particular, episodes of hypoxia and hypotension occurring at or about 18.50, 19.10 and up until about 20.35, some of which were severe, were transient and recoverable but not such as to indicate that continuing with the surgery could not be justified. Up until about 20.35, Dr Gray and Dr Sparks were, in effect, permissibly taking an expectant approach, in the absence of material that indicated only one possible course of action. That position changed very shortly thereafter." 1. On the appeal, Dr Sparks challenged the sentence italicised above. However, that sentence could be omitted without interfering with the process of reasoning. 2. The judge then set out in some detail Dr Westbrook's evidence, together with the responses of Dr Forrest and Dr Manasiev. He referred to Dr Sparks' own evidence and to the expert evidence of two orthopaedic surgeons in the following terms: [37] "As I have earlier noted, the orthopaedic surgeons in their joint report indicated that the surgery should have ceased 'when the anaesthetists reached the stage that they were unable to maintain satisfactory cardio respiratory parameters'. The orthopaedic surgeons made no precise reference to a time when the surgery should have ceased. Satisfactory cardio respiratory parameters were not being maintained by 20.30." 1. Before turning to the evidence of Dr Barratt, on whom the trial judge placed some weight, it is convenient to return to the evidence given by Drs Westbrook and Forrest addressing their joint report. Dr Westbrook had set out in his affidavit and a chart annexed to the affidavit the evidence of steadily deteriorating metabolic conditions and their consequence. In responding to questioning from the plaintiff's counsel he stated: [38] "So – well, so the carbon dioxide level at 19.13 was, as I say, 64, well – well above the upper limit of normal of 48. Subsequently it went [to] 69, so it steadily increased until it really reached a peak at 20.51. But even at 20.37 and 20.21 it was up to 70 which was, as I say, well above the normal limits. Now, the consequence of that is that the patient had become increasingly [acidotic] and that was further aggravated by what's referred to as a metabolic acidosis. That – so that was an accumulation of acids in the blood stream most likely due to inadequate perfusion of other organs. So by 20.37 the patient had a pH of 7.027 which really is a serious acidosis, a mixed metabolic and respiratory acidosis, the consequences of which are depressed myocardial function and other depressed cellular functions in the body. MENZIES: Could that lead to some result adverse to the patient at that point? WESTBROOK: Well, if – certainly were it to continue to deteriorate which it – of course it did at 20.51 and 21.01, the pH was even lower and at 21.13 lower still. That, coupled with the compression of the great vessels in the chest, you know, there was an inevitable deterioration towards to the eventual collapse at … 21.20 or thereabouts. I think … the problem for the anaesthetist is they didn't have anything they could do to improve the situation. They were doing everything they possible could in terms of ventilation of the lungs, in terms of maintaining h[a]emodynamics. And despite these measures, the acidosis was deteriorating. MENZIES: You've already expressed an opinion that, in the light of that deterioration …, that the collapse that occurred [at] 21.33 or thereabouts was inevitable at some point. … When did that inevitability arise? Or put another way, in as much as it was inevitable and you've already said the surgery should have been stopped, at what point then do you say the surgery should have been stopped? WESTBROOK: I – I mean I think at 2021 things were looking pretty grim but certainly at 2037 with a pH of 7 and an increasing lactate I – it's my view the surgery should have been abandoned at that point." 1. Dr Forrest agreed that with "a benefit of hindsight I think you couldn't argue that [it] would have been preferable to abandon the surgery earlier than … the time that it was abandoned." [39] He was challenged as to whether that conclusion could only be advanced with hindsight. He referred to the steps which were taken, the difficult choice the doctors were required to make given the possible effects of abandoning the surgery, and the attempts made to correct the underlying cases of metabolic acidosis. He continued: [40] "Now, that in fact proved to be unsuccessful, because his carbon dioxide continued to climb, so as his carbon dioxide reached a level of over a hundred at – at – 2051. And I think really, the key to this is that – is that the difficulty in ventilation was already one of the key factors that was aggravating his metabolic acidosis because as carbon dioxide climbed, that led to an increase in his pulmonary-vascular resistance, which is the – basically the impedance against which the right ventricle has to eject. That in turn led to a reduction in right-ventricular function, right-ventricular performance, which decreases pulmonary blood flow. And of course, pulmonary blood flow is exactly the same as your cardiac output, so ultimately that right-ventricular dysfunction led to the cardio-vascular collapse that occurred around 2130." 1. It is then necessary to return to the oral evidence of Dr Barratt, upon which the trial judge placed significant weight. 2. Dr Barratt was cross-examined about the conversation he had with Dr Sparks over the telephone. His evidence was that the conversation took place at about 9.30pm, but it was accepted that the phone call occurred just prior to 9pm. He agreed that the discussion had included the possibility of cardiac compression generating the potential for hypotension with the consequence that critical organs might not be adequately perfused. The discussion had included Dr Sparks' concern about high arterial carbon dioxide and the fact that he had checked that the patient was properly ventilated "but he still could not explain the problem." The cross-examination continued: [41] "Q. So your response was that probably, or maybe, a pulmonary artery was compressed along with possible cardiac compressions, it means his lung was being ventilated but not perfused? A. That is exactly correct. Q. What is ventilated but not perfused mean? A. It means that there is inability to eliminate carbon dioxide from the lung because there's no blood going through the alveolus and all this air is just coming into the lung and can't take the carbon dioxide out so the carbon dioxide is going to build up. Q. And the consequence of that is what? A. A carbon dioxide level of 65 is not a problem physiologically but for that to happen, you have to be pressing on a pulmonary artery in such a significant way that it's going to impede [cardiac] output and organ perfusion. Q. And the consequence of that is what? … If uncorrected? A. Critical end–organ ischemia. … Q. And the consequence of that in a longer term sense if these organs are damaged was what? A. Well, a low [cardiac] output state could damage the brain, the spinal cord, the kidneys, or the liver, for instance, potentially. … Q. Doctor Sparks told you that the various metabolic indicators were critical? A. Yes, yes. Q. Despite, apparently, adequate blood pressure and blood oxygen levels. That was one of his dilemmas, wasn't it? A. Yes, yep. Q. Then in those circumstances, it really wasn't appropriate, was it, to look at the blood pressure and oxygen levels alone when making a decision whether to persist or abandon surgery? A. I agree with that statement." 1. The trial judge's conclusion, based on that evidence was expressed in the following terms: [42] "It is important not to lose sight of the fact that Dr Sparks and Dr Gray were confronted with what was patently a distressing and fraught intraoperative emergency. It is difficult to over-emphasise just how awful it must have been at that time for all concerned. It is clear that Dr Sparks had attempted all of the anaesthetic manoeuvres in his armoury to correct the problem without apparent success. Criticism of these doctors in those circumstances may seem harsh. However, it is not in question that stopping the surgery when no obvious answer to the problems confronting the doctors was presenting itself would have avoided the damage. We know with hindsight that postural adjustment from prone to supine produced immediate resolution of these problems. That was something which in my opinion Dr Sparks and Dr Gray should have foreseen and acted upon. Failure to do so amounted to a want of reasonable care. It was in my view not appropriate to take the risk that something that could not be explained would or might somehow spontaneously resolve or improve. It is no answer to insist that the surgery was lifesaving in circumstances where Mr Hobson's respiratory difficulties at or after 20.30 had deteriorated below his pre-operative condition in ICU." 1. Finally, the judge considered that the absence of spinal cord monitoring "heightened the need to act conservatively and to proceed expeditiously. It told against the appropriateness of taking an expectant approach when the solution to Mr Hobson's difficulties had not emerged or was not understood." 2. So far as Dr Sparks is concerned, and without reference to s 5O of the Civil Liability Act, in my view that conclusion was sound.

Application of s 5O

(a) approach adopted at trial 1. For reasons set out above, the proper course in a case where s 5O has been pleaded and has been the subject of evidence is to determine first the standard of care to be applied, before assessing the alleged negligence against that standard. The trial judge did not take that approach but rather, in accordance with what was understood to be the appropriate course at the time, considered s 5O as a defence to be addressed after findings had been made on the plaintiff's case. That indeed was the manner in which counsel for Dr Sparks dealt with the matter in written submissions at trial. 2. Counsel for Dr Sparks asserted that where there is evidence to demonstrate that the defendant acted in a manner which was widely accepted by peer professional opinion as competent professional practice, that opinion determined the standard of care and the expert evidence was conclusive. [43] Counsel further asserted that the approach adopted by this Court in McKenna should not be followed as it was inconsistent with the reasoning in Dobler. However, if McKenna were to be followed, it was submitted that the conduct of the defendant in exercising judgment as to the time for cessation of the operation constituted a "practice". The submissions simply relied upon the evidence of Dr Forrest as establishing the defence. In oral submissions, there was reference to the reasoning in McKenna, but no further attempt to grapple with the evidential requirements of s 5O. 3. In these circumstances, it is unsurprising that the trial judge dealt with the matter by way of a defence, noting the paucity of evidence in support of it. Having already rejected the views of the defendants' doctors as to whether the conduct of the practitioners was negligent, the judge considered that the defence under s 5O had also effectively been rejected. [44] 4. It is correct to say that the reasoning of the trial judge did not address the submission that Dr Forrest's evidence could not be rejected unless it was shown to be irrational. Nor did it expressly address the proposition that Dr Forrest's opinion was "conclusive" as to the relevant standard of care. Grounds 1 and 2 in Dr Sparks' notice of appeal rely on these matters as demonstrating error. 5. On the appeal, Dr Sparks' written submissions identified the evidence relied on in support of the s 5O test as that of Dr Forrest (called in Dr Sparks' case) and the evidence of Dr Manasiev, called for Dr Gray but who expressed opinions as to the conduct of both Dr Gray and Dr Sparks. It was submitted that the opinions were unchallenged. 6. As Simpson JA explains, the trial did not proceed smoothly. The pleadings left much to be desired as to detail; parties were joined and then removed; the plaintiff's case was recast on more than one occasion, and the evidence of the experts was, inevitably in these circumstances, not always clearly directed to the issues as they finally emerged. The task of the trial judge in these circumstances was fraught with difficulties. Nevertheless, it is apparent that s 5O was relied upon by Dr Sparks and was not correctly disposed of at trial. It is therefore necessary for this Court to address the evidence. 7. Despite the conclusion reached above that the proper approach where s 5O is relied upon is to consider all the evidence in order to reach satisfaction as to the relevant standard of competent professional practice, to adopt such a course on this appeal would be impractical for two reasons, both of which operated at the trial. First, one cannot seek to identify a standard of competent professional practice in the abstract; the standard must relate to the specific ways in which negligence is alleged. Because the pleadings of the plaintiff bore limited resemblance to the case ultimately presented for determination, the plaintiff's case provided a moving target for the defendant. (Although there were grumbles in Dr Sparks' written submissions at trial, no issue of procedural unfairness was raised on appeal.) Secondly, the reasoning of the trial judge followed the structure presented by the parties. It would not be possible to recast that reasoning on appeal to comply with a structure not presented at trial.

(b) expert opinion evidence – anaesthetists 1. The primary evidence relied upon by Dr Sparks was that of Dr Forrest, an expert anaesthetist called by Dr Sparks. In his principal report (the only report which addressed this issue) the final question and answer were as follows: [45] "5. Did Dr. Sparks, in his anaesthetic management of Mr Hobson, act in a manner that was widely accepted in Australia by peer professional opinion as competent profession practice, at the time the service was provided? Yes. Mr Hobson was a high-risk patient who required major emergency surgery on his spine, in the prone position. From the preceding, Dr. Sparks identified the critical issue of the patient's bronchial compression preoperatively. … However, it proved very difficult to effectively ventilate the patient in the prone position, despite the trial of a variety of different ventilation techniques. These difficulties were likely due to the patient's pre-existing pneumonia and bronchial compression, which were significantly aggravated by the use of the prone position for surgery. The patient was appropriately monitored intraoperatively, and the anaesthetic drugs, dosages and fluid administration were also appropriate. The management of the patient's critical deterioration at 21:30h was appropriate, as was the decision to abandon the procedure at that time. The anaesthetic management of Mr. Hobson by Dr. Sparks would therefore have been widely accepted by peer professional opinion in 2009 as competent professional practice." 1. In its terms, this answer constituted an opinion that the relevant steps taken by Dr Sparks involved competent professional practice. However, it did not squarely address what became the critical issue, namely whether the failure to terminate the operation at an earlier point satisfied that test. 2. Of course, the answer to question 5 should not be read in isolation. Question 2 invited Dr Forrest to "review the blood gas readings, the blood pressure results and the tidal flow measurements" and express an opinion as to the most likely cause of the collapse at 9.35pm. Dr Forrest answered that question in the following manner: [46] "In my opinion, the cause of Mr. Hobson's intraoperative collapse was acute right ventricular failure (RVF). This would account for the high central venous pressure, low oxygen saturation and low blood pressure that occurred at about 21:30h on 17 November. It would also account for the large difference in the carbon dioxide level measured in the patient's blood and his expired breath ('end-tidal carbon dioxide') prior to that time, the congested ('purple') appearance of his head that was observed when he was turned from prone to supine and the echocardiography findings at that time ('empty LV… RA full'). Mr. Hobson's probably developed acute RVF because of predisposing factors and because of the use of the prone position for his surgery. The predisposing factors that would have contributed to acute RVF were his spinal deformity, which caused restrictive lung function and left lung collapse / infection due to bronchial compression. These factors would have caused the pulmonary arteries to constrict and thereby increased pulmonary vascular resistance (PVR). An increase in PVR causes the RV to dilate and may eventually decrease its capacity to pump blood (cardiac output). When Mr. Hobson was turned prone, it proved very difficult to ventilate him effectively, despite confirmation of the DLT position and despite the use of a variety of different ventilation techniques. As soon as he was turned supine again, ventilation became much easier and his oxygenation, blood pressure and carbon dioxide levels rapidly normalized. The use of the prone position probably compromised his ventilation by increasing compression of the left main stem bronchus by his spine, due to the effects of gravity. His spine may also have been compressing pulmonary arteries and veins, which would also increase PVR and decrease cardiac output. Because of the difficulties in ventilation, the carbon dioxide level increased in his blood. This would also have significantly increased PVR, because raised carbon dioxide levels cause the pulmonary arteries to constrict. The combination of increased PVR and decreased cardiac output cause the blood supply to the RV itself to fall. When the blood supply to the RV falls below a critical level, acute, severe RVF can occur. However, it is not possible to accurately predict in an individual patient if, or when this will occur." 1. The next question asked whether it was appropriate and reasonable for Dr Sparks to direct that the surgery cease at about 9.30pm. He said that it was and continued: [47] "Taken in isolation, a fall in blood pressure to 95mmHg (even from a high baseline value) would not be sufficient reason for abandoning a surgical procedure. However at that time (about 21:30h), Mr. Hobson also had rapidly falling oxygen saturations (to less than 80%), a high CVP and severe respiratory and metabolic derangement. Hence this blood pressure signalled the onset of critical haemodynamic deterioration, which would likely have rapidly progressed to refractory cardiac arrest if surgery had not been abandoned at that time and he was not turned supine. It was therefore appropriate and reasonable for Dr. Sparks to request that surgery be abandoned at that time." 1. Finally, Dr Forrest was asked to express his own opinion as to the standard of anaesthetic management during surgery. In concluding that the standard was reasonable, he stated: "Mr. Hobson was a high-risk patient who required major emergency surgery at that time. He posed a very unusual and difficult anaesthetic challenge due to the significant compression of his left main bronchus by his spine and due to the requirement for prone positioning during surgery. … The main clinical dilemma in this case was whether surgery should have been allowed to continue given the difficulties in ventilating the patient that were encountered before the severe deterioration that occurred at 21:30h. As noted above, he patient had been difficult to ventilate prior to this time due to compression of his left main bronchus, which was exacerbated in the prone position. However, given that the patient's surgery was considered to be sufficiently urgent that it needed to be performed out-of-hours, and given also that his lung infection would not have been expected to resolve until the compression of his left main bronchus was relieved by surgery, it was reasonable to continue the anaesthetic at that time." 1. As with the answer to question 5, in relation to widely accepted peer professional opinion, Dr Forrest's statement as to his own view deals with the question of earlier termination only indirectly. The final conclusion "it was reasonable to continue the anaesthetic at that time" is not precise as to the time in question. Secondly, unlike Dr Sparks, Dr Forrest, in explaining Mr Hobson's situation, placed weight upon the raised carbon dioxide levels and their effect in causing constriction of the pulmonary arteries and therefore pulmonary vascular resistance, leading to decreased cardiac output and ultimately right ventricular failure. It was clear at some point that the only answer to those problems was to cease surgery and return the patient to a supine position, as eventually happened. 2. The submission that Dr Forrest's views were not challenged was only partly true. In the course of his joint evidence with Dr Westbrook, senior counsel for the plaintiff obtained Dr Forrest's agreement that there was continuous deterioration of the plaintiff's metabolic state, and that acidosis was a harbinger of ongoing problems which could, unresolved, have proved fatal. The cross-examination ended with the following exchange: [48] "MENZIES: … What I'm suggesting to you, for example, that if at any of those times before 2051, a decision was made to stop the surgery at that time, it's not as if the consequence was going to be the patient was going to die in front of you, is it? WITNESS FORREST: What the consequence would have been – and the expectation of the doctors looking after the patient at that time would have been – that because they hadn't corrected his underlying bronchial compression, that he would continue to have ongoing severe respiratory failure, which would ultimately be – would ultimately lead to his demise because the underlying cause had not been addressed. MENZIES: So the proposition remains the same, doesn't it? That the semi-emergen[cy] situation as you describe it – but I'm happy with that – continued unchanged. In other words, at any time before 2125 or 2130 when the surgery was stopped, it could have been stopped with no further harm to the patient than he was already suffering. That's right isn't it? WITNESS FORREST: Yes, well, that's right. But as I've already said, the reason why the surgery was done in the first place at that time was because it was felt that ... (not transcribable)…would not be improved if his surgery had not gone ahead. So expectation would have been that he would have died at some point post-operatively in intensive care from… (not transcribable)… respiratory failure." 1. Neither the questions nor the answers given by the witness were entirely clear. The question to be answered by the Court is whether the evidence of Dr Forrest, taken as a whole, established the proposition that it was widely accepted peer professional opinion that it would be competent professional practice to continue the administration of anaesthetic for the purpose of surgery in all the circumstances. That required taking into account the need for the corrective surgery, and the deterioration in the patient's condition as at about 9pm, given the expectation that it would be relieved by ceasing the operation and returning the patient to the supine position. To the extent that the evidence did address that proposition, it is by no means clear that Dr Forrest expressed a clear view about it. 2. Dr Sparks sought to obtain further assistance as to the relevant standard of competent professional practice in the evidence of Dr Manasiev. Dr Manasiev is a consultant anaesthetist and was called on behalf of Dr Gray. The doctor was asked a number of questions; question 2 was whether Dr Gray should have halted or advised "the halting of the surgery following the earlier episodes of hypoxia and hypotension … and related complications reported in the anaesthetic record between approximately 19:10 and 21:20." [49] After dealing with two earlier events which are no longer significant, Dr Manasiev dealt with "a transient period of desaturation and relative hypotension" at 20.35. The event occurred at the time of placement of a pedicle screw in the patient's spine. He identified three reasons for not halting the operation at that time. First, the cause was transient and, secondly, the blood pressure and saturation returned to normal values once the pressure was relieved. He continued: [50] "Third, the decision was balanced against the apparent necessity of the operation as a potential lifesaving technique. As such, it was not warranted by Dr Sparks or Dr Gray to halt the surgery at this time and would be considered widely accepted in Australia by peer professional opinion as competent medical practice to continue the surgery." 1. After dealing with the appropriateness of halting the surgery at 21.20, Dr Manasiev noted that "the management of the ventilatory and cardiovascular parameters are primarily the responsibility of the anaesthetist." [51] He then repeated, in relation to Dr Sparks, his opinion as to competent medical practice as at the times identified in question 2. 2. Dr Manasiev did not participate in the joint conclave of anaesthetists with Drs Westbrook and Forrest. However, he gave oral evidence at the trial. In the course of cross-examination he gave the following evidence: [52] "Q. What are the factors, you say, that would inform competent professional practice, with respect to anaesthetists and the continuance or otherwise of a surgery? A. Well, it's the whole gambit of all the hemodynamic parameters that you're looking at within a patient. Predominantly, the blood pressure and saturation, which are telling you how the organs are being perfused, but as well as that, all the attempts that are made, in this case, to improve ventilation: whether they are successful or non-successful, the response of all the blood gas analysis. It's a complicated gambit of numbers and figures that you're looking at. Q. You certainly, do I understand it then, wouldn't limit yourself to the – in a manner which excluded all the other parameters in the blood gases? A. No, you wouldn't exclude all the parameters, no -- Q. Because that would not be consistent with competent professional practice, in circumstances such as this in Australia, in 2009, would it? A. You wouldn't exclude, but you would give different parameters different weights upon the patient's stability." 1. In his original report, Dr Manasiev did not squarely address the effect on his opinion of the evidence accepted by Dr Westbrook and Dr Forrest of the plaintiff's continuously deteriorating metabolic state which was likely to lead to a cardiovascular collapse, if not remedied. Further, the evidence in the course of the trial progressed beyond the parameters put to Dr Manasiev for the purposes of his report. The question was not whether the events around 8.30pm should have led to the termination of the operation but whether the events around 9pm should have led to termination. No evidence was led from Dr Manasiev in relation to these further considerations. 2. In summary, the evidence relied upon by Dr Sparks fell short of establishing a standard, widely accepted in Australia, of competent professional practice. A bald statement by a practitioner, however well qualified, without reference to the specific factors giving rise to a claim of negligence may well not persuade the court that there is a relevant standard identified in the evidence. Further, a bald claim that the practice is "widely accepted" as falling within the scope of competent professional practice may not be accepted by the court as evidence of that fact. To persuade the court that the terms of the section have been satisfied one would generally expect evidence which stated the basis of the standard. Further, the evidence is more likely to be persuasive if it seeks to grapple with possible conflicting views in a reasoned manner. 3. That is not to say that any of the evidence was "irrational". Rather, the test of irrationality applies to the opinion as to competent professional practice. The Court must always be satisfied as to two antecedent questions, namely that the opinion addresses the conduct as found at the trial and that the evidence supports the view that the expressed opinion was, at the time of the conduct, "widely accepted in Australia". 4. In the result, the erroneous approach to the terms of s 5O was not material to the outcome. It follows that Dr Sparks' appeal should be rejected.

Inherent risk – s 5I 1. Adopting the reasoning of Leeming JA in Paul v Cooke, the trial judge rejected the submission that Mr Hobson's injury was the result of an inherent risk which could not have been avoided by the exercise of reasonable care and skill. He accepted that "Mr Hobson was always going to be vulnerable to ischemia during the second stage of the surgery due to the first stage surgery ligation of the segmental spinal arteries that necessarily reduced blood supply to the spinal cord." [53] He repeated that aspect of his medical condition, amongst others, which exposed him to a "pre-surgical anatomical vulnerability to spinal cord stroke and the effects of hypotension." [54] He reasoned that, because the risk could have been avoided by the exercise of reasonable care and skill, it was not an "inherent risk" within the meaning of s 5I(2). 2. On the appeal, counsel for Dr Sparks repeated the submissions which had not found favour at the trial. The submissions ran into one of two difficulties; either they adopted a colloquial meaning of "inherent risk" which does not conform to the specific statutory definition, or they assumed a favourable answer with respect to negligence and causation, which would, of course, render reliance on s 5I otiose. As noted above, the circumstances in which s 5I will provide a valuable defence are likely to be few and far between. This case is not one of them. It is clear that the harm might not have occurred if the operation had terminated at an earlier point in time. It certainly cannot be said that the harm "could not" have materialised through exercise of reasonable care and skill. Furthermore, the issue in the case was whether the harm eventuated as a result of the failure to exercise reasonable care and skill. That question cannot be avoided by relying on s 5I.

Conclusion 1. As the trial judge fairly recognised, Dr Sparks was faced with a difficult intraoperative choice. However, it was not one which required an instantaneous decision, nor one which required further information or advice. The patient's metabolic decline was continuing despite Dr Sparks having taken every available step to alleviate the condition whilst the operation proceeded. Whilst the operation continued, the patient was heading for cardiovascular failure. The operation was expected to last for some four hours; at 9pm the operation was only half completed, on that timescale. (The orthopaedic experts stated that it had 2-4 hours to go. [55] ) The decision to allow it to continue for 30 minutes after Dr Sparks had sought help from two experienced anaesthetists, without success, involved more than an erroneous clinical judgment; the trial judge was correct to find a breach of duty of care.

Dr Gray 1. The responsibility of Dr Gray as the principal surgeon is to be determined on the expert evidence regarding medical practice in Australia. Although the Court was referred to authorities dealing with the role of the surgeon, the defence under s 5O is not established according to a legal standard as such, but rather by widely accepted peer professional opinion. Case-law will not assist in identifying the role of each of the medical practitioners in the operating theatre; that needed to be determined on the facts of the case as they appeared in the evidence; no question of legal principle was raised. 2. In passages which have already been considered, the trial judge treated the liability of Dr Gray and Dr Sparks as necessarily to be assessed on the same basis. There were certainly reasons why that might have been thought appropriate. First, because Dr Gray was in charge of the operation, and would be the person primarily responsible for monitoring its progress, one might expect that he would be kept informed of any difficulties with anaesthesia including ventilation of the lungs and levels of blood gases. Secondly, he accepted in his evidence (and particularly his affidavit of 7 November 2016) that he was being informed by Dr Lagopoulos of the findings based on the spinal cord monitoring, up until the monitoring was terminated. His evidence treated the decision-making as jointly undertaken: [56] "21. The deterioration in the plaintiff's respiratory function in ICU prior to surgery had necessitated the surgery being brought forward. Respiratory failure could have resulted in death. The decision to bring forward the surgery was to avoid the risk of fatality. 22. In view of this risk, the lack of spinal cord monitoring became secondary and Dr Cree and I decided to continue with the surgery. We made a collective decision that it would be appropriate given the circumstances of it being a life-saving procedure to continue with the surgery. 23. The plaintiff, shortly before the surgery was stopped, underwent a rapid deterioration, one aspect of which related to a reduction in his level of oxygenation. 24. Dr Sparks informed those present of difficulties encountered by him including the ongoing reduction in oxygenation, hypotension, a decrease in end-tidal CO2 and an increase in PaCO2. He said words to the effect 'I'm having problems with ventilating …'. … 25. Dr Cree said words to the effect 'Should we stop'. Dr Sparks indicated that the surgery could continue. Dr Sparks said [words] to the effect of 'no, keep going, I'll let you know'. Dr Sparks then shortly afterwards indicated that it would be necessary to cease the surgery. Dr Sparks said words to the effect 'I think we need to stop'. There was a collective discussion and decision to cease the surgery." 1. In this evidence, and in his oral evidence, Dr Gray spoke in terms of a consultative team working together. 2. There were countervailing considerations. First, as Macfarlan JA explains, the evidence did not demonstrate knowledge on Dr Gray's part which would suggest that he had full understanding of the difficulties which Dr Sparks was facing. Secondly, Dr Sparks was cross-examined by counsel for Dr Lagopoulos (whilst he was still a defendant): [57] "Q. The decision to stop the surgery at about 21.30 on 17 November 2009 was made by the process of discussion amongst the members of the surgical and the anaesthetic team. Isn't that correct? A. Yes, but I think it was really my decision. Q. Thank you. However, there was consultation between the two? A. There was no disagreement when I told them what I thought." 1. It was not suggested to Dr Sparks that he had at particular times conveyed to Dr Gray his specific concerns, or entered into a consultation as to how long the operation was likely to take. 2. Thirdly, there was the evidence of Dr Manasiev to which reference has been made in a different context: [58] "It is important to note that the management of the ventilatory and cardiovascular parameters are primarily the responsibility of the anaesthetist. The anaesthetist would be the first to comment on difficulties in achieving adequate ventilation and perfusion of the vital organs and as such direct the surgeon if the surgery would need to be halted to effectively resuscitate the patient. It would not be the responsibility of the surgeon to halt the surgery on the basis of haemodynamic or respiratory difficulties unless there was a question of the management of those difficulties by the anaesthetist." 1. That passage was raised with Dr Manasiev by counsel for the plaintiff in cross-examination: [59] "Q. So that if the anaesthetist was reporting difficulties, then it would be incumbent upon the surgeon, wouldn't it, obviously depending on what has been told, to make a decision to halt the surgery? A. Yes, a communication process between the anaesthetist and the surgeon together. Q. Of course, the ultimate decision to stop must be in the hands of the surgeon, because the anaesthetist is hardly in a position to say, 'stop, I'm out of here,' is he? A. Yeah, can't physically restrain the surgeon from operating, but, yeah ultimately, the surgeon would decide if and when he stops." 1. According to Dr Gray, Dr Cree's inquiry as to whether the surgery should stop, with the response from Dr Sparks saying they could proceed, came only minutes before Dr Sparks told them to stop. Dr Cree's question, as Dr Gray recalled it, was in response to a remark by Dr Sparks, "I'm having problems with ventilating …". It can reasonably be inferred that no other information suggesting significant difficulties had been conveyed by Dr Sparks after the spinal cord monitoring terminated. Dr Gray also gave evidence that he was not aware of Dr Sparks leaving the operating table to make telephone calls. 2. Based on this evidence, I agree with Macfarlan JA that the case in negligence against Dr Gray should have been dismissed. 3. Given this conclusion, it is not necessary to address the other grounds of appeal raised by Dr Gray.

Damages 1. Dr Gray raised three specific challenges to the assessment of damages undertaken by the trial judge. The same challenges were raised in Dr Sparks' appeal, but Dr Sparks made no specific submissions in relation to these issues, merely adopting the submissions made on behalf of Dr Gray. Although Dr Gray's appeal has been upheld and the issues do not arise in his case, it is necessary to deal with the challenges thus adopted by Dr Sparks. 2. I agree that each of the challenges should be rejected, for the reasons given by Macfarlan JA.

Conclusion 1. For these reasons I agree with the orders proposed by Macfarlan JA. 2. MACFARLAN JA: Mr Brendan Hobson, the respondent, was born in 1985. He suffers from Noonan Syndrome, a genetic disorder that prevents normal development in various parts of the body. As a result of the disorder, Mr Hobson's breast bone was too close to his spine. This restricted his ability to fill his lungs with air, and hence to breathe. Without surgical intervention to create more space in his chest cavity by straightening his spine, his prognosis was grave. 3. Surgery to correct this problem was designed to take place in two stages. The first operation was successfully undertaken on 13 November 2009. The second, which occurred on 17 November 2009, had to be terminated before its intended conclusion. As a result of that operation, Mr Hobson became a paraplegic. 4. In the proceedings now under appeal, Mr Hobson initially claimed damages from the hospital where the operation took place and from a number of members of the surgical team. Ultimately, his claim proceeded only against the principal surgeon, Dr Randolph Gray, and the principal anaesthetist, Dr Christopher Sparks. Dr Gray is an experienced specialist orthopaedic/spine surgeon and Dr Sparks is an experienced specialist anaesthesiologist. 5. After an 11 day hearing before Harrison J in the Common Law Division of the Supreme Court, his Honour found that Drs Gray and Sparks had breached the duties of care that they owed to Mr Hobson and were liable in negligence for damages in the amount of $3,828,075. 6. The basis of the decision against both doctors was that, in light of adverse blood gas readings for carbon dioxide obtained in the course of the operation, they should have caused the operation to be terminated earlier than occurred. If the operation had been so terminated, Mr Hobson would not have had a significant cardio-vascular collapse at about 21:30 on 17 November, his spine would not have been damaged and he would not have become a paraplegic. 7. His Honour rejected a number of other particulars of negligence, including that the operation should not have proceeded at all on 17 November. 8. Drs Gray and Sparks each appeal against the primary judge's decision on liability and, in three limited respects, against his Honour's assessment of damages. As to the latter, they contend that his Honour erred in the allowances that he made for past and future domestic care, and for motor vehicle expenses. Mr Hobson has not filed a cross appeal or notice of contention. 9. As well as contending that the primary judge erred in finding that they acted negligently, the appellants rely, as they did at first instance, on sections 5 I and 5 O of the Civil Liability Act 2002 (NSW). These sections are in the following terms: "5I NO LIABILITY FOR MATERIALISATION OF INHERENT RISK (1) A person is not liable in negligence for harm suffered by another person as a result of the materialisation of an inherent risk. (2) An inherent risk is a risk of something occurring that cannot be avoided by the exercise of reasonable care and skill. (3) This section does not operate to exclude liability in connection with a duty to warn of a risk. 5O STANDARD OF CARE FOR PROFESSIONALS (1) A person practising a profession ("a professional") does not incur a liability in negligence arising from the provision of a professional service if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice. (2) However, peer professional opinion cannot be relied on for the purposes of this section if the court considers that the opinion is irrational. (3) The fact that there are differing peer professional opinions widely accepted in Australia concerning a matter does not prevent any one or more (or all) of those opinions being relied on for the purposes of this section. (4) Peer professional opinion does not have to be universally accepted to be considered widely accepted." 1. Before turning to the evidence adduced at first instance which is relevant to the issues on appeal, it is convenient to give a brief description of the doctors involved in the events in question and of the medical experts, and to summarise the issues that arose in relation to the second operation. 2. Dr Gray was the principal surgeon. He was assisted by Dr Cree and Dr Lyons. Dr Sparks was the principal anaesthetist. He was assisted by Dr Wang. Dr Lagopoulos, a specialist neurophysiologist, was a part of the surgical team but was not present between 20:30 and 21:30 when the events of concern on the appeal occurred. Dr Stephen Barratt, a specialist anaesthetist, was not present at the operation but spoke to Dr Sparks at about 20:50 when Dr Sparks called him for advice. At about the same time, Dr Sparks also called Dr Marshman, a cardiothoracic surgeon. Dr Marshman did not give evidence. 3. At the trial, Mr Hobson tendered expert reports by Dr John Westbrook (a specialist anaesthetist), Dr James Wilson-Macdonald and Dr Michael Johnson (the latter two being specialist orthopaedic surgeons). The appellants called expert anaesthetic evidence from Dr Paul Forrest and Dr Bojidar Manasiev, and expert orthopaedic evidence from Dr Geoff Askin. 4. In their written submissions, Dr Sparks' counsel described the physiological issues that arose in relation to the second operation as follows: "24. The treating and medico legal expert evidence demonstrated these things: a. The second stage surgery required Mr Hobson to be placed faced down (prone) on the operating table, allowing the surgeons to access the spine posteriorly and perform the spinal fusion. b. The fusion required the placement of pedicle screws. The actions of the orthopaedic surgeon emplacing the pedicle screws can put downward pressure on the patient's spine, and with it, the risk of cardiac compression. c. With Mr Hobson being in the prone position, the effects of gravity may have unavoidably caused his spine to compress the left main bronchus and the pulmonary arteries and veins. d. Compression of the pulmonary arteries and veins can increase pulmonary vascular resistance, which decreases cardiac output. As a result, carbon dioxide in the blood (PCO2) increases, which in turn causes the pulmonary arteries to constrict. The combination causes blood supply to the right ventricle to fall, leading to reduced cardiac output and if it falls to a critical level, right ventricular failure (cardiac collapse) occurs. e. An elevated PCO2 causes the blood's pH to drop, (known as respiratory acidosis) which, alone or together with a decreased base excess and an elevated lactate, are markers indicative of metabolic acidosis (a build-up of metabolic acids in the body)" (citations omitted). 1. To this should be added that the cardiac compression indicated by high carbon dioxide readings can result in inadequate supply of oxygenated blood to the body's organs including, as occurred in Mr Hobson's case, to the spinal cord.

THE EVIDENCE AT THE TRIAL

Dr Christopher Sparks 1. In his affidavit of 11 November 2015, Dr Sparks said that he understood that the close proximity of Mr Hobson's vertebral column to his sternum was displacing his heart into his left thorax. Dr Sparks' understanding was that without surgery this condition could be fatal, and that it followed that surgical intervention was required to save Mr Hobson's life. Dr Sparks understood that prior to the operation on 17 November 2009 the intensive care unit ("ICU") was having difficulty ventilating Mr Hobson because of compression of his left main bronchus, and that Mr Hobson was developing pneumonia. 2. When Mr Hobson was turned to the prone (that is, face down) position at the commencement of the operation on 17 November, Dr Sparks asked the surgeons if they could "minimise downward force on Mr Hobson's spine during the operation as it could cause cardiovascular compression". Dr Sparks recognised the possibility of increased compression on Mr Hobson's pulmonary artery whilst in the prone position. 3. Dr Sparks continued: "31 The medical records show the operation commenced at about 19:30 to 19:40 hours. 32 The blood gas readings at 19:13 hours were: P02243 (90 to 95 normal parameters) and PC02 65 (35 to 40 normal parameters). A PC02 reading of 65 was outside of normal parameters and in normal circumstances I would not anaesthetise such a patient but the emergency nature of the situation meant I needed to accommodate the PC02 level and did so by increasing ventilation in response. I assumed the PC02 at 65 was a result of low minute volume, which is the reason why the ventilation was increased. I assumed the high reading of a P02 at 243 was a result of Mr Hobson's left lung being oxygenated effectively for the first time in 4 days. 33 By around 20:30 hours the arterial blood CO2 level had risen from 64.7 mmHg to 70.5mmHg. I could not detect any mechanical obstruction to ventilation but nevertheless I felt compelled to give muscle relaxant, Vecuronium. I informed the surgeons of this course of action. 34 Vecuronium was administered at around 20:30 hours in response to the rising carbon dioxide level. It was given to allow us to attempt to improve ventilation. The O2 partial pressure remained high and the trend systolic blood pressure was normal to high. Because it was emergency surgery I had resolved in my mind that while the oxygenation and blood pressure were normal to high it was appropriate for the surgery to continue. 35 The arterial carbon dioxide levels continued to be elevated and I tried everything I could think of to identify the cause of the problem. I checked for mechanical problems with the ventilation. I increased the tidal volume, I undertook hand ventilation and I checked the position of the tube with the bronchoscope several times, but there was no mechanical problem with the double lumen tube or the breathing circuit. 36 I considered a pneumothorax and breath stacking in the left thorax. I tried to disconnect the left lung from ventilation and leave it open to air, but the blood gas results stayed much the same. The partial pressure oxygen (PO2) remained high. 37 The arterial carbon dioxide continued to be elevated and the expired waveform diminished. I tried hand ventilation and I got down on my knees on numerous occasions to check the tube with the bronchoscope again, but it was always in the correct position. I was comfortable that the double lumen tube was working properly. 38 Having excluded these reasons for the problem, I formed the opinion that the likely cause was cardiac and not the ventilation. I formed this opinion even though the systolic blood pressure was stable at about 150 systolic for most of the time. Each arterial line in the left and right hands measured the blood pressure continuously and recorded the same result. 39 I was conscious of Mr Hobson's history of previous ASD repair and pulmonary valvectomy in 1988; and a prior trans-thoracic echo showing raised pulmonary artery pressure. In addition there was the thoracic vertebral body compressing the Left Atrium all of which indicated that the patient's right ventricle had a high workload. I considered the use of cardiac inotrope but rejected it. With a typical systolic pressure of 140 to 150 during most of the surgery and obstruction to the right ventricle caused by bone I felt that inotropes would only precipitate Right Ventricular Failure. In short I thought that inotropes were unlikely to assist or help the patient, rather they were more likely to harm him. 40 By about 20:50 hours, I telephoned Dr Barratt and Dr Marshmann (sic), cardiothoracic surgeon, to discuss the circumstances, specifically the patient's low exhaled C02 even though the blood pressure was high to normal and normal ventilation. Neither specialist could recommend anything that I had not already considered. In my telephone conversation with Dr Barratt, he said words to the effect: 'it must be due to 'dead space' and not a problem with ventilation'. Dr Marshman had nothing further to add. 41 By about 21:25 hours, 2 hours into the procedure, the exhaled carbon dioxide expired waveform had diminished, which most likely meant that not enough blood was reaching the lungs. The CVP was 37 and I was concerned that the right ventricle was failing. I raised my concern with Drs Gray and Cree with words to the effect: 'hurry up as the patient's condition is deteriorating'. They responded by agreeing to operate faster in order to complete the operation as quickly as possible. 42 However, over the following minutes I became very concerned that Mr Hobson was about to suffer a cardiac arrest as his blood pressure dropped from the previous level of 150. I administered Adrenaline and directed Dr Gray to stop the procedure immediately. Dr Gray closed up the wound as quickly as possible without completing the spine stabilisation, and Mr Hobson was turned to a supine position on the bed. 43 Once he was turned to a supine position, Mr Hobson's head was noted to be a purple colour, although within a relatively short space of time his carbon dioxide, blood pressure and CVP levels all returned to normal as did his colour without any other intervention." 1. In relation to the administration of vecuronium (a muscle relaxant) at 20:30, Dr Sparks gave the following answer to an interrogatory: "I formed the opinion that the patient's PaCO2 was very serious and believed that if a muscle relaxant was administered, it may bring the patient's PaCO2 down. As it was an emergency procedure and the consequence of the surgery not proceeding was the likely death of the patient, I felt obliged to try administering the muscle relaxant to reduce the PaCO2." 1. In relation to the termination of the operation, Dr Sparks stated: "Dr Wang and I agreed that while the arterial blood gas oxygen was normal to high and the blood pressure was normal to high it was reasonable for the surgeons to try and complete the operation. By around 21:28hrs however, it was clear to us that it was not possible for the operation to complete by those two criteria so I immediately told the surgeons to stop operating. They agreed immediately." 1. Dr Sparks gave the following further evidence in the course of his cross-examination. 2. Dr Sparks said that at around 20:30, in response to Mr Hobson's raised carbon dioxide levels, he decided that vecuronium would be administered. He gave evidence that there were two ways in which the vecuronium might have reduced Mr Hobson's carbon dioxide reading to a more acceptable level. First, "it decreases the oxygen consumption and carbon dioxide production on muscles, and secondly, [it was administered] in the hope that it would improve his ventilation which is the normal cause of a raised carbon dioxide impaired ventilation, total volume minute volume". 3. Dr Sparks said that during the operation Mr Hobson was being effectively ventilated, and therefore his carbon dioxide level should have been normal. Instead it was high, indicating that something was wrong. Dr Sparks gave evidence that there are three causes of an elevated carbon dioxide level. One is a problem in ventilation, another is increased carbon dioxide production (in this case, possibly as a result of a slight fever which Mr Hobson had), and the third is a cardiac problem. By a cardiac problem, Dr Sparks was referring to "dead space" in one of Mr Hobson's lungs. This meant that "part of the lungs was being effectively ventilated but there was no blood being delivered to that part of the lungs. Therefore, the carbon dioxide from that blood was not being removed from the circulation and delivered to the breathing tube and exhaled outside the patient. It was going around for another lap". 4. Dr Sparks agreed that the blood gas samples taken at 20:08 and 21:00 indicated a very high carbon dioxide level and significant respiratory acidosis (that is, low bicarbonate concentration), and that "there was early evidence of an increasing lactate level suggesting inadequate organ perfusion". He agreed that he had no clear means of reversing what he described as "a definite metabolic and respiratory acidosis" (see [24(e)] quoted in [118] above), and that there was a deteriorating trend in Mr Hobson's condition. He gave evidence that at the time he called Dr Barratt he was concerned about Mr Hobson's high arterial carbon dioxide level, which was "one and a half times normal". 5. Dr Sparks agreed that the respiratory difficulty caused by compression was certain to be worse in the prone position. He said that he became conscious of the problem about which he called Drs Barratt and Marshman at least 40 minutes before he made the calls, that is from the moment that Mr Hobson was turned into the prone position. He also stated that Mr Hobson "had a squashed heart" from when he was turned prone. 6. Dr Sparks said that he understood that Mr Hobson "needed life-saving surgery within 24 hours of when we were together discussing the patient at 2.00pm" (on 17 November), and that he believed that "the cardiac compression would always be there, unless we corrected it, and that therefore to make him better, we had to make him worse in the short [term]". He said that he "felt compelled to go on while the oxygen and the blood pressure were normal to high", and made a decision that he would continue with the operation while Mr Hobson's systolic blood pressure and oxygen levels were within this range. He said that with the "other factors you can survive and get through and still have a normal outcome," but that "those are the two things that you can't - if they become abnormal, the oxygen or the low blood pressure, the patient will definitely suffer permanent damage. … They were the two I decided would be my criteria for stopping the operation". He said that until Mr Hobson's blood pressure and oxygen dropped (at around 21:25) the "risk of not going ahead exceeded the risk of going ahead". 7. Dr Sparks agreed that after the operation, Mr Hobson continued to be treated in the ICU and that, as a result of that treatment, a few weeks later Mr Hobson was in a position "where his respiratory condition was such that surgery proceeded without any of the difficulties so far as the administration of anaesthesia was concerned, which existed at the time of the second surgery [on 17 November 2009]". Dr Sparks then answered the following question in the affirmative: "So doesn't it follow ineluctably that rather than one proceeding with this emergency surgery, had a decision been made not to proceed but to continue to treat him in ICU with all of those measures, he would have (a) survived, and (b) improved to the point where he could be operated upon without the risk of the catastrophic events that occurred on 17 November?"

Dr Randolph Gray 1. Dr Gray described Mr Hobson's respiratory difficulties and the circumstances in which the 17 November operation was terminated as follows: "46 The patient, due to respiratory difficulties, had to be paralysed through the use of a muscle paralysing agent in order to be ventilated. Vecuronium was used by the Anaesthetic team to paralyse the patient. With the muscle paralysis, the patient's motor evoked potentials had become non-monitorable. Therefore further spinal monitoring was discontinued as the patient needed to be paralysed for the rest of the procedure to aid ventilation. 47 Dr Sparkes (sic) informed those present of difficulties encountered by him including the ongoing reduction in oxygenation, hypotension, a decrease in end-tidal CO2 and an increase in PaCO2. He said words to the effect 'I'm having problems with ventilating …'. There was a collection of anaesthetic issues including hypoxia, hypotension, decreasing end-tidal CO2 and increasing PaCO2. Dr Cree said words to the effect 'Should we stop'. Dr Sparkes indicated that the surgery could continue. Dr Sparkes said words to the effect of 'no, keep going, I'll let you know'. Dr Sparkes then shortly afterwards indicated that it would be necessary to cease the surgery. Dr Sparkes said words to the effect 'I think we need to stop'. There was a collective discussion and decision to cease the surgery. 48 The surgery was abandoned and the wound was rapidly closed. The patient was repositioned to the supine position. There was significant hypertensive down time." 1. Dr Gray gave the following presently relevant answers to interrogatories: "31 Did the plaintiff suffer any episodes of hypoxia during the surgery? Answer: The plaintiff, shortly before the surgery was stopped, underwent a rapid deterioration, one aspect of which related to a reduction in his level of oxygenation. I do not know whether this can be categorised as an 'episode of hypoxia'. Reference can be made to the detailed anaesthetic records. … c) If so, what did you do or say in response, if anything? Answer: In the context to the answer to interrogatory 31(d) below Dr Cree and I continued to operate until Dr Sparks indicated that it would be necessary to stop the surgery. d) If so, what did anyone else do or say in response, if anything? [Dr Gray's answer to this interrogatory was in the same terms as [47] of his statement quoted in [123] above. He added the following] I am not aware of the precise time or times at which various statements were made concerning difficulties with maintaining ventilation of the plaintiff and whether to cease the surgery." 1. In cross-examination, Dr Gray explained the circumstances of the administration of vecuronium at 20:30 as follows: "My recollection is that when Dr Sparks was having difficulty with the ventilation of the patient, he did inform the surgical team that he may need to administer vecuronium in order to continue ventilating the patient. A collective decision or agreement was made at that point in time that that was necessary in order to improve ventilation of the patient and it was inevitable that as a result of that, we would lose monitoring." 1. Dr Gray then agreed to the proposition that whilst the operation was continuing there could have been conversations between those present that he "may not necessarily be listening to or hearing". He said that he was not aware that during the operation, Dr Sparks left his position at the head of the patient and went to make a telephone call. 2. Dr Gray agreed that the first surgery (on 13 November) had had the effect of reducing the blood supply to the spinal column and that it would be necessary for him "to be even more vigilant [in the 17 November operation] than he would otherwise be in [the] circumstance[s] because the blood supply had been compromised". 3. Dr Gray described the information he received during the 17 November surgery as follows: "So the feedback that Dr Cree and I [were] getting during the surgery is that the patient's blood pressure and oxygenation was normal and was adequate. And those were the two single most important factors when it comes to cord perfusion and a cord injury until that very last minute when there was a catastrophic arrest or drop in blood pressure and oxygenation. So up to such time, the two parameters that we were concerned or was giving attention to was fine (sic)." 1. He agreed that the spinal cord can be damaged as a consequence of low cardiac output. 2. Dr Gray gave the following evidence concerning his role and that of the anaesthetist: "Q. Doctor, at 20:08 there were very high carbon dioxide levels despite the attempts at pulmonary ventilation with a double lumen tube, and this was causing a significant respiratory acidosis, wasn't it? A. At the time I was concentrating on my surgery and I was not entirely informed and aware of the, the nuances and details of these changes. Q. Had you been aware, do I take it, that at 21.08 there was a significant respiratory acidosis occurring, then you would be very concerned, wouldn't you, that there was likely to be damage to the spinal cord? A. Acidosis per se is not a parameter by itself to – known to cause spinal cord injury. It's a reflection of another process that's happening at the time-- Q. Be that-- A. --and-- Q. --as it may, it is a sign, isn't it, that there is a significant risk at that time of spinal cord injury? A. I don't agree that the acidosis per se is a cause of spinal cord injury and I was not in a position at the time whilst doing the surgery to analyse the spirometers and make anything out of it because I was performing the surgery and doing it as quickly as I can to minimise operating time and-- Q. I understand that. A. --I rely-- Q. Sorry, go on. A. --on my anaesthetic colleagues to inform me of the summary of these events. Q. Had you been told at that time that there was a significant respiratory acidosis then you would have to consider then, wouldn't you, stopping the surgery? A. I would put the question to the anaesthetist. I wouldn't, I wouldn't make decisions based on medical parameters, whether to stop the surgery or not, I would be taking the advice of my anaesthetic colleagues. Q. Doctor, the effect of the acidosis is it could lead to cardiac failure. That's right, isn't it? A. Yes. Q. That then could well cause spinal damage. That's right, isn't it? A. Yes. Q. So could I suggest to you this – leave aside whether you were told about it or not, the fact is had you known at that time, you would have stopped the surgery, wouldn't you? A. Sir, with all due respect, it is not my role to stop the surgery based on medical parameters that are assessed by the anaesthetic team at the time. Q. Doctor-- A. If there was – sorry. Q. No, I'm sorry. Go on. A. If there was a surgical complication, such as uncontrolled bleeding or inability to instrument the spine or some sort of a complication related to the surgery, that would be my call to stop the surgery. Q. Doctor, I realise that you work in cooperation with your anaesthetist, you could hardly work otherwise, but the fact of the matter is that somebody must be the person who has the ultimate decision-making role, surely. Isn't that correct? A. That is correct. Q. And you, as the surgeon, have that role, don't you? A. These decisions are made in conjunction with the rest of the team and I seek the advice of the relevant person who is analysing these numbers to direct me. … Q. So then if the anaesthetist expressed alarm, ultimately the decision has to be yours as to whether or not you stop. A. That's correct." 1. Dr Gray said that he could not recollect being aware during the operation that Mr Hobson had a carbon dioxide level of 65 and that he could not recollect being told at about 20:50 that the breastplate of the Jackson table (a specially designed table for operating on patients in the prone position) was pressing on or compressing Mr Hobson's heart. Nor could he recollect being told that the pulmonary artery was being compressed, preventing proper perfusion of Mr Hobson's lungs with blood.

Dr Stephen Barratt 1. Dr Barratt indicated in his affidavit of 12 November 2015 that he had worked as a specialist anaesthetist for 22 years. 2. Dr Barratt said that on the evening of 17 November he received a call from Dr Sparks whilst Dr Sparks was in the operating theatre with Mr Hobson. Dr Barratt continued: " … Dr Sparks was concerned about Mr Hobson's consistent hypotension and ventilation issues during the surgery. He explained that Mr Hobson's carbon dioxide levels were not decreasing which meant increased dead space. Dr Sparks told me that Mr Hobson was in the prone position on a Jackson table during the surgery. In my view, if the breast plate of the Jackson Table was pressing on Mr Hobson, the cardiac compression would generate potential for hypotension. Dr Sparks expressed his concern about a high arterial carbon dioxide at the time. I think he said approximately 65mmHg. This is about 50% more than normal. This usually means inadequate ventilation and this issue had been excluded with multiple bronchoscopies, checking for breath stacking and pneumothorax. However, at the time Mr Hobson's end tidal carbon dioxide was only 30-25mmHg which means a significantly increased dead space ventilation. Inadequate ventilation on its own does not explain this. Therefore, I proposed to Dr Sparks that maybe a pulmonary artery was being compressed along with possible cardiac compression which would mean he would have a section of his lung which was being ventilated, but not perfused. The telephone call abruptly ended when Dr Sparks said 'I gotta go'." 1. Dr Barratt's evidence in cross-examination included the following: "Q. You say that Dr Sparks was concerned about Mr Hobson's consistent hypertension and ventilation issues during the surgery? A. Yes. He was very concerned. Q. Apart from being concerned, can you help us with how he expressed that, what he was concerned about? A. His speech was very pressured. He had multiple manoeuvres trying to suction the airway, bronchoscope the airway, check for breath stacking, checking for pneumothorax which is all critical events. Q. You said something was pressured. His? A. He was quite - his speech was quite pressured. He was - I could sense he was quite stressed for Chris. Q. He talked about his carbon dioxide levels not decreasing which meant increased dead space. Now, is that what he said or is that what you interpreted? A. That's what I interpreted. Q. Then you discussed his position on the Jackson table and you suggested that if the breast plate of the Jackson table was pressing on Mr Hobson, the cardiac compression would generate potential for hypertension? A. Yes, yes, it would. Q. How does that occur? A. If it's pressing on the main arteries coming out of the heart, the blood pressure will - can potentially fall basically. Q. If that occurs, what's the downside risk of that occurring? A. There might be critical organs which don't get perfused adequately. Q. He also expressed concern about a high arterial carbon dioxide content. A. Yes. Q. What is the significance of a high arterial carbon dioxide? A. Normally, that means you are not ventilating properly which is why they suction the airway, put a bronchoscope down the airway to check and did all those manoeuvres to check for ventilation. Q. Is this correct? That what had happened, as you understood it, Dr Sparks had carried out all the tests or checks, if you like, to see that everything was connected up and mechanically all was okay? A. Yes. He'd conducted all that and he was happy with it but he still could not explain the problem. Q. So your response was that probably, or maybe, a pulmonary artery was compressed along with possible cardiac compressions, it means his lung was being ventilated but not perfused? A. That is exactly correct. Q. What is ventilated but not perfused mean? A. It means that there is inability to eliminate carbon dioxide from the lung because there's no blood going through the alveolus and all this air is just coming into the lung and can't take the carbon dioxide out so the carbon dioxide is going to build up. Q. And the consequence of that is what? A. A carbon dioxide level of 65 is not a problem physiologically but for that to happen, you have to be pressing on a pulmonary artery in such a significant way that it's going to impede cardiac output and organ perfusion. Q. And the consequence of that is what? HIS HONOUR: If uncorrected you mean? MENZIES Q. If uncorrected? A. Critical end organ ischemia. Q. Critical? A. End organ perfusion or inadequate perfusion to an organ, damage, organ damage. Q. And the consequence of that in a longer term sense if these organs are damaged was what? A. Well, a low cardiac output state could damage the brain, the spinal cord, the kidneys, or the liver, for instance, potentially. … Q. Doctor Sparks told you that the various metabolic indicators were critical. A. Yes, yes. Q. Despite, apparently, adequate blood pressure and blood oxygen levels. That was one of his dilemmas, wasn't it? A. Yes, yep. Q. Then in those circumstances, it really wasn't appropriate, was it, to look at the blood pressure and blood oxygen levels alone when making a decision whether to persist or abandon surgery? A. I agree with that statement" (emphasis added).

Dr John Westbrook 1. Dr Westbrook gave evidence as an expert anaesthetist. His report of 6 November 2016 included the following: "Having taken the decision to proceed with surgery the anaesthetists correctly took a number of blood gas samples to measure the blood pH, oxygen and carbon dioxide levels and the blood lactate level. These demonstrated clear deterioration as the surgery progressed. Samples taken at 20:08 hrs and 20:21 hrs already demonstrated a very high carbon dioxide level despite their attempts at pulmonary ventilation with a double lumen tube. This was causing a significant respiratory acidosis. All attempts to improve the situation were proving to be unsuccessful. There was also early evidence of an increasing lactate level suggesting inadequate organ perfusion. Samples taken at 20:37 and 20:51 demonstrate significant further deterioration of all parameters such that the patient now had a profound respiratory and metabolic acidosis. Given that the anaesthetists had no clear means of reversing this deteriorating trend surgery should have been abandoned at this point, the wound closed and the patient turned prone. The sample taken at 21:01 had deteriorated further and eventual cardiovascular collapse was now inevitable in the absence of any corrective measures."

Dr Paul Forrest 1. Dr Forrest also gave evidence as an expert anaesthetist. 2. In his report of 26 October 2013 Dr Forrest gave the following answer in response to a question as to the likely cause of the cardiac collapse which resulted in Mr Hobson's paraplegia: "In my opinion, the cause of Mr Hobson's intraoperative collapse was acute right ventricular failure (RVF). This would account for the high central venous pressure, low oxygen saturation and low blood pressure that occurred at about 21:30h on 17 November. It would also account for the large difference in the carbon dioxide level measured in the patient's blood and his expired breath ('end-tidal carbon dioxide') prior to that time, the congested ('purple') appearance of his head that was observed when he was turned from prone to supine and the echocardiography findings at that time ('empty LV … RA full'). Mr Hobson's (sic) probably developed acute RVF because of predisposing factors and because of the use of the prone position for his surgery. The predisposing factors that would have contributed to acute RVF were his spinal deformity, which caused restrictive lung function and left lung collapse / infection due to bronchial compression. These factors would have caused the pulmonary arteries to constrict and thereby increased pulmonary vascular resistance (PVR). An increase in PVR causes the RV to dilate and may eventually decrease its capacity to pump blood (cardiac output). When Mr Hobson was turned prone, it proved very difficult to ventilate him effectively, despite confirmation of the DLT position and despite the use of a variety of different ventilation techniques. As soon as he was turned supine again, ventilation became much easier and his oxygenation, blood pressure and carbon dioxide levels rapidly normalized. The use of the prone position probably compromised his ventilation by increasing compression of the left main stem bronchus by his spine, due to the effects of gravity. His spine may also have been compressing pulmonary arteries and veins, which would also increase PVR and decrease cardiac output. Because of the difficulties in ventilation, the carbon dioxide level increased in his blood. This would also have significantly increased PVR, because raised carbon dioxide levels cause the pulmonary arteries to constrict. The combination of increased PVR and decreased cardiac output cause the blood supply to the RV itself to fall. When the blood supply to the RV falls below a critical level, acute, severe RVF can occur. However, it is not possible to accurately predict in an individual patient if, or when this will occur." 1. Dr Forrest gave the following answer to a question as to whether Dr Sparks provided a reasonable standard of anaesthetic management to Mr Hobson the operation: "Mr Hobson was a high-risk patient who required major emergency surgery at that time. He posed a very unusual and difficult anaesthetic challenge due to the significant compression of his left main bronchus by his spine and due to the requirement for prone positioning during surgery. Dr Sparks was well aware of the complexity of the patient's pre-existing problems, having attended his preoperative bronchoscopy (with Dr Barrett) (sic) in the intensive care unit. From the preceding, the use of a DLT to manage the extrinsic compression of the bronchus was reasonable, and confirmation of its position by repeated bronchoscopy was appropriate. The patient was appropriately monitored during the case, and the choice and dosages of anaesthetic drugs and intravenous fluids were also appropriate. The main clinical dilemma in this case was whether surgery should have been allowed to continue given the difficulties in ventilating the patient that were encountered before the severe deterioration that occurred at 21:30h. As noted above, the patient had been difficult to ventilate prior to this time due to compression of his left main bronchus, which was exacerbated in the prone position. However, given that the patient's surgery was considered to be sufficiently urgent that it needed to be performed out-of-hours, and given also that his lung infection would not have been expected to resolve until the compression of his left main bronchus was relieved by surgery, it was reasonable to continue the anaesthetic at that time." 1. In answer to a question as to whether Dr Sparks, in his anaesthetic management of Mr Hobson, acted "in a manner that was widely accepted in Australia by peer professional opinion as competent professional practice, at the time the service was provided", Dr Forrest opined that Mr Hobson "was appropriately monitored intra-operatively, and the anaesthetic drugs, dosages and fluid administration were also appropriate". He continued: "The management of the patient's critical deterioration at 21.30h was appropriate, as was the decision to abandon the procedure at that time. The anaesthetic management of Mr Hobson by Dr Sparks would therefore have been widely accepted by peer professional opinion in 2009 as competent professional practice."

The joint report of Drs Westbrook and Forrest 1. Dr Forrest was not specifically asked for the purposes of his individual report whether it would have been appropriate for Dr Sparks to have given the direction to terminate the operation at an earlier time than that at which it was given. However Question 14 recorded in the joint report asked Drs Westbrook and Forrest what steps, if any, should the anaesthetist have taken (particularly including recommending cessation of the surgery) in light of the indications available from Mr Hobson's blood pressure and decreased oxygen saturation at 18:50, 19:10, 20:35 and 21:20 hours. Their answers were as follows: "Answer to Question 14: Dr Westbrook feels that in view of the significant worsening of the plaintiff's haemodynamic state at 20:35, surgery should have been abandoned no later than 20:37, given the concurrent evidence of his worsening metabolic state as evidenced by blood gas analysis demonstrating a severe acidosis. In Dr Forrest's view, given that the plaintiff's surgery was considered to be potentially lifesaving at that time and was well advanced and also given that the period of haemodynamic instability and desaturation were transient at 20:35, it was reasonable to attempt to continue to improve the plaintiff's ventilation and haemodynamic state. At 21:30, however, it was clearly necessary to abandon surgery given the sudden, severe respiratory and haemodynamic instability that suddenly occurred at that time." 1. Question 21 enquired when (prior to achievement of its objective) should the surgery have ceased, if at all. The doctors' answers were as follows: "Answer to Question 21. It is the opinion of Dr Westbrook that the surgery should have been abandoned before 20:37 following the episode of hypotension that occurred at 20:30 hours, coupled with the plaintiff's severe and deteriorating metabolic state that was identified at 20:37 hours (by blood gas analysis). Dr Forrest is of the opinion that the surgery should have been abandoned when the plaintiff suddenly became hypoxic and hypotensive at 21:30." 1. The following evidence was given by the doctors in the course of their joint oral evidence: "MENZIES: What (sic) did that inevitability arise? Or put another way, in as much as it was inevitable and you've already said the surgery should have been stopped, at what point then do you say the surgery should have been stopped? WITNESS WESTBROOK: I – I mean I think at 2021 things were looking pretty grim but certainly at 2037 with a pH of seven and an increasing lactate I – it's my view that the surgery should have been abandoned at that point. MENZIES: Now, I'll just turn to Dr Forrest. Your comments about anything that Dr Westbrook has said thus far, doctor? WITNESS FORREST: Well, with a benefit of hindsight I think you couldn't argue that would have been preferable to abandon the surgery earlier than – than – than at the time that it was abandoned. That's a retrospective interpretation of the events that the anaesthetist were (sic) faced with at the time. You've also got to bear in mind that the key imperative for performing this case out of hours in the first place was that the attending doctors felt that if they didn't operate, his respiratory state would continue to worsen because of the compression of his main stem bronchus. And there was a reasonable expectation, I think, that if surgery had not been successful or not been performed to alleviate that obstruction, that the patient would have died from contractible respiratory failure. MENZIES: Thank you. WITNESS FORREST: Because of his worsening oxygenation state that Dr Westbrook has already alluded to. So, I think that there was – would have been a strong sense among the – the – the anaesthetists and attending doctors that – that – that surgery should proceed and that all attempts should be made to correct the underlying causes of his metabolic acidosis, which was being exacerbated by the fact that his ventilation proved so difficult in the prone position. And one thing that was done in order to improve his ventilation was to administer muscle relaxants, which had been withheld up until the period between 20 – 20 – 20.20 and 21.30, in order to attempt to improve his – his ventilation. Now, that in fact proved to be unsuccessful, because his carbon dioxide continued to climb, so as his carbon dioxide reached a level of over a hundred at – at – 2051. And I think really, the key to this is that – is that the difficulty in ventilation was already one of the key factors that was aggravating his metabolic acidosis because as carbon dioxide climbed, that led to an increase in his pulmonary-vascular resistance, which is the – basically the impedance against which the right ventricle has to eject. That in turn led to a reduction in right-ventricular function, right-ventricular performance, which decreases pulmonary blood flow. And of course, pulmonary blood flow is exactly the same as your cardiac output, so ultimately that right ventricular dysfunction led to the cardio-vascular collapse that occurred around 2130. … WITNESS FORREST: … [A]s I've already said, the reason why the surgery was done in the first place at that time was because it was felt that…(not transcribable)…would not be improved if his surgery had not gone ahead. So expectation would have been that he would have died at some point post-operatively in intensive care from…(not transcribable)…respiratory failure." 1. The following evidence was given after counsel suggested to Dr Westbrook that he was using hindsight in expressing his views: "WITNESS WESTBROOK: I've tried not to. I mean, inevitably, I know the outcome of the case and I can't forget that but also looking at the real time gas analysis during the surgery, I've tried to – well, I have considered how I would respond under those circumstances and I'm very clear in my own mind that given the severity of the acid-base disturbance that I would have insisted to the surgeons that the surgery was stopped. BURKE: Dr Forrest? How have you viewed this case? Have you looked back through the prism of hindsight? WITNESS FORREST: Well, I think, as I've said, that given the stakes that were thought to be involved at that time which would have been that if surgery was not completed that the patient would have died post-operatively in intensive care from refractory respiratory failure that the decision to continue the case based on hemodynamic monitoring and saturation monitoring, blood pressure monitoring and making further attempts to improve the patient's ventilation were reasonable."

Dr Bojidar Manasiev 1. Dr Manasiev was asked whether Dr Gray should have advised that the surgery be halted at four particular times, namely 18:50, 19:10, 20.35 and 21:20. Dr Manasiev said the following in relation to the last two of these times: "20:35 – there is a transient period of desaturation and relative hypotension, which from my understanding from the clinical notes and affidavits, was at the time of placement of a pedicle screw. It appears recognised that the downward pressure of the screw placement was affecting the respiratory and cardiovascular systems of the plaintiff. From Dr Sparks' Statement in Answer to Interrogatories, the hypotension resolves without any intervention. In my opinion, there are 3 reasons to justify not halting the operation at this time. First, there was a potentially identifiable and reversible cause of the hypotension and desaturation, in that of the downward pressure during screw insertion. Second, there was a quick resolution to normal values of blood pressure and saturation, presumably once the downward pressure was ceased. Third, the decision was balanced against the apparent necessity of the operation as a potential lifesaving technique. As such, it was not warranted by Dr Sparks or Dr Gray to halt the surgery at this time and would be considered widely accepted in Australia by peer professional opinion as competent medical practice to continue the surgery. 21:20 – although a drop in blood pressure to 90 mmHg on its own would not necessarily be a sufficient reason to halt the surgery, when coupled with a profound desaturation it becomes apparent that the patient is imminent danger of a cardiac and respiratory arrest. Dr Sparks appropriately advises halting the surgery. It is important to note that the management of the ventilatory and cardiovascular parameters are primarily the responsibility of the anaesthetist. The anaesthetist would be the first to comment on difficulties in achieving adequate ventilation and perfusion of the vital organs and as such direct the surgeon if the surgery would need to be halted to effectively resuscitate the patient. It would not be the responsibility of the surgeon to halt the surgery on the basis of haemodynamic or respiratory difficulties unless there was a question of the management of those difficulties by the anaesthetist. In my opinion Dr Sparks' management would be considered widely accepted in Australia by peer professional opinion as competent medical practice in directing Dr Gray to proceed at times 18:50, 19:10, 20:35 and halt at 21:20. As such it would be considered competent medical practice by Dr Gray to heed Dr Sparks' direction and proceed with the surgery at times 18:50, 19:10 and 20:35 and halt the surgery at 21:20." 1. Dr Manasiev was asked whether Dr Gray was negligent in continuing the operation between 19:10 and 21:20. He responded as follows: "In my opinion, Dr Gray was not negligent in continuing the operation in the circumstances pleaded. As outlined in my answer to 2, above, the management of the ventilator and cardiovascular parameters is the primary responsibility of the anaesthetist. Dr Sparks' management of the plaintiff in regards to directing Dr Gray to continue the surgery at 18:50, 19:10 and 20:35 and halt the surgery at 21:20 would be considered widely accepted in Australia by peer professional opinion as competent medical practice, with reasoning for each specific time as outlined in question 2 above. As such it would be considered competent medical practice by Dr Gray to heed Dr Sparks' direction and proceed with the surgery at times 18:50, 19:10 and 20:35 and halt the surgery at 21:20." 1. In cross-examination the following exchange occurred: "Q. What are the factors, you say, that would inform competent professional practice, with respect to anaesthetists and the continuance or otherwise of a surgery? A. Well, it's the whole gambit of all the haemodynamic parameters that you're looking at within a patient. Predominantly, the blood pressure and saturation, which are telling you how the organs are being perfused, but as well as that, all the attempts that are made, in this case, to improve ventilation: whether they are successful or non-successful, the response of all the blood gas analysis. It's a complicated gambit of numbers and figures that you're looking at."

The joint orthopaedic / neurosurgery / neurological expert evidence of Drs Johnson, Askin and Wilson-Macdonald 1. In the joint report, Drs Johnson, Askin and Wilson-Macdonald gave the following answers which are presently relevant: "4. Once commenced, when should the surgery have ceased? The experts agree that cardio respiratory problems arising in spinal surgery with the patient in the prone position occur infrequently but they have all experienced these problems necessitating the cessation of the operation. The experts agree procedures should have ceased when the anaesthetists were unable to maintain the metabolic state, ie satisfactory blood pressure and oxygenation. Dr Wilson-MacDonald notes that at 2037 blood gas analysis demonstrated a deteriorating metabolic state following an episode of hypotension at 2030. In his opinion surgery should have been discontinued shortly after this. … 18. In the light of (a) the information provided by the anaesthetists or (b) information provided by the spinal cord monitor (upon the assumption that the anaesthetists were informing the orthopaedic surgeon of the difficulties that they were experiencing and the spinal cord monitor was informing the orthopaedic surgeon of the inadequacies or absence of traces on the spinal cord monitoring) should the surgery have been ceased and, if so, when? The experts agree yes, when the anaesthetists reached the stage that they were unable to maintain satisfactory cardio respiratory parameters" (emphasis added). 1. In the course of their joint oral evidence, Dr Askin was asked whether, in the answer to Question 4 quoted above, the experts used the abbreviation "ie" in the sense of "that is" or to mean "eg", that is "for example". He responded as follows: "WITNESS ASKIN: I would have thought we could use it either way in that the metabolic state, be it the lactic acid or the PCO2, or the low PO2, and any other variable measured is in – closely interrelated to the blood pressure and oxygenation, so I suppose they're examples of the metabolic state rather than the sole metabolic state."

THE PRIMARY JUDGMENT 1. The primary judge held that the decision to operate on Mr Hobson on the evening of 17 November was justified. His Honour found that both Dr Gray and Dr Sparks "considered that there was a considerable risk that Mr Hobson might die if the surgery were not immediately performed", and that "Mr Hobson's condition before the operation was at worst associated with the strong possibility of his death if the operation was not brought forward". 2. His Honour also held that "the administration of vecuronium at 20.30 was reasonable in order to improve Mr Hobson's ventilation" and noted that it was "not in issue that Mr Hobson had not sustained the neurological injury of which he now complains by 20.30". His Honour further held that the decision to continue the surgery "at and from 20.30 was reasonable". 3. His Honour stated however that he was not satisfied that either Dr Gray or Dr Sparks "conformed to the relevant standard of care in failing to halt surgery before 21.25". He referred in this context to the opinion, expressed by Drs Johnson, Askin and Wilson-Macdonald in their joint report, that the operation should have ceased "when the anaesthetists reached the stage that they were unable to maintain satisfactory cardio respiratory parameters" (see [156] above). His Honour noted that these experts made no precise reference to a time when the surgery should have ceased, but he also noted that satisfactory cardio respiratory parameters "were not being maintained by 20.30". 4. His Honour then stated that Dr Barratt's evidence was "critical", and described the passage from his cross-examination quoted in [143] above as "extremely instructive". It seems that his Honour was particularly referring to Dr Barratt's evidence that Dr Sparks told him that "the various metabolic indicators were critical", and to his evidence that it was not appropriate to look at "the blood pressure and blood oxygen levels alone when making a decision whether to persist or abandon surgery". 5. His Honour continued: "It is important not to lose sight of the fact that Dr Sparks and Dr Gray were confronted with what was patently a distressing and fraught intraoperative emergency. It is difficult to over-emphasise just how awful it must have been at that time for all concerned. It is clear that Dr Sparks had attempted all of the anaesthetic manoeuvres in his armoury to correct the problem without apparent success. Criticism of these doctors in those circumstances may seem harsh. However, it is not in question that stopping the surgery when no obvious answer to the problems confronting the doctors was presenting itself would have avoided the damage. We know with hindsight that postural adjustment from prone to supine produced immediate resolution of these problems. That was something which in my opinion Dr Sparks and Dr Gray should have foreseen and acted upon. Failure to do so amounted to a want of reasonable care. It was in my view not appropriate to take the risk that something that could not be explained would or might somehow spontaneously resolve or improve. It is no answer to insist that the surgery was lifesaving in circumstances where Mr Hobson's respiratory difficulties at or after 20.30 had deteriorated below his pre-operative condition in ICU" (Judgment [242]). 1. His Honour stated his conclusions as follows: "Mr Hobson's blood gasses demonstrated a clear deterioration in his metabolic state as the surgery progressed. Samples taken at 20.08 and 20.21 demonstrated a very high carbon dioxide level despite various attempts at pulmonary ventilation with a double lumen tube. This was causing significant respiratory acidosis. There were also several episodes of hypotension and reduction in blood oxygenation during the surgery. From the early stages of the surgery, blood gasses disclosed evidence of an increasing lactate level suggesting inadequate organ perfusion. Blood gas samples at 20.37 and 20.51 indicated significant further deterioration of all parameters demonstrating to Dr Sparks a profound respiratory and metabolic distress. Dr Sparks was aware of this dangerous downward spiral in Mr Hobson's metabolic state. By 20.50 he had tried various means of reversing this deteriorating trend without success. In particular, maintenance of blood pressure and ventilation at reasonable levels after transient drops had failed to address Mr Hobson's dire and deteriorating condition. Dr Barrett correctly opined that the breast plate of the Jackson table was pressing on Mr Hobson creating cardiac compression and pulmonary artery compression, so that a section of lung was being ventilated but not perfused. Dr Sparks was negligent in not advising that surgery should have been abandoned no later than approximately 21.00. He was alive to Mr Hobson's metabolic deterioration which would have caused a reasonably competent anaesthetist to call a stop to the surgery. Had the surgery been paused or halted at that time, and Mr Hobson turned supine, he would not have suffered spinal cord damage. Dr Gray was also negligent for not ceasing surgery at that time. He was being alerted to the problems encountered by Dr Sparks and had the ultimate say in whether to continue or not. He was aware of Mr Hobson's metabolic deterioration which would have caused a reasonably competent orthopaedic surgeon to call a stop to the surgery. I reject the proposition, if Dr Gray advances it, that he was in all respects dependent and reliant upon Dr Sparks concerning Mr Hobson's condition or that the decision about whether to proceed with the surgery or abandon it was, or should have been, that of Dr Sparks alone. As the conclaves concluded, due to inadequate supply of oxygenated blood to Mr Hobson's spinal cord at 21.30, he suffered an ischaemic spinal cord stroke that resulted in paraplegia. In my opinion, Dr Gray and Dr Sparks each breached their duty to Mr Hobson by failing to terminate, or to recommend or advise the termination of the surgery on 17 November 2009 following earlier episodes of hypoxia and hypotension (occurring at or about 18.50, 19.10, and 20.35) in the face of related complications reported in the anaesthetic record after approximately 20.37 that evening. They failed at the very least to provide a proper standard of care by not immediately terminating the operation after the completion of Dr Sparks' telephone call with Dr Barratt in the face of the abnormalities shown on the anaesthetic record and with Mr Hobson evidently in uncorrectable respiratory and cardiovascular difficulties for as long as he remained in the prone position" (Judgment [261]-[267]). 1. His Honour said the following in relation to the appellants' reliance on s 5 I of the Civil Liability Act, which is concerned with the materialisation of an inherent risk: "In my opinion, this case cannot be conveniently decided under this section. In my view, having regard to the considerable evidence marshalled by all parties, the second stage of Mr Hobson's surgery was not attended by an inherent risk that he might suffer a cardiovascular collapse and vascular disturbance causing lower motor neurone injury, such as his anterior spinal artery syndrome, arising out of the circumstances as they occurred. Mr Hobson had a pre-surgical anatomical vulnerability to spinal cord stroke and the effects of hypotension. However, the damage sustained by Mr Hobson was not the materialisation of a risk that was inherent in undergoing posterior instrumented thoracolumbar surgery having regard to his medical condition at the time. … … Mr Hobson's paraplegia could in the circumstances have been avoided by the exercise of reasonable care and skill. Neurological injury, including paralysis, was an inherent risk of the surgery. A negligent failure to abandon the surgery, meaning a failure to exercise reasonable care and skill, before his paraplegia developed was not" (Judgment [248] and [251]). 1. The primary judge also rejected the respondent's defence under s 5 O of the Civil Liability Act, stating: "As I have previously observed, Dr Manasiev considered that Dr Sparks and Dr Gray were warranted in not halting the surgery before they did and would be considered by widely accepted Australian peer professional opinion to have conformed to competent medical practice by doing so. For the reasons I have given concerning the defendants' negligence, I reject that view" (Judgment [259]). 1. The primary judge treated as uncontroversial that Mr Hobson's paraplegia occurred after 21:15 and before 21:30. Accordingly, his Honour found that causation was established because if the operation had been abandoned by 21:15 at the latest (as, on his Honour's findings, it should have been), Mr Hobson would not have become a paraplegic.

DETERMINATION OF THE APPEALS

Dr Sparks' appeal on the negligence findings against him 1. The circumstances of the operation were as follows. 2. The curvature of Mr Hobson's spine, associated with his Noonan Syndrome, caused compression of his heart, and of major blood vessels. This rendered it difficult for his lungs to ventilate and for him to breathe. The November 2009 surgical operations were designed to correct the curvature, so as to alleviate the compression. 3. Mr Hobson's condition whilst in the ICU after the first operation, and before the second, indicated that the latter operation had to be undertaken urgently. 4. As the second operation (like the first) had to be performed whilst Mr Hobson was in the prone position, the compression was likely to be exacerbated during the operation. Dr Sparks described the compression as "certain to be worse in the prone position" and said that Mr Hobson "had a squashed heart since we turned him prone". It was therefore clear that at any time during the operation the compression could be relieved, at least to some extent, by terminating the operation and returning Mr Hobson to the supine position. 5. Mr Hobson's high blood carbon dioxide level at 20:30 to 20:35 was, as Dr Sparks described it in his answers to interrogatories, "very serious". It was serious because it indicated that there was significant pressure on a pulmonary artery, thereby impeding cardiac output and organ perfusion. Such low cardiac output could lead to organ damage, including to the spine (per Dr Barratt at [143] above). As recognised by Dr Forrest, the low pulmonary blood flow (which he said was the same as a low cardiac output) did in fact lead to "the cardio-vascular collapse that occurred around 21:30". That collapse caused Mr Hobson's paraplegia. 6. Dr Sparks made a decision at about 20:30 to administer vecuronium to attempt to correct Mr Hobson's carbon dioxide level, notwithstanding that the vecuronium would (and did) prevent spinal cord monitoring from being undertaken for the remainder of the operation. (Spinal cord monitoring is used to assist in identifying possible neurological compromise). The vecuronium was unsuccessful in correcting the carbon dioxide level. I note in passing that there was a conflict in the evidence, which the primary judge did not resolve, as to whether the monitoring had already failed by the time the vecuronium was administered (Judgment [184]-[186]). 7. Dr Sparks then tried, unsuccessfully, to identify and correct the carbon dioxide problem by a variety of other means. However by 20:50, when he called Dr Barratt and Dr Marshman, he had exhausted all possibilities. Those doctors were unable to suggest any other intra-operative steps to correct the problem. 8. At least by 20:50, Dr Sparks formed the view, consistent with that expressed to him at about that time by Dr Barratt, that the cause of Mr Hobson's high carbon dioxide was "cardiac and not the ventilation" (see [122] above), that is, that Mr Hobson's lung was not being fully perfused by blood. There was therefore "dead space" in it. As noted earlier, this was a serious problem, indicating the potential for lack of proper blood supply to cause damage to his organs, including his spinal cord. Dr Westbrook considered that a blood gas sample taken at 21:01 indicated that the problem had worsened and that "further and eventual cardiovascular collapse was now inevitable in the absence of any corrective measures". There was no evidence directly contradicting this opinion. What Dr Westbrook saw as the inevitable occurred at about 21:25 when Mr Hobson suffered a cardio-vascular collapse. 9. There was no evidence that between his two brief phone calls (commencing at about 20:50) and the sudden blood pressure drop (at about 21:25) Dr Sparks took any steps to correct the cardiac problem he had identified. Nor was there any evidence that he could have taken any steps that would have corrected the problem, short of directing termination of the operation and having Mr Hobson returned to the supine position. 10. Dr Sparks took the view that, notwithstanding the existence of the carbon dioxide, and therefore cardiac problem, he should not direct termination of the operation whilst Mr Hobson's oxygen and blood pressure were in the normal to high range. He stated that this was "an urgent operation to save life" and the "risk of not going ahead exceeded the risk of going ahead" with the procedure (see [130] above). He also referred to his assumption that "… the cardiac compression would always be there, unless we corrected it", and that, in order to "make [Mr Hobson] better, we had to make him worse in the short term". Dr Sparks accepted that the problem of cardiac compression could be relieved by halting the surgery and turning Mr Hobson into the supine position. He said however that this would only have deferred Mr Hobson's cardiac compression problem, not solved it. 11. From about 20:50 onwards, Dr Sparks thus elected to be guided only by the oxygen and blood pressure readings as his criteria for stopping the operation, thereby, effectively, ignoring the carbon dioxide, and therefore cardiac, problem. He took this view notwithstanding that (1) the carbon dioxide readings indicated that Mr Hobson might suffer catastrophic injury if they continued, (2) he believed that it would be several hours before the operation would be finished, and (3) Mr Hobson's carbon dioxide level (and therefore blood circulation) was capable of being substantially improved by terminating the operation and returning Mr Hobson to the supine position. Further, from about 20:50 Dr Sparks treated the oxygen and blood pressure readings as the only relevant indicators, as Dr Forrest acknowledged, these are the main, but not the only, relevant indicators. 12. In assessing the reasonableness of Dr Sparks' conduct, the tense and difficult situation he was in must be fully recognised. Nevertheless, like the primary judge, I consider that by not directing or advising termination of the operation prior to at least 21:20, Dr Sparks failed to provide the standard of reasonable care expected of a specialist anaesthetist (see Rogers v Whitaker (1992) 175 CLR 479 at 483; [1992] HCA 58). I have taken this view for the following reasons. 13. First, Dr Sparks' failure to direct or advise termination of the operation was not limited to a short period of time. Dr Sparks' call to Dr Barratt took place at about 20:50, and his call to Dr Marshman took place at about 20:55. Although the evidence does not indicate the precise duration of these calls, it appears that they were brief. Even allowing 10 minutes in total for the calls, Dr Sparks still had at least 20 minutes (until 21:20) between the time at which he had exhausted all possibilities for correcting Mr Hobson's carbon dioxide level, and the time at which Mr Hobson's blood pressure and oxygen level dropped (21:25), causing Dr Sparks to advise that the surgery be halted. More likely, the calls were briefer and that period was therefore longer. 14. Secondly, although the operation was urgent and Mr Hobson's pre-operative condition might ultimately have caused his death or serious injury, there was no suggestion that such outcomes would eventuate if the operation were not completed within a matter of a few hours. For example, it was apparent from Dr Gray's evidence that it would have been acceptable for the operation to proceed the following morning, the reason for it being performed on the evening of 17 November being related to the unavailability of personnel the next day. Similarly, Dr Sparks gave evidence that he thought the operation was urgent in the sense that it should be done within 24 hours of the discussion that occurred at 2pm on 17 November. 15. In essence, I consider that Dr Sparks made an unreasonable decision to ignore a serious and imminent intra-operative danger to Mr Hobson's well-being when Dr Sparks knew that the other risk with which he was concerned (namely the risk to Mr Hobson if the operation were not completed) did not have the same immediacy. As the primary judge found, it was "not appropriate to take the risk that something that could not be explained [and had been unable to be rectified] would or might somehow spontaneously resolve or improve" (Judgment [242]). This was particularly inappropriate given that there were several hours remaining before the operation would be completed, and that Dr Sparks knew that serious consequences could (and, as it transpired, did) result from the continuation of the cardiac compression which caused Mr Hobson's high carbon dioxide readings. 16. Thirdly, Dr Sparks had to assess and respond to the immediate danger to Mr Hobson (rather than the more remote risks that could eventuate if the operation was not completed) because Dr Sparks' duty as principal anaesthetist was to protect the patient's well-being whilst the operation was in progress. His role was thus essentially to manage and respond to the ventilatory and cardio-vascular indicators of Mr Hobson's condition. It was not for Dr Sparks to assess the urgency of the operation and decide that it justified a serious and immediate intra-operative risk to Mr Hobson being ignored, at least not without consulting Dr Gray who, as principal surgeon, was head of the surgical team. There was no evidence to indicate that such consultation occurred between 20:30 and before 21:25, if at all. Instead, Dr Sparks' evidence was that "[b]ecause it was emergency surgery I had resolved in my mind that while the oxygenation and blood pressure were normal to high it was appropriate for the surgery to continue" (emphasis added). 17. My conclusion is consistent with the expert evidence of Dr Westbrook, who considered that the blood gas samples taken at 20:37 and 20:51 demonstrated that by then Mr Hobson "had profound respiratory and metabolic acidosis" and that, there being "no clear means of reversing this trend surgery should have been abandoned at this point" (presumably a reference to 20:51). Dr Wilson-MacDonald considered that the operation should have been abandoned even earlier, at 20:37, in light of the blood gas analysis results obtained at that time (see the joint report quoted in [156] above). 18. I do not consider that Dr Forrest's evidence requires a different conclusion to that which I have reached. In the joint expert anaesthetists' report, Dr Forrest opined that, in the circumstances that existed at 20:35, it was "reasonable to attempt to continue to improve the plaintiff's ventilation and haemodynamic state". Similarly, in his oral evidence, he said that "it was reasonable to continue and to make further efforts to alleviate both [Mr Hobson's] "respiratory and metabolic acidosis" (ie the consequences of Mr Hobson's high carbon dioxide level). However neither in the joint report, nor in his own report and oral evidence, did Dr Forrest focus on the circumstances that existed after Dr Sparks' calls to Drs Barratt and Marshman at about 20:50; namely that all possibilities for improving Mr Hobson's condition (short of terminating the operation) had been exhausted, and that Mr Hobson's condition was deteriorating and could not be described as transient. The existence of those circumstances was evident from Dr Sparks' agreement in cross-examination that when blood gas samples were taken at 20:37 and 20:51 Mr Hobson had "a definite metabolic and respiratory acidosis," that Dr Sparks had "no clear means of reversing this", and that there was "a deteriorating trend" in Mr Hobson's condition. 19. The existence of these circumstances contradicts an assumption upon which Dr Forrest founded his opinion, expressed in the joint report and oral evidence, that it was reasonable for the operation to continue after 20:30 ([147] and [150] above). This assumption was that there were still steps that could be, but had not yet been, taken to improve Mr Hobson's carbon dioxide level, and thereby correct the underlying cardiac problem that it reflected. 20. Moreover, a reason Dr Forrest gave for his opinion was that the surgery "was considered to be potentially life-saving at that time". Dr Forrest did not however address the question of whether the anaesthetist should assess and take account of such a factor without consulting the principal surgeon. 21. Like the primary judge, I therefore do not consider that Dr Forrest's evidence provided a compelling guide to the proper outcome of the negligence claim against Dr Sparks. 22. Dr Manasiev's evidence suffered from similar deficiencies. Moreover, he was asked to provide an opinion as to whether the surgery should have been halted at four specific points of time (18:50, 19:10, 20:35 and 21:20) (see [153] above). He did not, at least in terms, express a view as to the continuation of the operation in the specific period 20:50 to 21:20, when all possibilities for rectifying Mr Hobson's carbon dioxide level problem had been exhausted. 23. For these reasons, I consider that Dr Sparks breached the duty of care he owed to Mr Hobson.

Dr Gray's appeal on the negligence finding against him 1. In determining Dr Gray's appeal, it is particularly important to recognise his role as the principal surgeon leading a team of specialist medical staff. Although as head of that team he had ultimate authority to make significant decisions regarding the operation, he was entitled to rely on the other team members to perform their duties. 2. The surgeon's role as a member of a team was described in Ingram v Fitzgerald [1936] NZLR 905 at 913-4 as follows: "The theatre sister and the assistant nurses are supplied by the private hospital where the operation is performed, and they have thus independent duties to perform. In the circumstances of this case, we think the proper inference is that the defendant [surgeon] did not undertake personally to do all the work necessarily involved in the operation … He must rather have undertaken to perform the operation in the hospital selected, and with the appliances there available, and with the assistance and co-operation of qualified, competent, and experienced nurses attached thereto. It is true that he was in supreme control, and that he had the right and the duty to intervene and could do so. But those subject to that control were skilled collaborators with independent duties, and he did not find it necessary, nor would he expect to find it necessary to intervene to direct the manner in which they discharged those duties. They were not his delegates in the sense that they were there to do work which he had contracted to do or to have done. They were, for general purposes, the servants of the hospital, but in the theatre they were subject to his directions. In no sense, then, is it a proper inference from the facts that the doctor undertook personally to carry out that part of an operation which, in practice, falls to the nurses. There was no delegation, then, in the ordinary sense; for he did not intend, and could not be taken to have assumed, to do their work or to have it done." 1. This passage was referred to with approval by this Court in Elliott v Bickerstaff (1999) 48 NSWLR 214; [1999] NSWCA 453. At issue in that case was whether a surgeon had failed to exercise due care and skill in relation to sponges which were left in a patient's abdominal cavity after an operation concluded. The Court held that the surgeon, although "the master of ceremonies", was entitled to rely on theatre staff to ensure that the sponges were removed (at [103]). 2. Whether such reliance is justified in any particular case must of course depend upon the circumstances. In the present case, the problem that arose fell within the responsibilities of Dr Sparks as principal anaesthetist. The primary judge did not find that Dr Gray had an obligation to apprise himself either of the problem, or of information that might have alerted him to its existence, in the absence of Dr Sparks putting him on notice of it. On appeal, Mr Hobson does not contend that any such finding should have been made. 3. Instead, critical to the primary judge's conclusion that Dr Gray was negligent were his Honour's findings that during the operation Dr Gray "was being alerted to the problems encountered by Dr Sparks" and "was aware of Mr Hobson's metabolic deterioration" (Judgment [265]). 4. It does seem unlikely that, in the period between approximately 20:30 (when vecuronium was administered) and 21:20 (approximately the latest time at which Mr Hobson's injury could have been avoided by termination of the operation) Dr Sparks would not have said anything to Dr Gray regarding Dr Sparks' serious concerns about Mr Hobson's carbon dioxide readings. Nevertheless, there was no evidence that Dr Sparks did so, and therefore no evidentiary basis for the primary judge's findings. As a result, the negligence finding against Dr Gray cannot stand. 5. In his written submissions, Mr Hobson contended that: "It would be naïve to suggest that with Dr Sparks at the patient head and Dr Gray at his spine that Dr Gray was somehow not aware of the difficulties Dr Sparks was experiencing establishing ventilation, the more so when Dr Sparks abandoned his position at the patient's head to make an urgent and stressed call to Dr Barratt." 1. In those submissions however Mr Hobson did not refer to any evidence of that awareness, except for the following question and answer in Dr Gray's cross-examination: "Q. Doctor, at 20.08 there were very high carbon dioxide levels despite the attempts at pulmonary ventilation with a double lumen tube, and this was causing a significant respiratory acidosis, wasn't it? A. At the time I was concentrating on my surgery and I was not entirely informed and aware of the, the nuances and details of these changes." Whilst this answer's references to not being "entirely informed" and to "nuances and details" raise a question as to whether Dr Gray was aware of the carbon dioxide problem at a higher level of generality, this evidence does no more than that. The evidence is insufficient to establish the awareness necessary to make good Mr Hobson's contentions. 1. Moreover, none of the three references given by Mr Hobson's senior counsel in oral argument constituted such evidence. The first related to a discussion at about 20:30 concerning the administration of vecuronium (transcript 139.42), the second indicated that during the operation Dr Gray was getting "feedback" concerning Mr Hobson's blood pressure and oxygenation (transcript 149.32), and the third concerned additional information (including information about Mr Hobson's carbon dioxide levels) conveyed to Dr Gray at about 21:25, shortly before the operation was terminated (Dr Gray's answer to interrogatory 31(d); see also above at [133]). 2. Thus Dr Gray's evidence regarding information he received during the operation about Mr Hobson's vital signs did not extend to his carbon dioxide readings. The information covered only what were undoubtedly the main indicators, being blood oxygenation and blood pressure (see [137] above). 3. Certainly, Dr Gray was involved in the discussion at about 20:30 which led to the administration of vecuronium to attempt to reduce Mr Hobson's carbon dioxide level. However, in the absence of any suggestion to him to the contrary, Dr Gray was entitled to assume that this parameter had become satisfactory. Neither the primary judge nor any expert witness suggested otherwise. 4. In summary, the surgery that took place on 17 November was complex, protracted and difficult. It was Dr Sparks' role to monitor indicators of Mr Hobson's condition during the surgery, the two main ones being Mr Hobson's blood oxygenation and blood pressure, although other indicators were relevant. At least in respect of the other relevant indicators, Dr Gray was entitled to rely on Dr Sparks to inform him of any matter of concern without Dr Gray making any inquiry. There is no evidence that Dr Sparks did so in the period 20:50 to 21:20, and the evidence did not indicate that any matter came to Dr Gray's notice during that time that should have caused him to make an inquiry as to Mr Hobson's carbon dioxide level. Without such information, Dr Gray was not negligent in failing to direct termination of the operation during that period. When Dr Sparks did advise termination of the operation at around 21:25, Dr Gray promptly did so. Dr Gray's appeal on liability therefore succeeds.

Section 5 I of the Civil Liability Act – inherent risk 1. The terms of s 5 I are quoted in [114] above. As this Court pointed out in Paul v Cooke (2013) 85 NSWLR 167; [2013] NSWCA 311, the terms of the section raise a number of issues as to their meaning. 2. For present purposes, it is sufficient to refer to Leeming JA's description (with which Ward JA agreed) of the question that s 5 I required to be answered in that case, namely whether "the 'risk of something occurring', that is the 'risk of intra-operative rupture followed by stroke', could have been avoided by the exercise of reasonable care and skill" (at [67]). To the same effect was Payne JA's formulation of the relevant question in The Nominal Defendant v Buck Cooper [2017] NSWCA 280 at [112]: "did the respondent face the same inevitable risk even if Mr Lament [in whose stead the Nominal Defendant stood] exercised reasonable care and skill?". 3. The facts in Paul v Cooke, a rare case in which s 5 I operated to exempt a defendant from liability, were as follows. In 2003 the defendant radiologist negligently failed to diagnose the plaintiff as having an intercranial aneurysm. In 2006 the aneurysm was diagnosed and the subject of an operation during which the plaintiff suffered a cranial rupture. That rupture did not result from any lack of reasonable care in performance of the operation, rather it involved the materialisation of a risk associated with the operation. The plaintiff alleged that, had she been diagnosed in 2003, the operation that would have been performed at that time would more likely than not have resolved the aneurysm without complication. Therefore she argued that she was exposed to risks in 2006 that she would not have been exposed to but for the radiologist's negligence in 2003. The Court held that there was no material increase in the risks associated with the type of operation that was performed in 2006 as compared to that which would have been performed in 2003. Further, the Court held that the intra-operative risk of cranial rupture was a risk associated with the type of operation that the plaintiff underwent in 2006, whenever such operation may have been performed. The risk that materialised was therefore not created by the defendant radiologist's negligence and constituted an inherent risk of the type of operation performed in 2006. The Court accordingly found that s 5 I applied to exempt the radiologist from liability. 4. In the present case, the appellants contended that there existed an unavoidable risk of neurological injury (including paralysis), that this risk was an inherent risk of the surgery and that the risk materialised. They argued that, in these circumstances, s 5 I exempts them from liability. 5. There is undoubtedly a risk that neurological injury may occur in the course of complex surgery such as that performed in the present case. It may be assumed that some such injuries may occur despite all reasonable care being taken and are therefore unavoidable. Other such injuries may occur, or the risk of such injuries may be increased, due to the failure of one or more members of the surgical team to conduct the operation with reasonable skill and care, as I have held to be the case here. It would be inconsistent with the express words of s 5 I(2) for the section to apply in respect of the latter injuries. In Paul v Cooke at [9] and [77], the Court expressly refrained from opining on such a situation, as it did not arise in that case. There, the operation was conducted with reasonable care. 6. The question then arises as to what scope exists for the operation of s 5 I. In my view, there is very little. If there is a finding of negligence by the defendant, the section will usually be inapplicable. Paul v Cooke is however an example, albeit likely to be rare, of a case in which the section does apply. 7. For these reasons I conclude, as did the primary judge, that s 5 I did not provide the appellants with a defence to Mr Hobson's claim.

Section 5 O of the Civil Liability Act – peer professional opinion 1. The terms of s 5 O are quoted in [114] above. The section provides a defence, with the onus of proof lying on the defendant (Sydney South West Area Health Service v MD [2009] NSWCA 343; (2009) 260 ALR 702 at [21]). It is unnecessary to consider the application of s 5 O to the claim against Dr Gray as I have concluded that the evidence does not establish that Dr Gray was negligent. The position so far as Dr Sparks is concerned is as follows. 2. In McKenna v Hunter & New England Local Health District [2013] NSWCA 476; (2013) Aust Torts Reports 82-158, with the concurrence of Beazley P, I concluded that s 5 O was inapplicable to exempt the defendant in that case from liability. The decision was reversed by the High Court on other grounds (Hunter and New England Local Health District v McKenna (2014) 253 CLR 270; [2014] HCA 44), and the High Court did not consider s 5 O. The appellants submitted that this Court's decision in McKenna was wrong insofar as it dealt with s 5 O, and that s 5 O does not depend on the existence of a "practice" at the time the conduct occurred. This is incorrect for the following reasons. 3. Section 5 O uses the past tense ("at the relevant time … was widely accepted") to refer to the relevant peer professional opinion. Thus, the opinion about the manner in which the defendant acted must have existed, and been widely accepted, at the time the conduct occurred. It is not enough that experts called to give evidence consider that the conduct was reasonable and that it would have been so regarded by other professionals if they had been asked about it at the time of the conduct. 4. In McKenna, I described the background to the enactment of s 5 O, referring in particular to Bolam v Friern Hospital Management Committee [1957] 1 WLR 582; [1957] 2 All ER 118, Sidaway v Board of Governors of the Bethlem Royal Hospital [1984] 1 QB 493, Dobler v Halverson (2007) 70 NSWLR 151; [2007] NSWCA 335 and Rogers v Whitaker. I concluded as follows: "160 To establish a defence under s 5O a medical practitioner needs to demonstrate, first, that what he or she did conformed with a practice that was in existence at the time the medical service was provided and, secondly, to establish that that practice was widely, although not necessarily universally, accepted by peer professional opinion as competent professional practice (emphasis in original). 161 One can see in the facts of the cases that I have mentioned the possibility that what was done accorded with a practice. For example, there may well have been a practice in some part of the profession, in Bolam to use electro-convulsive therapy to treat depression; in Sidaway to give or not to give a warning of risks in respect of the type of spinal operation in question; in Rogers v Whitaker to give or not to give a warning of risks in respect of the type of eye operation conducted on the plaintiff and in Dobler to refer or not refer a patient for an ECG and/or to a cardiologist on detection of a heart murmur." 1. I then referred to the wide variety of circumstances that were relevant to the reasonableness of the defendant's conduct in that case, and continued: "165 In summary, the section is directed to something, namely a practice, that was in existence at the relevant time, here July 2004. Whilst at that time there were no doubt many practices in the medical profession concerning the manner in which operations were performed, the types of treatments that were administered, the circumstances in which tests were ordered, the circumstances in which warnings were given and other matters, the evidence here did not identify any such practice that was relevant in the present case. In light of the wide variety of circumstances bearing upon the decision to discharge Mr Pettigrove, it would have been surprising if it had done so. It is unlikely, to say the least, that there would have occurred in or before 2004 a number of situations in which there were sufficient features in common with the present case to enable it to be said that there was a practice concerning how such a situation was to be dealt with by a competent medical practitioner." 1. These observations are applicable to the present case, which does not relate (at least so far as the issues of negligence on appeal are concerned) to any particular point of medical practice, such as the use of a particular drug, surgical technique or item of surgical equipment. Rather, as in McKenna, determination of the issue of negligence requires reference to a variety of factual considerations including: • The significance of an elevated blood carbon dioxide level when oxygen and blood pressure readings were normal to high; • The urgency of the operation, bearing in mind Mr Hobson's pre-existing condition; • The exhaustion of possibilities, short of termination of the operation, for remedying the carbon dioxide problem and its underlying cause, being the compression of blood vessels preventing blood fully perfusing the lungs. 1. Evidence from a number of witnesses highlighted the unusual nature of the operation. For example, Dr Barratt had never seen this type of surgery performed on a patient with Noonan Syndrome and Dr Forrest described the operation as involving "a very unusual and difficult anaesthetic challenge". It can be assumed that the particular events that occurred in the course of the operation rendered the situation even more unusual. 2. The appellants submitted that the following evidence given by Drs Forrest and Manasiev demonstrated that s 5 O was applicable. 3. In his report, Dr Forrest stated: "The patient was appropriately monitored intraoperatively, and the anaesthetic drugs, dosages and fluid administration were also appropriate. The management of the patient's critical deterioration at 21:30h was appropriate, as was the decision to abandon the procedure at that time. The anaesthetic management of Mr. Hobson by Dr. Sparks would therefore have been widely accepted by peer professional opinion in 2009 as competent professional practice." 1. It is apparent from the manner in which this evidence was expressed that Dr Forrest was saying, in effect, that in his view the appellants acted reasonably and that he considered that a wide range of his professional peers would be likely to take the same view. He did not point to an established practice, and opine that it was followed in the present case. Indeed, it is probable that he could not have expressed such an opinion because, as in McKenna (see [165] quoted above at [213]), it is unlikely that "there would have occurred … a number of situations in which there were sufficient features in common with the present case to enable it to be said that there was a practice concerning how such a situation was to be dealt with by a competent medical practitioner". 2. Dr Manasiev stated in his report that Dr Sparks' management of Mr Hobson in the operation "would be considered widely accepted in Australia by peer professional opinion as competent medical practice". He elaborated on this in cross-examination in the following exchange: "Q. What are the factors, you say, that would inform competent professional practice, with respect to anaesthetists and the continuance or otherwise of a surgery? A. Well, it's the whole gambit of all the hemodynamic parameters that you're looking at within a patient. Predominately, the blood pressure and saturation, which are telling you how the organs are being perfused, but as well as that, all the attempts that are made, in this case, to improve ventilation: whether they are successful or non-successful, the response of all the blood gas analysis. It's a complicated gambit of numbers and figures that you're looking at." 1. My comments concerning Dr Forrest's evidence on this topic are equally applicable to that of Dr Manasiev. Whilst Dr Manasiev gave reasons as to why he thought that the conduct was reasonable, he did not point to any particular practice. Expert evidence that says no more than that the expert considers the defendant to have acted reasonably, and in a way that would be widely regarded as acceptable, is insufficient to establish the existence of a "practice" for the purpose of s 5 O. Accordingly, as the primary judge held, s 5 O does not exempt Dr Sparks from liability for his negligence.

DAMAGES

Past domestic assistance 1. Mr Hobson claimed at first instance that, from the time he commenced rehabilitation at Ryde Rehabilitation Hospital in 2010 to the date of the judgment at first instance, he required 40 hours per week gratuitous domestic assistance and personal care. The appellants submitted that the evidence only established a need of 20 hours per week. The primary judge found that the need was 30 hours per week. 2. On appeal, the appellants submitted that the primary judge's allowance was excessive because it exceeded the care needs estimated by Mr Hobson's sister, Ms Siobhan Hobson, who is Mr Hobson's principal carer. The appellants rely on the following exchange in Ms Hobson's oral evidence: "Q. Are you able to give an estimate of overall how much time you would spend a week on these various tasks that you've nominated? A. 20 or more, maybe." 1. In relation to this evidence, the primary judge referred to the inherent difficulty of estimating the amount of time taken to provide care where the carer's principal concern is, understandably, providing the care rather than noting the time involved. His Honour continued: "It is in my opinion a mistake to underestimate the challenges for someone such as Mr Hobson, who is rendered a paraplegic, and who is required to come to terms with the mental and physical consequences of that dreadful discovery. Accommodating to life with such a significant disability is too easily discounted as an everyday vicissitude in the life of the injured person. In my opinion, it is not a mistake to err on the side of overstating, rather than understating, the hours of assistance that Mr Hobson required following his discharge from rehabilitation. His sister was very conservative in her evidence in my assessment and played down what the true difficulties probably were" (Judgment [311]). 1. In my view it was open to his Honour to adopt this approach. In addition to the part of Ms Hobson's oral evidence relied upon by the appellants, his Honour had before him affidavits of Mr and Ms Hobson describing what was involved in Mr Hobson's care. Moreover, his Honour was able to observe both witnesses give evidence. 2. His Honour's decision was an evaluative one, necessarily requiring an impressionistic assessment of the whole of the evidence (Harrison v Melhem (2008) 72 NSWLR 380; [2008] NSWCA 67 at [67], [76]). This Court will not interfere with such a decision unless it involves a misunderstanding of the evidence, an error of principle, or is outside the range of decisions that might reasonably be arrived at. None of these criteria for intervention have been satisfied. 3. I add that the appellants' additional submission, which focused on the composition of Ms Hobson's estimate of the time required for Mr Hobson's care, should likewise be rejected. It was for the primary judge to assess the detail of the relevant evidence and, in the absence of any error of principle or clear unreasonableness, this Court should not intervene.

Future domestic assistance 1. The appellants made three submissions in relation to the primary judge's assessment of Mr Hobson's needs for future domestic assistance. 2. First, they submitted that his Honour's estimate of the hours of assistance needed was erroneous because his Honour relied on an analogy between the time taken for care of an infant and that required for care of a disabled and paraplegic adult, when there was no evidence of the amount of time the care of an infant required. 3. I reject this submission. The primary judge was entitled to rely on his experience of life to make a practical assessment of the evidence before him, which included evidence-in-chief of Dr Yeo, a rehabilitation expert. Dr Yeo's assessment of the hours of care needed was ultimately adopted by his Honour. His Honour's analogy did no more than indicate that he thought that Dr Yeo's assessment was realistic. 4. Secondly, the appellants complained that the primary judge did not take into account concessions made by Dr Yeo in cross-examination, particularly as to the time required for house cleaning. However, as his Honour had referred to those concessions earlier in his judgment, it cannot be concluded that he overlooked them. His Honour's task was to make a practical assessment of the whole of the evidence. In doing so, he was not bound to accept or reject any particular part of it. It was open to his Honour to find, as he clearly did, that Dr Yeo's evidence-in-chief was more realistic than parts of his evidence in cross-examination. Accordingly, this submission should be rejected. 5. Thirdly, the appellants submitted that the primary judge erred in not basing his calculations on the hourly fee for domestic assistance charged by a firm named Absolute Domestics, which was referred to in the expert report of Ms Tchan (who was called by the respondent). Instead, his Honour based his calculations on the higher rate used by Ms Hardy (who was called by the appellants). This rate was slightly less than that given by Ms Alach (who was also called by the respondent). It was open to his Honour to take this course because the report which identified the rate charged by Absolute Domestics was dated almost four years prior to the hearing before his Honour, whereas the reports of Ms Hardy and Ms Alach were provided in October 2015. 6. By means of Dr Gray's written submissions in reply on the appeal, the appellants submitted, for the first time, that the primary judge failed to take into account evidence of Mr Hobson's ability to undertake domestic tasks prior to his paraplegia. The appellants conceded however that in the Court below they did not seek to take advantage of the proposition that Mr Hobson had such abilities (Dr Gray's reply submissions [25]). In these circumstances, this Court should not conclude from the absence of express reference to this evidence that the primary judge did not take it into account as part of the evidence from which he formed a (necessarily impressionistic) conclusion as to Mr Hobson's future needs resulting from his injury. The submission should therefore be rejected.

Motor vehicle expenses 1. After taking into account a variety of circumstances, the primary judge concluded that a buffer of $240,000 for motor vehicle expenses was appropriate. His Honour had to consider matters such as when Mr Hobson would require use of a vehicle and the type of vehicle that he would need, bearing in mind the extent of his disabilities. 2. His Honour took the view that the amount of $291,730 claimed by Mr Hobson was excessive because it involved some double-counting. He also concluded that the figure of $125,000 that the appellants accepted as justified was insufficient. His Honour concluded that a buffer of $240,000 was appropriate. 3. The appellants submitted on appeal that there was no evidence to found the primary judge's assumption that Mr Hobson desired to drive a vehicle modified to account for his disabilities. However, in his affidavit Mr Hobson stated that he was "very motivated" to drive a modified vehicle, but that "financially I am unable to do so at the moment" ([51]). 4. The appellants' challenge to the buffer his Honour adopted for motor vehicle expenses did not otherwise raise any point of principle. Nor did the appellants demonstrate that the buffer was outside the range of those reasonably available to be adopted. Their challenge must accordingly be rejected.

CONCLUSIONS AND ORDERS 1. For the reasons I have given Dr Sparks, but not Dr Gray, is liable to Mr Hobson for damages and the appellants' challenges to the primary judge's assessment of those damages fail. 2. I propose the following orders: 1. Dismiss Dr Sparks' appeal with costs; 2. Allow Dr Gray's appeal; 3. Set aside orders 1 and 2 made at first instance so far as they relate to Dr Gray; 4. Judgment for Dr Gray on the respondent's claim against him. 5. Order the respondent to pay Dr Gray's costs of the proceedings at first instance and on appeal; 6. Grant the respondent a certificate under the Suitors' Fund Act 1951 (NSW) in relation to Dr Gray's appeal. 1. SIMPSON JA: In November 2009 the respondent, Brendan Hobson, underwent spinal surgery at the Royal North Shore Hospital ("RNSH"), designed to be performed in two stages. The first stage was performed uneventfully on 13 November. The second stage commenced in the evening of 17 November but was not completed. During the course of this surgery a complication occurred which led to the premature termination of the surgery. As a result of the complication the respondent is now permanently paraplegic. 2. In 2013 the respondent commenced proceedings in the Supreme Court of NSW. He claimed that his paraplegia was caused by negligence and/or breach of contract in the treatment afforded to him by RNSH, by the principal orthopaedic surgeon who performed the surgery (Dr Randolph Gray), by a neurophysiologist who was engaged to provide spinal cord monitoring during the course of the surgery (Dr Jim Lagopoulos), and by the principal anaesthetist (Dr Christopher Sparks) engaged to provide anaesthetic services for the purposes of the surgery. Each was named as a defendant in the proceedings. It will be necessary to say more in due course about the nature of the respondent's allegations against the various defendants. 3. A trial commenced on 7 November 2016. On the tenth day of hearing, 21 November, the proceedings against RNSH and Dr Lagopoulos were resolved and consent orders filed. The case proceeded against Dr Gray and Dr Sparks only. I mention this because it casts some light on evidence to which it will be necessary to refer. 4. On 17 May 2017 the primary judge delivered judgment. Although the respondent had framed his case against each doctor on multiple bases, he rejected all but one. He found that both Dr Gray as orthopaedic surgeon, and Dr Sparks as anaesthetist, had breached the duty of care they undoubtedly owed to the respondent by failing to terminate the surgery earlier than they did. He awarded damages quantified at $3,828,075. 5. Dr Gray and Dr Sparks now appeal against the judgment. As there is no Notice of Contention filed on behalf of the respondent, the issues on the appeal are narrow, confined to whether the evidence in the trial permitted the conclusion that either appellant was (or both were) negligent in the treatment afforded to the respondent, by failing to cease the surgery at an earlier time than it was in fact terminated. 6. I have had the advantage of reading in draft the judgment of Macfarlan JA. I agree, for the reasons given by his Honour, that the appeal by Dr Gray should be upheld. Essentially that is because Dr Gray as principal orthopaedic surgeon was entitled to rely on Dr Sparks as principal anaesthetist for advice as to the anaesthetic condition of the respondent, and it was the respondent's anaesthetic condition that dictated the cessation of the surgery. 7. With respect to the appeal by Dr Sparks, I take a different view from that of Macfarlan JA. In my opinion his appeal also should be upheld. 8. In order to explain my conclusions, it is necessary to state, in some detail, the relevant facts. Although I am conscious that this involves some repetition of facts already stated in the judgment of Macfarlan JA, for the convenience of the reader, I will restate those facts and circumstances that have led me to my conclusion. The following account of the relevant facts should be read in conjunction with the account given by Macfarlan JA.

Background facts 1. There is relatively little dispute about the material facts. The following account is drawn from medical records, reports based on medical records, and affidavits and oral evidence of the principal participants and authors of the reports. 2. The respondent, who was born in 1985, suffered a significant genetic disorder (Noonan Syndrome) that caused thoracic lordoscoliosis (which resort to a medical dictionary tells me means forward and lateral curvature of the spine). As a child he underwent a number of surgical procedures. 3. The scoliosis, in turn, caused respiratory lung disease. From about September 2008 the symptoms of the lung disease became progressively worse. In September 2009 the respondent was reviewed by Dr Gray, who held an appointment as a Visiting Medical Officer at RNSH. After investigation and consultation with other medical practitioners, Dr Gray recommended spinal surgery, to be undertaken in two stages. As indicated above, the first stage was performed without mishap on 13 November 2009. It was then anticipated that the second stage would be performed about 10 days later. It was clear that the surgery itself carried risks. Dr Gray explained these to the respondent as early as 18 September; he specifically mentioned "neurological injury including paralysis" as one of the risks of proceeding with the surgery. It was also accepted that the first surgery would have the effect of compromising the blood supply to the respondent's spine and increasing the risk of damage to the spine in the second stage surgery. The second stage of surgery as proposed involved (inter alia) insertion of screws (called "pedicle screws") into the left and right side of the respondent's spine. It was recognised that further risk to the respondent's spine arose by reason of the fact that the second surgery was necessarily conducted with the respondent in the face-down position. These were inevitable features of the surgery proposed and undertaken. Dr Sparks therefore asked Dr Gray to avoid downward pressure on the respondent during the insertion of the pedicle screws. 4. Following the first stage surgery, the respondent was taken to the Intensive Care Unit ("ICU") of RNSH. There his lung condition deteriorated significantly, giving rise to concerns in ICU staff about his prospects of survival. Compression of the left bronchus meant that the left lung could not be oxygenated. On 15 November ICU staff asked that the second stage surgery be expedited, to be performed within 48 hours. It was considered to be clear that further delay would put the respondent's life at risk. 5. Dr Gray agreed to bring the surgery forward and began making plans for that to happen. Those plans included the assembly of a medical and surgical team of experienced practitioners, one of whom was Dr Lagopoulos, a consultant neurophysiologist. Dr Lagopoulos' role was spinal cord monitoring. 6. The purpose of spinal cord monitoring during surgery is to facilitate evaluation of the integrity of the spinal cord and related nervous system, to identify changes in spinal cord function, and thus to allow remedial action to be taken where required. Due to the combination of the perceived urgency of the surgery, and the unavailability of Dr Lagopoulos on 18 November, it was decided that the surgery would be performed on the evening of 17 November. All relevant staff were available on that evening but not the following day. 7. Dr Sparks, who was by reason of his position as Duty Director in charge of theatres for that day, appreciated that the procedure would be challenging and would require an experienced anaesthetist. He volunteered to undertake the task. He agreed to anaesthetise the respondent only because of the perceived urgency of the surgery. He gave oral evidence, that was not challenged, that "in normal circumstances" he would not have agreed to participate, because of the respondent's lung condition. Prior to agreeing to participate, he examined the respondent in order to satisfy himself that the surgery was as urgent and lifesaving as had been represented to him. 8. He enlisted Dr Stephen Barratt, a senior anaesthetist with experience in spinal and thoracic anaesthesia, to assist in performing a bronchoscopy earlier in the day. Dr Sparks discussed the procedure with Dr Barratt, who was therefore familiar with the respondent's case. After that discussion, Dr Sparks decided to use a device called a "double lumen tube", in order to provide oxygen to the respondent's left lung. 9. The respondent was taken to theatre between 6:00pm and 6:10pm on 17 November. (In conformity with the evidence, and with the judgment of Macfarlan JA, I will hereafter use the 24 hour clock.) 10. Notwithstanding the arrangements for Dr Lagopoulos to be present, he was not present when the respondent was taken to the operating theatre. He arrived some time later; the precise time of his arrival is not clear in the evidence. There was a conflict in the evidence as to the position of the respondent when Dr Lagopoulos arrived. It was Dr Lagopoulos' evidence that the respondent was already on the operating table when he arrived. It was Dr Gray's evidence that, when Dr Lagopoulos arrived, the respondent was in a supine (face up) position on the ICU bed, and had not been transferred to the operating table. This issue was not pursued in cross-examination. 11. In any event, on his arrival, Dr Lagopoulos immediately attended to the spinal cord monitoring equipment. From the beginning, the readings given by the monitor were abnormal, and eventually (at about 20:30) disappeared. In the words of Dr Lagopoulos this signified that "there was no conduction down the spinal cord". 12. For the surgery, Dr Sparks was assisted by Dr Andy Wang. Various anaesthetic procedures it is not necessary to detail were undertaken. The operation itself commenced at about 19:30 or 19:40. The respondent was placed in a face down (prone) position. The surgery was expected to be lengthy. From the beginning, the indications that caused Dr Sparks concern continued. He considered that "the emergency nature of the situation" was such that it was necessary to accommodate the adverse indicators. He said in oral evidence that: "A risk of not doing the procedure exceeded the risk of going ahead with the procedure." That remained the position until the respondent's blood pressure and oxygen dropped (at 21:24 or 21:25), at which point: "The risk of proceeding exceeded the risk of not proceeding." 1. The surgery proceeded, but Dr Sparks' concerns did not abate. There were three discrete occasions on which the respondent's blood pressure fell to an abnormally low level (hypotension), and he was showing signs of hypoxia (oxygen deficiency). These occurred at 19:10, 20:35 and 21:25. On the first and second occasions the respondent's condition recovered. The last has been referred to as a "period of circulatory collapse" or a "crash". There had been an earlier (18:50) episode of reduction in oxygen saturation, but this appears to have been transient, caused by the insertion by Dr Sparks of the double lumen tube. 2. In consultation with Dr Wang, Dr Sparks decided: "… that while the arterial blood gas oxygen was normal to high and the blood pressure was normal to high it was reasonable for the surgeons to try and complete the operation" 1. At 20:30 Dr Sparks found it necessary to administer vecuronium, a muscle relaxant. Vecuronium compromises the effectiveness of spinal cord monitoring. Thereafter, any spinal cord monitoring was ineffective. Dr Sparks said: "Because it was emergency surgery I had resolved in my mind that while the oxygenation and blood pressure were normal to high it was appropriate for the surgery to continue." When it became clear that, by the application of those two criteria, it would not be possible for the surgery to complete, he told the surgeons to stop the operation, which they did. That happened at 21:28. 1. Dr Sparks continued to experience concerns and attempted to identify the cause of the respondent's respiratory problems. He formed the view that the cause was cardiac. At about 20:50, by telephone, he consulted two colleagues. One was Dr Barratt, the anaesthetist who was familiar with the respondent's case by reason of his consultation earlier in the day. Dr Barratt was unable to suggest any measures that Dr Sparks had not already taken. There is no evidence that he suggested terminating the surgery. 2. The other colleague Dr Sparks telephoned was Dr David Marshman, a cardiothoracic surgeon, who had assisted Dr Gray in the performance of the first surgery, and was, therefore, also familiar with the respondent's case. 3. The third episode, at 21:25, caused Dr Sparks sufficient concern about the respondent's deteriorating condition that he asked the surgeons to "hurry up". However, within a few minutes, his concerns were such that he feared that the respondent might suffer cardiac arrest. At 21:28 he directed Dr Gray to stop the procedure immediately, a direction with which Dr Gray complied. The surgery ceased at 21:30 and the wound was closed. The respondent was turned to a supine position, where he showed signs of recovery. He was returned to the ICU where his recovery continued. Unfortunately, damage had been done to the spinal cord, causing the respondent's paraplegia. 4. Notwithstanding the injury to the spinal cord, the second stage surgery was completed successfully on 11 December.

The mechanism of the respondent's injury 1. A neurologist, Dr Guy Sawle, identified the cause of the respondent's paraplegia as "a spinal cord stroke" caused by damage to the spinal cord, which, in turn, was caused by oxygen deficiency that resulted in obstruction of circulation. This view was also expressed by others of the experts. A contributing factor to the oxygen deficiency was the first operation, which had had the effect of reducing the number of arteries supplying blood to the spinal cord. (There is no suggestion of negligence in the performance of the first operation. As mentioned above, reduction of the number of arteries was a necessary consequence of the first part of the surgery.) A second factor was "the period of circulatory collapse" during the second operation. Dr Sawle considered that the spinal cord stroke occurred "shortly before" the decision to terminate the operation, at about 21:30, and not during the earlier episodes of low blood pressure and hypoxia. This was said by the primary judge to be uncontroversial.

The case at trial 1. The respondent's claim in negligence was governed by the Civil Liability Act 2002 (NSW) ("the CLA"). The case in contract was particularised in the same way as the case in negligence, and depended upon the same allegations of breach of duty. 2. Although, as set out in the judgment of Macfarlan JA, the primary judge found negligence against Dr Sparks in only one respect (failure to direct the cessation of the surgery at a point earlier than he did), to approach the appeal on that basis only is to mask the way the case was conducted. 3. As finally pleaded against all defendants, multiple particulars of negligence were identified. Notwithstanding the multiplicity of particulars, the case pleaded depended essentially on two allegations: (i) that the commencement of (or the failure to delay) the surgery in the absence of spinal cord monitoring, which was intended to be undertaken by Dr Lagopoulos, or to ensure "complete and effective" spinal cord monitoring was negligent; and (ii) that failure to halt or advise the cessation of the surgery following the adverse signs at various times during the procedure (specified as 18:50, 19:10, 20:35 and 21:20) was negligent. As against Dr Gray, it was also pleaded that the surgery ought not to have been commenced at the time it was, and that there was no necessity for the operation to have been performed as an emergency procedure. As against Dr Sparks, additional particulars asserted: (i) that he had negligently failed to advise Dr Gray that a probable cause of failure of the spinal cord monitoring was the use of the chosen anaesthetics and muscle relaxants and that an alternative which did not affect the monitoring should have been used, and (ii) that he had negligently failed to inform Dr Gray that the likely cause of the respondent's ventilation problems was that he was in a prone position and that this could not be solved in any way other than returning him to a supine position. 1. Both Dr Gray and Dr Sparks denied all allegations of negligence. Dr Gray denied any causal connection between any breach of duty proved against him (relying on s 5D of the CLA), and asserted that he had acted in a manner that was widely accepted in Australia by peer professional opinion as competent professional practice (CLA, s 5 O). Dr Sparks also relied on s 5 O of the CLA, and on s 5 I, which provides that a person is not liable in negligence for harm resulting from the materialisation of an inherent risk. 2. The case presented at trial fluctuated from time to time. At the commencement of the hearing, senior counsel opened with something of a flourish. He said: "Now, the second procedure was brought forward for reasons which have been expressed as dramatically as, 'if we didn't do it, he was going to die', but at its most benign, he was having respiratory difficulties, but respiratory difficulties would be cured, it was hoped, by the second stage; therefore, it was appropriate to bring the surgery forward. At the end of the day, your Honour will conclude that the melodrama was confected, that is to say, it was ex post facto justification for what was done. And the reality was that it was simply convenient." 1. In response to a question from the primary judge, he explained "convenient" as: "… it enabled the surgeon to get all this team together when they were not all available later." He described the decision as "pragmatism". He then described as "a grim irony" that, while the surgery was timed to enable Dr Lagopoulos to be present, he was, in fact, late arriving. 1. By the time senior counsel came to cross-examine Dr Sparks (on the first day of hearing), the position had changed somewhat. Senior counsel commenced his cross-examination by saying: "… it's not part of the plaintiff's case that the commencement of this surgery was not reasonable or not indicated. So, we're not saying the surgery should never have started." 1. During the course of cross-examination he said: "… I accept as my first premise that it was reasonable to commence the surgery. My second premise was though that when it became obvious, as it did, that the surgery was proving to be much more fraught and much more dangerous than it seems you, at least, had assumed, it should have been stopped then. That's what I'm suggesting to you." 1. At the commencement of proceedings the following day, the position changed yet again. Echoing his affidavit evidence, Dr Sparks had given evidence in cross-examination to the effect that if the surgery were elective, he would not have "accepted to take [the respondent] to theatre". Senior counsel said: "… we will submit that the surgery should never have started." He said that the respondent's case was put in the alternative – that the surgery should not have been commenced, and that, if it had, it should have been terminated. 1. Written submissions were produced at the conclusion of the proceedings. In the opening paragraph of the respondent's written submissions, the attack on the decision to bring the surgery forward was again abandoned; it was expressly accepted that the decision to do so was reasonable. The principal submission made in relation to Dr Sparks was: "169 Dr Sparks was negligent in not advising that surgery should have been abandoned at no later than 20:37. He was alive to the patient's metabolic deterioration which would have caused a reasonably competent anaesthetist to call a stop to the surgery."

Medical evidence 1. Apart from Dr Sparks, reports or affidavits were provided by six anaesthetists, five of whom gave oral evidence. 2. As indicated above, until the tenth day of the trial, four defendants were involved. The parties adopted the sensible course of providing the primary judge at the outset with agreed bundles of documents, which included affidavits and expert reports prepared on behalf of the respondent and the defendants (including those defendants who were subsequently released from the proceedings, RNSH and Dr Lagopoulos). That material remained part of the proceedings even after the departure of those two defendants. 3. It is relevant to observe that, as is obvious, the interests of the defendants were divergent, and it was inevitable that, at times, it would suit one defendant to defend his position by shifting the responsibility for certain decisions to another of the defendants. This can most plainly be seen where Dr Gray asserted (correctly in my opinion) that, since the complications that eventually called for cessation of the surgery were related to anaesthetic issues, the principal liability for that decision lay with Dr Sparks. The practical effect of this aspect of the proceedings was that some of the evidence given in Dr Gray's defence bore upon the case against Dr Sparks. 4. The parties also adopted the course of having the medical practitioners retained for the purpose of providing expert opinion meet in conclave and furnish joint reports prior to the hearing. Thus, an anaesthetist who had provided opinion evidence for the respondent (Dr Jon Westbrook) met with an anaesthetist (Dr Paul Forrest) retained by Dr Sparks' solicitors for the purpose of providing opinion evidence. A similar course was taken with respect to orthopaedic experts retained, respectively, by solicitors for the respondent and Dr Gray. The experts then gave their oral evidence concurrently (Dr Westbrook from the United Kingdom). 5. Dr Westbrook is a consultant anaesthetist at the John Radcliffe Hospital in Oxford, UK. He provided a number of reports to the respondent's solicitors, the first dated 10 January 2012. 6. In his reports Dr Westbrook addressed a number of questions. At times, he appeared to question the techniques and instrumentation selected by Dr Sparks. For example, initially Dr Westbrook appeared to query the appropriateness of Dr Sparks' decision to use a double lumen tube, although he later retreated from this position. 7. Relevantly to the present question, whether it was negligent of Dr Sparks not to abandon the surgery earlier, Dr Westbrook said: "Having positioned the patient prone and shown that the endotracheal tube position was not optimal and that the ventilation was difficult and the carbon dioxide level very high a decision could have been taken to abandon surgery at that point … As the decision had already been made to bring forward Mr Hobson['s] surgery because of his deteriorating condition the team may have decided to proceed on that basis." (italics added) 1. Dr Westbrook provided a further report and supplementary report, both dated 21 October 2012. In the earlier of these reports, he said: "The decision to perform Mr Hobson's second operation as an emergency on the evening of 17th November 2009 appears to be critical to this case and the adverse outcome. It meant that the anaesthetists had to persist with an anaesthetic technique that was not achieving optimal gas exchange and ultimately resulted in a significant period of hypoxaemia and hypotension. This appears to have been the cause of Mr Hobson's spinal injury. In addition the operation and the work up to it was commenced before spinal cord monitoring was available. Although it arrived shortly after the start it was not possible to obtain baseline measurements. The monitoring was reported as abnormal throughout the case but this could have been due in part to the anaesthetic difficulties and the use of vecuronium making interpretation very difficult. It is likely that had spinal cord monitoring been properly established in a timely manner that there would have been advanced warning to the clinicians that spinal cord perfusion was threatened particularly during the transient, earlier episodes of hypoxaemia … In the absence of any threat to Mr Hobson's life or spinal cord whilst on the intensive care unit on 17th November 2009 the decision to perform emergency surgery needs to be justified." 1. In the supplementary report of the same date, Dr Westbrook said: "On the balance of probabilities had the surgery been abandoned before the start when the anaesthetic team were already in difficulty Mr Hobson would not have had the problems he had nor suffered his spinal cord injury. There was not sufficient surgical or medical indication to undertake the surgery that night with anything other than optimal ventilation and haemodynamics." 1. In his last report, dated 24 August 2016, Dr Westbrook again addressed the decision to bring the surgery forward, and expressed the view that the assessment of the surgery as "lifesaving" was "erroneous", and that that, in turn, explained the decision to persist despite the adverse signs. He again questioned the decision to expedite the surgery and concluded: "It was the correct decision to abandon the surgery following the episode of severe collapse. There were opportunities earlier in the procedure when the anaesthetic team were struggling to achieve adequate ventilation and oxygenation and effective spinal cord monitoring was not in place for the team to discuss discontinuing the surgery … As previously stated this was a very difficult case given the highly complex surgery in a patient with significant comorbidities and very distorted anatomy causing compression of intra-thoracic structures including the heart and the left main bronchus. Dr Sparks would appear to have persisted with a suboptimal anaesthetic when consideration should have been given to abandoning the procedure. Subsequent statements by Dr Sparks and other members of the medical team suggest that they had assessed the operation to be lifesaving. It is not clear from the notes or Mr Hobson's subsequent progress that this was a correct assessment." (italics added) 1. In a series of reports, Dr Westbrook gradually modified his position with respect to the validity (or otherwise) of the decision to perform the surgery on the evening of 17 November. By the time he gave oral evidence, he considered that, because of the compression of the respondent's bronchus, it was reasonable to commence the surgery when it was commenced. 2. Dr Barratt, the anaesthetist who had assisted Dr Sparks in the bronchoscopy performed on the afternoon of 17 November, and had been consulted by Dr Sparks during the course of the surgery, filed an affidavit on behalf of RNSH. His affidavit was factual, essentially giving an account of the earlier bronchoscopy, and of his conversation with Dr Sparks during the surgery. He did not then express any opinion relevant to the issues raised in the proceedings. He gave the following oral evidence: "Q. Dr Sparks told you that the various metabolic indicators were critical. A. Yes, yes. Q. Despite, apparently, adequate blood pressure and blood oxygen levels. That was one of his dilemmas, wasn't it? A. Yes, yep. Q. Then in those circumstances, it really wasn't appropriate, was it, to look at the blood pressure and blood oxygen levels alone when making a decision whether to persist or abandon surgery? A. I agree with that statement." 1. Dr Wang also provided an affidavit on behalf of RNSH. Dr Wang had assisted the primary anaesthetist (not Dr Sparks) during the first stage surgery. He also assisted Dr Sparks during the second stage procedure. In his affidavit, he gave a factual account of what had occurred during the surgery. He, too, withheld expressing any opinion about the issues in the case. 2. The transcript records the following exchange in cross-examination: "Q. When were there indications to your recollection of when it looked as if he was going to crash? A. Before 9.30. Is it 9.30 when he was about to crash? Blood pressure came down and the saturation came and bradycardia-- Q. What about earlier when Dr Sparks was on the phone to Dr Barrett? There were signs then, weren't there, that he could crash? A. Yes. Q. Did you think at that time, 'We really should be stopping this'? A. I didn't think so at the time. Q. But you were conscious, weren't you, at that time that this is what could happen? HIS HONOUR: Sorry. What could happen? [SENIOR COUNSEL]: That he would crash later. WITNESS: To explain-- [SENIOR COUNSEL] Q. No. I don't want to stop you from explaining but I would like to get an answer to the question which was: at about the time of the Dr Barrett conversation, there were indications, weren't there, that he might well be heading towards a crash? A. There were indications, yes. Q. That was a time, wasn't it, at least when the surgery should have stopped? A. Not necessarily. Q. Not necessarily? Why do you say that? A. Because in my mind the way I perceived the operation, if we don't do the operation he will die. Up until that point, hemodynamically he was still stable. We are drifting – you know, it's difficult but we were managing. He hasn't crashed. If we stopped then, he could die. Q. From what? A. From the reason why we brought him to the operating theatre. Q. All of this proceeds upon an assumption that you had an understanding from somebody else that if the surgery didn't take place then, he would die. Is that correct? A. That's my impression at the time, yes. Q. Your impression? A. Yes, my understanding at the time. Q. So then when he did crash, you say that the anaesthetic team which obviously included yourself-- A. Yes. Q. --and the surgical team together promptly and ultimately made the decision to abandon the operation. Correct? A. Yes." 1. Dr Mike Lambros is a consultant anaesthetist who provided a report to the solicitors acting for Dr Gray. Dr Lambros did not express any opinion about the appropriateness of continuing the surgery to 21:28. 2. Dr Bojidar Manasiev is a specialist anaesthetist who also provided a report to Dr Gray's solicitors, specifically responding to a series of questions put to him by the solicitors representing Dr Gray. In a question numbered 2, Dr Manasiev was asked whether Dr Gray should have advised the halting of the surgery (at any of the times nominated in the particulars outlined above), and if not, to explain his reasons. He gave a lengthy written answer, which included: "… the decision was balanced against the apparent necessity of the operation as a potential lifesaving technique. As such, it was not warranted by Dr Sparks or Dr Gray to halt the surgery at this time and would be considered widely accepted in Australia by peer professional opinion as competent medical practice to continue the surgery." He was also asked whether Dr Gray was negligent in continuing the operation "in the face of the anaesthetic events [described] in the Further Amended Statement of Claim" (those events being the instances of hypoxia and hypotension at 18:50, 19:10 and 21:20). Dr Manasiev replied: "In my opinion, Dr Gray was not negligent in continuing the operation in the circumstances pleaded. As outlined in my answer to 2. above, the management of the ventilatory and cardiovascular parameters is the primary responsibility of the anaesthetist. Dr Sparks' management of the plaintiff in regards to directing Dr Gray to continue the surgery at 18:50, 19:10 and 20:35 and halt the surgery at 21:20 would be considered widely accepted in Australia by peer professional opinion as competent medical practice, with reasoning for each specific time as outlined in question 1 above. As such it would be considered competent medical practice by Dr Gray to heed Dr Sparks' direction and proceed with the surgery at times 18:50, 19:10 and 20:35 and halt the surgery at 21:20." 1. Dr Paul Forrest is the head of Cardiothoracic Anaesthesia and Perfusion at the Royal Prince Alfred Hospital Sydney and a Clinical Associate Professor at Sydney University. He provided a report to Dr Sparks' solicitors dated 26 October 2013. In answer to a specific question, he said that it was "appropriate and reasonable" for Dr Sparks to direct Dr Gray to cease performing surgery at the time he did. In answer to a specific question: "Did Dr Sparks provide a reasonable standard of anaesthetic management to Mr Hobson during surgery on 19 November, 2009?" He replied: "Yes. Mr Hobson was a high risk patient who required major emergency surgery at that time. He posed a very unusual and difficult anaesthetic challenge due to the significant compression of his left main bronchus by his spine and due to the requirement for prone positioning during surgery. … The patient was appropriately monitored during the case, and the choice and dosages of anaesthetic drugs and intravenous fluids were also appropriate. The main clinical dilemma in this case was whether surgery should have been allowed to continue given the difficulties in ventilating the patient that were encountered before the severe deterioration that occurred at 21:30. As noted above, the patient had been difficult to ventilate prior to this time due to compression of his left main bronchus, which was exacerbated in the prone position. However, given that the patient's surgery was considered to be sufficiently urgent that it needed to be performed out of hours, and given also that his lung infection would not have been expected to resolve until the compression of his left main bronchus was relieved by surgery, it was reasonable to continue the anaesthetic at that time." 1. He was also asked: "Did Dr Sparks, in his anaesthetic management of Mr Hobson, act in a manner that was widely accepted in Australia by peer professional opinion as competent professional practice, at the time the service was provided?" to which he answered: "Yes. Mr Hobson was a high risk patient who required major emergency surgery on his spine, in the prone position. … The patient was appropriately monitored intraoperatively, and the anaesthetic drugs, dosages and fluid administration were also appropriate. The management of the patient's critical deterioration at 21:30h was appropriate, as was the decision to abandon the procedure at that time. The anaesthetic management of Mr Hobson by Dr Sparks would therefore have been widely accepted by peer professional opinion in 2009 as competent professional practice." 1. Drs Westbrook and Forrest conferred on 7 September 2016, and provided a joint report in which they addressed a number of specific questions. 2. Dr Westbrook somewhat modified his position concerning the timing of the surgery by saying that it was reasonable, in the light of certain findings, to bring forward the second stage surgery, but added that it did not need to take place on the evening of 17 November, and 24-48 hours would have been a reasonable timeframe. (Dr Forrest was of a different opinion, considering it reasonable to proceed with the surgery that night, given the respondent's respiratory condition.) 3. Dr Westbrook also modified his earlier stated opinion concerning the use of the double lumen tube, which he now considered "not an unreasonable decision". 4. The critical question for present purposes was a question numbered 14. The two anaesthetists had answered the previous question concerning the respondent's blood pressure and decreased oxygen saturation at various times during the surgery and said: "At 21:20, Both experts agree that it is difficult to determine exactly what the cause of the plaintiff's low blood pressure was, but it was likely to have been a combination of patient and surgical factors. At that time, however, his oxygenation was adequate." 1. Question 14 was: "In the light of that indication, what steps, if any, should the anaesthetist have taken, particularly including recommending a cessation of the surgery at any of those times?" The answers were recorded as follows: "Dr Westbrook feels that in view of the significant worsening of the plaintiff's haemodynamic state at 20:35, surgery should have been abandoned no later than 20:37, given the concurrent evidence of his worsening metabolic state as evidenced by blood gas analysis demonstrating a severe acidosis. In Dr Forrest's view, given that the plaintiff's surgery was considered to be potentially lifesaving at that time and was well advanced and also given that the period of haemodynamic instability and desaturation were transient at 20:35, it was reasonable to attempt to continue to improve the plaintiff's ventilation and haemodynamic state. At 21:30, however, it was clearly necessary to abandon surgery given the sudden, severe respiratory and haemodynamic instability that suddenly occurred at that time." 1. The anaesthetists were asked, once the surgery had commenced, when it should have ceased (if at all). The following responses were given: "It is the opinion of Dr Westbrook that the surgery should have been abandoned before 20:37 following the episode of hypotension that occurred at 20:30 hours, coupled with the plaintiff's severe and deteriorating metabolic state that was identified at 20:37 hours (by blood gas analysis). Dr Forrest is of the opinion that the surgery should have been abandoned when the plaintiff suddenly became hypoxic and hypotensive at 21:30 hours." 1. Both experts agreed that the most probable cause of the ultimate spinal injury suffered by the respondent was inadequate supply of oxygenated blood to his spinal cord, and that this most likely occurred at around 21:30. 2. At trial, Drs Westbrook and Forrest gave oral evidence in conclave, Dr Westbrook by video link from London. Dr Westbrook again expressed the view that surgery should have been abandoned "certainly at 20:37". Dr Forrest was more nuanced. He said: "Well, with a benefit of hindsight I think you couldn't argue that would have been preferable to abandon the surgery earlier than – than – than at the time that it was abandoned. That's a retrospective interpretation of the events that the anaesthetist was faced with at the time. You've also got to bear in mind that the key imperative for performing this case out of hours in the first place was that the attending doctors felt that if they didn't operate, his respiratory state would continue to worsen because of the compression of his main stem bronchus. And there was a reasonable expectation, I think, that if surgery had not been successful or not been performed to alleviate that obstruction, that the patient would have died from contractible respiratory failure … … So, I think that there was – would have been a strong sense among the – the – the anaesthetists and attending doctors that – that – that surgery should proceed and that all attempts should be made to correct the underlying causes of his metabolic acidosis, which was being exacerbated by the fact that his ventilation proved so difficult in the prone position. And one thing that was done in order to improve his ventilation was to administer muscle relaxants, which had been withheld up until the period between 20 – 20 – 20.20 and 21.30, in order to attempt to improve his – his ventilation." 1. Three orthopaedic surgeons provided reports. They were Dr Richard Johnson and Dr James Wilson-McDonald, both retained by the respondent's solicitors, and Dr Geoffrey Askin, retained on behalf of Dr Gray. Dr Wilson-McDonald is a consulting orthopaedic surgeon in Oxford, UK. They also conferred and provided a joint report. 2. For the purpose of their report, they were asked: "4 Once commenced, when should the surgery have ceased?" They replied: "The experts agree that cardiorespiratory problems arising in spinal surgery with the patient in the prone position occur infrequently but they have all experienced these problems necessitating the cessation of the operation. The experts agree procedures should have ceased when the anaesthetists were unable to maintain the metabolic state, ie satisfactory blood pressure and oxygenation. Dr Wilson-McDonald notes that at 20:37 blood gas analysis demonstrated a deteriorating metabolic state following an episode of hypotension at 20:30. In his opinion surgery should have been discontinued shortly after this." 1. They were then asked: "18 In the light of (a) the information provided by the anaesthetists or (b) information provided by the spinal cord monitor (upon the assumption that the anaesthetists were informing the orthopaedic surgeon of the difficulties that they were experiencing and the spinal cord monitor was informing the orthopaedic surgeon of the inadequacies or absence of traces on the spinal cord monitoring) should the surgery have been ceased and, if so, when?" The short answer given, representing the opinion of all experts, was: "The experts agree yes, when the anaesthetists reached the stage that they were unable to maintain satisfactory cardiorespiratory parameters." 1. These answers reflect an observation in the report of Dr Johnson to the respondent's solicitors, in which he said: "The decision to halt surgery in the presence of hypoxia and hypotension is anaesthetic rather than surgical matter."

The primary judgment 1. The primary judge found that the decision to advance the second stage of the surgery was "perfectly reasonable" and that the decision to continue the operation "at and beyond 20:30" was also "perfectly reasonable". These conclusions are not challenged. 2. He then found that the absence of any (or any effective) spinal cord monitoring after 20:30 was of no significance, as the administration of the vecuronium to the respondent (which neutralised the effectiveness of the monitoring) was critical and took precedence. He held that, until about 20:35, Drs Gray and Sparks were: "226 … in effect, permissibly taking an expectant approach, in the absence of material that indicated only one possible course of action." 1. He held, however, that that position changed very shortly thereafter. Specifically, he found that both Dr Gray and Dr Sparks were negligent in not taking steps to have the surgery terminated "no later than approximately 21.00". 2. His ultimate conclusions were expressed in six paragraphs. He said: "239 Dr Sparks understood that Mr Hobson's need for surgery was urgent. He examined him and formed that view for himself. Dr Westbrook's opinion that that view was 'erroneous' is necessarily second hand and retrospective. Both Dr Westbrook and Dr Forrest in their joint report expressed the opinion that it was reasonable for the surgery to commence. I am however not satisfied that either Dr Gray or Dr Sparks conformed to the relevant standard of care in failing to halt surgery before 21.25. 240 As I have earlier noted, the orthopaedic surgeons in their joint report indicated that the surgery should have ceased 'when the anaesthetists reached the stage that they were unable to maintain satisfactory cardio respiratory parameters'. The orthopaedic surgeons made no precise reference to a time when the surgery should have ceased. Satisfactory cardio respiratory parameters were not being maintained by 20.30. … 242 It is important not to lose sight of the fact that Dr Sparks and Dr Gray were confronted with what was patently a distressing and fraught intraoperative emergency. It is difficult to over-emphasise just how awful it must have been at that time for all concerned. It is clear that Dr Sparks had attempted all of the anaesthetic manoeuvres in his armoury to correct the problem without apparent success. Criticism of these doctors in those circumstances may seem harsh. However, it is not in question that stopping the surgery when no obvious answer to the problems confronting the doctors was presenting itself would have avoided the damage. We know with hindsight that postural adjustment from prone to supine produced immediate resolution of these problems. That was something which in my opinion Dr Sparks and Dr Gray should have foreseen and acted upon. Failure to do so amounted to a want of reasonable care. It was in my view not appropriate to take the risk that something that could not be explained would or might somehow spontaneously resolve or improve. It is no answer to insist that the surgery was lifesaving in circumstances where Mr Hobson's respiratory difficulties at or after 20.30 had deteriorated below his pre-operative condition in ICU." 1. The primary judge went on to restate his conclusions that the absence of effective spinal cord monitoring after 20:30 did not support a finding of negligence against either of the appellants; he considered that to be "a fact of life in the operating theatre". However, he went on to describe the absence of effective spinal cord monitoring as: "243 … a critically significant factor that not only enlivened, but in fact heightened, the need to act conservatively and to proceed expeditiously. It told against the appropriateness of taking an expectant approach when the solution to Mr Hobson's difficulties had not emerged or was not understood." He then said: "264 Dr Sparks was negligent in not advising that surgery should have been abandoned no later than approximately 21.00. He was alive to Mr Hobson's metabolic deterioration which would have caused a reasonably competent anaesthetist to call a stop to the surgery. Had the surgery been paused or halted at that time, and Mr Hobson turned supine, he would not have suffered spinal cord damage." 1. He restated his conclusion that the absence of spinal cord monitoring was irrelevant, but nevertheless held: "268 … the surgery should have been terminated when it became apparent that no reliable indications of the integrity of Mr Hobson's spinal cord health would be available due to the masking effect of that drug [vecuronium] upon informative traces. I have earlier expressed the view, which I maintain, that the absence of spinal cord monitoring, for whatever reason, should have heightened the doctors' need for caution when proceeding without it." 1. The primary judge then turned to the statutory provisions on which the defendants relied. In his consideration of the defence under s 5 I (the full text of which is set out below, and which provides that a person is not liable in negligence for harm that results from the materialisation of an inherent risk) he acknowledged the judgment of Leeming JA in Paul v Cooke (2013) 85 NSWLR 167; [2013] NSWCA 311 in which his Honour had expressed the view that "if a case can conveniently be decided under s 5 I, it should be", but said that this case could not conveniently be decided under that provision. The primary judge said: "248 … the second stage of Mr Hobson's surgery was not attended by an inherent risk that he might suffer a cardiovascular collapse and vascular disturbance causing lower motor neurone injury, such as his anterior spinal artery syndrome, arising out of the circumstances as they occurred. Mr Hobson had a pre-surgical anatomical vulnerability to spinal cord stroke and the effects of hypotension. However, the damage sustained by Mr Hobson was not the materialisation of a risk that was inherent in undergoing posterior instrumented thoracolumbar surgery having regard to his medical condition at the time. … 251 However, Mr Hobson's paraplegia could in the circumstances have been avoided by the exercise of reasonable care and skill. Neurological injury, including paralysis, was an inherent risk of the surgery. A negligent failure to abandon the surgery, meaning a failure to exercise reasonable care and skill, before his paraplegia developed was not." 1. With respect to s 5 O (the full text of which is also set out below, and which, as mentioned above, provides protection from liability in negligence to a professional who provides professional services in a manner widely accepted in Australia by peer professional opinion as competent professional practice) the primary judge referred to the evidence of Drs Manasiev and Forrest, both of whom had expressed their written opinions in the language of s 5 O. He observed that the respondent had adduced no evidence from any suitably qualified expert contradicting the opinions of those experts, and that no submission on behalf of the respondent had been made with respect to s 5 O. 2. Notwithstanding the absence of any evidence to the contrary of that of Drs Manasiev and Forrest, his Honour rejected their opinions. His reasons for doing so were the same as the reasons for which he had found that Dr Gray and Dr Sparks were in breach of their duty of care to the respondent by failing to halt the surgery earlier than they in fact had.

The grounds of appeal 1. Given my earlier stated concurrence with the view of Macfarlan JA that the appeal by Dr Gray should be upheld, it is only necessary now to address those grounds advanced by Dr Sparks. 2. By Grounds 1 and 2 Dr Sparks complains of the manner in which the primary judge dealt with s 5 O of the CLA. By Ground 3 he complains of the treatment of s 5 I of the CLA. By Grounds 4, 5 and 6 he asserts error in the conclusion that Dr Sparks was negligent in failing to call a halt to the surgery earlier than he did. By Ground 7 he asserts error in some respects in the quantification of the damages awarded.

Applicable legal principles

(i) the common law position 1. Although the respondent's claims in the appeal are governed by the CLA, I proceed on the basis that the common law, as it had been declared prior to the 2002 enactment of the CLA, continues to apply other than as modified by the CLA: Dobler v Halverson (2007) 70 NSWLR 151; [2007] NSWCA 335. Relevantly for present purposes, the common law principle is that "the law imposes on a medical practitioner a duty to exercise reasonable care and skill in the provision of professional advice and treatment" (Rogers v Whitaker (1992) 175 CLR 479 at 483; [1992] HCA 58). The standard imposed is "that of the ordinary skilled person exercising and professing to have that special skill". Whether, in any particular case, there has been departure from that standard such as to render the medical practitioner liable in negligence is a matter for adjudication and determination by the court, although guided by the evidence of medical practitioners skilled in the area of medical practice in question: Rogers v Whitaker, p 487; Rosenberg v Percival (2001) 205 CLR 434; [2001] HCA 18 at [7]. 2. It may be recognised that both Rogers v Whitaker and Rosenberg v Percival were cases in which the issue was alleged failure by the medical practitioner concerned to make appropriate disclosure of risks associated with the treatment proposed. However, it is clear that the principles stated were intended to extend to other aspects of treatment; for example, in Rogers v Whitaker, the High Court said (at 487): "Further, and more importantly, particularly in the field of non-disclosure of risk and the provision of advice and information … it is for the courts to adjudicate on what is the appropriate standard of care after giving weight to 'the paramount consideration that a person is entitled to make his own decisions about his life'." The Court made a distinction between the application of the principle in cases of alleged failure to warn or inform, and cases of alleged negligence in the administration of treatment, saying (at 489): "Whether a medical practitioner carries out a particular form of treatment in accordance with the appropriate standard of care is a question in the resolution of which responsible professional opinion will have an influential, often a decisive, role to play; whether the patient has been given all the relevant information to choose between undergoing and not undergoing the treatment is a question of a different order. Generally speaking, it is not a question the answer to which depends upon medical standards or practices." (italics in original) 1. In Rosenberg v Percival, Gleeson CJ added to the principle already stated, the following: "7 … In many cases, professional practice and opinion will be the primary, and in some cases it may be the only, basis upon which a court may reasonably act. But, in an action brought by a patient, the responsibility for deciding the content of the doctor's duty of care rests with the court, not with his or her professional colleagues." 1. These observations, in my opinion, are particularly pertinent to the present case. It is difficult to imagine how the primary judge (or this Court) could reach a conclusion as to whether Dr Sparks' decision to allow the surgery to continue beyond some unspecified point earlier than 21:00 or 21:15 failed to meet the standard of the ordinary skilled anaesthetist other than as informed by the evidence of witnesses with appropriate expertise.

(ii) the Civil Liability Act 1. The relevant provisions of the CLA are s 5B, s 5 I and s 5 O. All are contained in Pt 1A of the CLA, enacted with effect from 6 December 2002. Section 5B provides as: "5B General principles (1) A person is not negligent in failing to take precautions against a risk of harm unless: (a) the risk was foreseeable (that is, it is a risk of which the person knew or ought to have known), and (b) the risk was not insignificant, and (c) in the circumstances, a reasonable person in the person's position would have taken those precautions. (2) In determining whether a reasonable person would have taken precautions against a risk of harm, the court is to consider the following (amongst other relevant things): (a) the probability that the harm would occur if care were not taken, (b) the likely seriousness of the harm, (c) the burden of taking precautions to avoid the risk of harm, (d) the social utility of the activity that creates the risk of harm." 1. Section 5 O provides as follows: "5O Standard of care for professionals (1) A person practising a profession (a professional) does not incur a liability in negligence arising from the provision of a professional service if it is established that the professional acted in a manner that (at the time the service was provided) was widely accepted in Australia by peer professional opinion as competent professional practice. (2) However, peer professional opinion cannot be relied on for the purposes of this section if the court considers that the opinion is irrational. (3) The fact that there are differing peer professional opinions widely accepted in Australia concerning a matter does not prevent any one or more (or all) of those opinions being relied on for the purposes of this section. (4) Peer professional opinion does not have to be universally accepted to be considered widely accepted." 1. Also relevant to this appeal is s 5 I, invoked by Dr Sparks, which is in the following terms: "5I No liability for materialisation of inherent risk (1) A person is not liable in negligence for harm suffered by another person as a result of the materialisation of an inherent risk. (2) An inherent risk is a risk of something occurring that cannot be avoided by the exercise of reasonable care and skill. (3) This section does not operate to exclude liability in connection with a duty to warn of a risk."

Section 5 I 1. In Paul v Cooke Leeming JA subjected s 5 I to searching scrutiny. The meaning of s 5 I is, to my mind, obscure. Even more obscure is its purpose. It seems to me that it does little (if anything) more than restate that liability in negligence depends upon a causal connection between the negligence alleged and the harm alleged to have been suffered. In that sense, it is a statement of the obvious. What it might achieve is a short cut to a resolution of the issues: if what occurred could not be avoided by the exercise of reasonable care and skill, there is no harm resulting from whatever negligence might be shown to co-exist with or precede the damage suffered, as required by s 5B. This, perhaps, is what Leeming JA meant at [51] of Paul v Cooke, when he said: "51 … the issue of causation, determined in accordance with s 5D, does not arise once it is determined a claim falls within s 5I …" He held that s 5 I provides a complete answer to any claim falling within Pt 1A of the CLA. Leeming JA (with the concurrence of Basten and Ward JJA) considered that, for a s 5 I defence to be made out, what has to be shown to be unavoidable is "the risk of something occurring", as distinct from the occurrence itself. In that case, the surgery proposed and undertaken always carried a risk of the harm that in fact materialised (intra-operative stroke), and that that risk could not have been avoided by the exercise of reasonable care and skill.

Section 5 O 1. In Dobler v Halverson, at [60]-[61], this Court held that s 5 O operates as a defence to a claim, the onus lying on the defendant to establish the relevant facts. In Paul v Cooke, Leeming JA observed that s 5 O, like s 5 I, provides a complete answer to a claim under Pt 1 A of the CLA (at [41]). It is in that sense that the section operates as a defence. For that reason, when it is pleaded, it is convenient to deal with it first. 2. In McKenna v Hunter & New England Local Health District; Simon v Hunter & New England Local Health District (2013) Aust Tort Reports 82-158; [2013] NSWCA 476 this Court held that s 5 O is directed to: "165 … a practice, that was in existence at the relevant time, here July 2004 …", (bold added) and that, in the circumstances of that case, no such practice had been identified. 1. The circumstances that gave rise to the decision in McKenna may be briefly stated. In 2004 a psychiatric patient was discharged by the health authority that administered the psychiatric institution in which he had been compulsorily detained under then applicable mental health legislation. Shortly thereafter, he killed a friend (Stephen Rose) who was transporting him from NSW to Victoria. 2. Members of Mr Rose's family who suffered consequential nervous shock sued the health authority, alleging negligence in the decision to discharge the patient. Their claims also were governed by the CLA. This Court (by majority) held that the health authority owed the plaintiffs a duty of care in accordance with common law principles, which it had failed to discharge. It was therefore necessary to consider the application of s 5 O. It was in that context that the majority construed s 5 O as set out above. On that construction, the defence failed. 3. Macfarlan JA (with whom Beazley P agreed) said: "165 … It is unlikely, to say the least, that there would have occurred in or before 2004 a number of situations in which there were sufficient features in common with the present case to enable it to be said that there was a practice concerning how such a situation was to be dealt with by a competent medical practitioner." (bold added) 1. An appeal to the High Court of Australia was successful on the ground that this Court erred in finding that the health authority owed the plaintiffs a duty of care; the High Court therefore did not find it necessary to address the construction of s 5 O: Hunter and New England Local Health District v McKenna; Hunter and New England Local Health District v Simon (2014) 253 CLR 270; [2014] HCA 44. 2. I consider that I am obliged to accept McKenna (in this Court) as stating the prevailing construction of s 5 O: Gett v Tabet (2009) 254 ALR 504; [2009] NSWCA 76 at [277]-[279]. But for that constraint, I would have considered that the language of s 5 O makes it plain that "competent professional [here, medical] practice" is intended to denote "the practice of a profession [here, medicine]", and not a specific practice or method of providing the professional services in question. That construction is supported by the absence of the indefinite article in conjunction with "professional practice", and the use instead of the adjective "competent", which to my mind signifies professional practice in a general sense, rather than an identifiable, specific, and discrete aspect of the profession or method of providing the professional service. 3. As construed in McKenna, s 5 O can apply only in limited circumstances, where the defendant can, or seeks to, identify a discrete practice to which he or she conformed. It necessarily excludes unusual factual circumstances, such as occurred in McKenna, and such as occurred in the present case. It does not appear to me that s 5 O was intended to have such limited application. However, as I have said, I consider myself constrained to follow and apply that decision. 4. Failure by a defendant to prove the s 5 O circumstances (however that section is construed) does not conclude the matter. The onus remains on the plaintiff to establish that the defendant failed to provide the professional service in accordance with the standard of the ordinary skilled person practising that profession. 5. The claim is then to be determined by reference to s 5B of the CLA: see Adeels Palace Pty Ltd v Moubarak; Adeels Palace Pty Ltd v Bou Najem (2009) 239 CLR 420; [2009] HCA 48 at [27]. The relevant questions are: * was there a foreseeable risk of harm arising from the conduct the subject of the claim?; * was the risk not insignificant?; * would a reasonable person in the position of the defendant have taken precautions to safeguard against the risk? (It is necessary for the plaintiff to identify the precautions it is alleged ought to have been taken.)

Determination 1. With those legal principles in mind, I turn to the determination of the issues raised on the appeal. 2. In seeking to apply the principles to the present case, it is worth restating, briefly, the relevant chronology. Surgery commenced at about 19:10 or 19:15. At 19:10 and 20:35 the respondent's blood pressure dropped, but recovered. There were identifiable causes of these episodes – the insertion of the double lumen tube and the insertion of the pedicle screws. At about 20:50 Dr Sparks was sufficiently concerned by the respondent's condition to consult two colleagues, one an anaesthetist and one a cardiac surgeon. At about 21:24 the respondent's blood pressure again dropped, causing Dr Sparks to direct cessation of the surgery. 3. The conclusion of the primary judge was that the decision to continue beyond 20:30 was "perfectly reasonable", but that Dr Sparks ought to have directed that the surgery cease at some time before 21:00 or 21:25. It was only in his consideration of causation, with which he dealt appropriately briefly, that the primary judge nominated 21:15 (at the latest) as the time by which surgery should have ceased. He did this in the context of noting that it was uncontroversial that the paraplegia was caused at some time after 21:15 and before 21:30.

Grounds 1 and 2: section 5 O 1. The construction given to s 5 O in McKenna played no part in the primary judge's rejection of the defences under that section. No ground of appeal sought to call in question the correctness of the McKenna construction of s 5 O. However, if, under s 75A of the Supreme Court Act 1970 (NSW), the court were to proceed to its own consideration of the s 5 O issue, it would be necessary to determine what construction to adopt. 2. Senior counsel for Dr Sparks did suggest, during oral argument, that this Court declare that the McKenna construction is wrong. In the absence of any advance notice of that proposal, and any request for the constitution of an enlarged Bench, the suggestion must be rejected. 3. Were the construction of s 5 O that I prefer to prevail, I would uphold these grounds of appeal. Drs Manasiev and Forrest were unequivocal in their evidence that Dr Sparks acted in a manner that at the time was widely accepted in Australia by peer professional opinion as competent professional practice. No countervailing evidence was given on behalf of the respondent. Indeed, it is difficult to see how Dr Westbrook (the respondent's only expert anaesthetist witness) could comment on peer professional opinion in Australia. He practises in the United Kingdom, and gave evidence from London. There was no evidence that he has any Australian experience. 4. Whether Dr Sparks acted in accordance with widely accepted peer professional practice is a question of fact; it is not a question of the kind referred to in Rogers v Whitaker and Rosenberg v Percival, involving determination of whether a medical practitioner failed to conform to standards of the ordinary skilled medical practitioner (in this case, practising as an anaesthetist). Under s 5 O, the task of the court is not to evaluate the merits of the competing views (if there is evidence of competing views) but to determine whether, as a factual matter, the service had the acceptance of peer opinion, even if other peer opinion was different. 5. However, adopting as I consider I must, the McKenna construction of s 5 O, and since, principally because the circumstances of this case were highly unusual, it was not possible for Dr Sparks to identify "a practice" to which he conformed, the s 5 O defence must fail. That is notwithstanding that the overwhelming medical evidence was that his conduct was in accordance with what was widely accepted in Australia as "competent professional practice".

Ground 3: section 5 I 1. Dr Gray's September advice to the respondent makes it plain that there was always a risk that the surgery would result in neurological injury, including paralysis. It is also clear from Dr Sparks' reluctant agreement to participate in the operation that significant risks were involved. Although Dr Sparks did not expressly spell out what those risks were, it is a reasonable inference on the whole of the evidence that they included the very thing that happened. 2. Whether the risk of neurological injury including paralysis was an "inherent risk" for the purposes of s 5 I depends upon whether that risk could have been avoided, by the exercise of reasonable care and skill. Having regard to the primary judge's finding that Dr Sparks was in breach of his duty of care in failing to terminate the surgery earlier than he did, the finding that, by the exercise of reasonable care and skill, the harm suffered by the respondent could have been avoided was logical and inevitable. 3. On behalf of Dr Sparks it was argued that, as in Paul v Cooke, the primary judge erroneously focused on the potential for Dr Sparks to avoid the occurrence rather than risk of the occurrence. True it is that the risk could have been avoided by a decision not to operate at all. That, in the circumstances of the respondent's condition, was not a realistic proposition. Once it is accepted that the respondent's condition warranted the performance of the operation as emergency surgery, and that that surgery carried a risk of paraplegia, it seems to me that this is a rare case, like Paul v Cooke, in which s 5 I applies. I would uphold Ground 3.

Grounds 4, 5 and 6: breach of duty 1. Since satisfaction of the s 5 I criteria is a complete answer to the claim it may be unnecessary to address the remaining grounds. However, even if I am wrong about s 5 I, I have concluded that the evidence does not support the conclusion that Dr Sparks failed in his duty to exercise the skill and care required of a specialist anaesthetist by failing to take steps to ensure that the operation was terminated at any earlier stage than he did. In the present case, the answers to the first and second questions that arise under s 5B are obvious. There was a risk of harm to the respondent from the administration of anaesthesia given his respiratory condition. That risk was both foreseeable and foreseen. The risk was far from insignificant. The issue is whether Dr Sparks ought to have taken precautions against the risk, those precautions being the termination of the surgery at not later than 21:00 or 21:15. That question is to be decided by reference to the four factors set out in sub-s (2) (as well as any other "relevant thing"). In a case of alleged professional negligence "other relevant things" must include the opinions of relevant experts, as envisaged in both Rogers v Whitaker and Rosenberg v Percival as to conformity (or otherwise) with relevant standards. 2. In the light of the rather lengthy exposition of the facts above, the reasons for my conclusion that the evidence did not establish any breach of his duty of care on the part of Dr Sparks may be stated with relative brevity. 3. The central circumstance to note is the parlous condition in which Dr Sparks reasonably understood the respondent to be, pre-surgery. The medical consensus, as at 17 November, was that the respondent needed urgent surgery to ensure his survival. Although Dr Westbrook at one point challenged that view, Dr Sparks' conduct must be assessed in the light of what he had been told by other respected medical practitioners and in the unchallenged finding of the primary judge that the decision to undertake the surgery when it was undertaken was "perfectly reasonable". It was the ICU staff who first drew attention to the respondent's life threatening condition. Dr Sparks was entitled (and probably obliged) to act upon the fears of those experienced medical practitioners, or at least to take them into account. Indeed, as I have noted above, his evidence was that, were the surgery not as urgent as he understood it to be, he would not have anaesthetised a patient in the condition of the respondent. That circumstance permeated his decision-making throughout the entire process, during which he was faced with the unenviable task of balancing two competing, extremely serious, risks: on the one hand, the risk that without the surgery the respondent's survival was in doubt; on the other, the risk that the surgery itself threatened his survival. Initially, on Dr Sparks' assessment, the former outweighed the latter. When he perceived that the balance had changed, he acted appropriately to have the surgery halted. There is no evidence to support a proposition that his assessment in this respect was erroneous, let alone negligently erroneous. 4. Not one of the anaesthetists who reported and gave evidence expressed a view that Dr Sparks' conduct failed to reach the relevant standard. The nearest was that of Dr Westbrook who considered that the surgery should have stopped at 20:37. Even so, Dr Westbrook's opinion was given at a time when he rejected the otherwise generally accepted opinion that the surgery was necessary to ameliorate a life threatening condition. His conclusion about the time at which it should have ceased is coloured by that, now known to be mistaken, view. Moreover, as the passage extracted above at [286] demonstrates, he based the assessment, at least in part, on "[the respondent's] subsequent progress" – that is, on events that post-dated the decision of Dr Sparks – which nobody suggested was or should have been apparent at the time. 5. It is not now in issue that the surgery was reasonably believed to be urgent and lifesaving. The concerns of the ICU staff were expressed to Dr Gray and passed on by him to Dr Sparks. Dr Sparks independently satisfied himself of that circumstance. It was also recognised that the surgery was of a complexity that called for the assembly of a particularly skilled and experienced team of specialists, including the neurophysiologist Dr Lagopoulos. The degree of urgency, together with the need for specialised assistance, may be gauged by the fact that the operation was scheduled to take place out of ordinary operating hours. Further, it cannot be overlooked that Dr Sparks agreed to undertake the anaesthetic role only because of the perceived urgency. His evidence that, absent that urgency, he would not have agreed to anaesthetise the respondent is a further indicator of the dire situation in which the respondent was perceived to be. There is nothing in the evidence that supports doubt about that perception. That also influenced his decision to persist, and his reliance on the two most salient factors, the respondent's blood pressure and oxygenation. 6. In this regard, reliance on subsequent events (the respondent's recovery, and the ultimate successful performance of the second stage surgery, on 11 December) provides no answer: see Moubarak at [31]. Dr Sparks, and the entire medical team, had to work on what they knew at the time, which was that the respondent's condition was life threatening. The finding (in [242]) that Dr Sparks and Dr Gray ought to have foreseen that "postural adjustment" from a prone to a supine position would have produced immediate resolution of the respondent's respiratory problems, and acted on that anticipation, was largely based on what happened after the surgery had terminated and is not sustainable in the light of what is known of the respondent's pre-surgery condition. It does not take into account the extraordinarily painful risk-balancing exercise in which Dr Sparks had to (and did) engage. 7. On behalf of the respondent, specific reliance was placed on the earlier episodes of hypotension and hypoxia as indicating that the surgery should have ceased earlier than it did. Two responses may be made to this. The first is that each episode was explicable by a specific event – the insertion of the double lumen tube, and then pressure being placed on the respondent by the insertion of "pedicle screws". On each occasion, when the cause of the deterioration was removed, the respondent's condition improved. The second answer is that there was no evidence that the pre-existing condition of the respondent (the condition that compelled the expedition of the surgery) had diminished. That it did on his return to the ICU says nothing about what the signs were at the time. 8. Reliance was also placed on behalf of the respondent on an answer given by Dr Barratt in cross-examination, extracted above. This was directed to Dr Sparks' evidence that, in determining to permit the surgery to proceed, he had relied principally on the respondent's blood pressure and blood oxygenation levels: Dr Barratt was asked: "Then in those circumstances, it really wasn't appropriate, was it, to look at the blood pressure and blood oxygen levels alone when making a decision whether to persist or abandon surgery?" He agreed with the proposition contained in the question. The primary judge regarded this answer as "critical". Dr Barratt replied that he agreed with that statement. Again, two answers may be given to the proposition. The first is that other specialist medical evidence was more favourable to Dr Sparks: Dr Forrest, asked a similar question in oral evidence, answered: "Well, these are the parameters that are – that are used routinely in anaesthetic practice to – to guide our management and they're not the only factors that would determine how the surgery would be conducted. But in this particular case, they would be the – the main factors that would be used to determine whether surgery should continue or not." 1. Dr Westbrook, giving evidence concurrently with Dr Forrest, did not dissent from that answer. He had earlier said that blood gas analysis showed evidence of other serious and deteriorating problems, but agreed that those problems were reversible. 2. Dr Manasiev was asked in cross-examination what factors would inform competent professional practice with respect to anaesthetists and the continuance or otherwise of surgery. The transcript records the following answer: "Well, it's the whole gambit [sic – gamut] of all the haemodynamic parameters that you're looking at within a patient. Predominantly, the blood pressure and saturation, which are telling you how the organs are being perfused, but as well as that, all the attempts that are made, in this case, to improve ventilation … it's a complicated gambit [sic – gamut] of numbers and figures that you're looking at." Ultimately, he said: "You wouldn't exclude, but you would give different parameters different weights upon the patient's stability." 1. The second answer to the proposition is that the evidence did not extend to precise identification of what other factors ought to have been considered. More importantly, no conclusion can, on the evidence, be drawn as to what decision would, on the probabilities, have been made in the light of the other considerations. In other words, there is no evident causal connection between Dr Sparks' reliance on those two factors (to the possible exclusion of others) and the injury suffered by the respondent. 2. It has been suggested that, urgent as the surgery may have been, it was not so urgent that the respondent would have died if it were not completed within a few hours. This must be seen in the light of acceptance on behalf of the respondent (and the unchallenged finding of the primary judge) that it was reasonable to undertake the surgery at the time it was commenced, and in the circumstances in which it was commenced. A decision to terminate surgery only partly completed, after anaesthetisation of the patient, is very far from a decision to commence, or not to commence, surgery. It was not, I am satisfied, demonstrated that it was outside the bounds of proper practice for Dr Sparks to persist in his efforts to maintain the respondent's stability in order to allow the operation to proceed to conclusion. 3. The medical evidence does not, in my opinion, support a finding that, in failing to direct the termination of the surgery before 21:28, Dr Sparks failed to exercise reasonable care and skill. The decision Dr Sparks had to make (on a continuing basis throughout the surgery) involved the exercise of clinical judgment. Although, as decided by Rogers v Whitaker, the ultimate determination as to whether the clinical judgment made came within the bounds of the exercise of reasonable care and skill expected of a competent anaesthetist lies with the court, the judgment is one which must, in this case, be guided by the evidence of other medical practitioners with the requisite knowledge and understanding of the issues involved. So much is clear from Rosenberg v Percival, and, indeed, from Rogers v Whitaker. It was not sufficient to say, although it is plainly the case, that, had Dr Sparks directed termination of the surgery prior to the respondent's collapse at 21:28, the injury would not have occurred. The respondent bore the onus of establishing that Dr Sparks' decision not to direct the termination of the surgery before that time represented a departure from the standard of care and skill required of a specialist anaesthetist. That onus was not discharged. The medical evidence falls well short of permitting a conclusion to that effect. 4. Dr Westbrook's opinion that a decision "could have been taken to abandon surgery" earlier than it was abandoned is insufficient to establish that failure to make that decision lay outside the bounds of competent anaesthetic practice. For the purposes of Dr Sparks' appeal, the evidence of the orthopaedic surgeons that the surgery should have been brought to an end "when the anaesthetists were unable to maintain the metabolic state, ie satisfactory blood pressure and oxygenation" or "when the anaesthetists reached the stated that they were unable to maintain satisfactory cardiorespiratory parameters" can be given little (or no) weight. The true import of that evidence, in the context in which it was given, was that Dr Gray was entitled to rely on the advice given to him by Dr Sparks and that the decision lay within the anaesthetic (not orthopaedic) speciality. The answer given carefully (and properly) avoided the expression of opinion by orthopaedic specialists in respect of an anaesthetic issue. 5. It follows that, in my opinion, the primary judge was in error in finding breach of duty on the part of Dr Sparks. I would uphold the appeal and set aside the judgment.

Damages 1. It follows that, in my view, it is unnecessary to determine the appeal so far as it relates to the quantification of damages. It is sufficient to record that, if it were necessary to decide those issues, I would agree with the judgment of Macfarlan JA. 2. The orders I would make are: (1) The appeal by Dr Gray is upheld. (2) The appeal by Dr Sparks is upheld. (3) The judgment against each defendant is set aside. (4) The respondent is to pay the costs of each appellant of both the trial and the appeal. (5) The respondent be granted a certificate under the Suitors' Fund Act 1951 (NSW).

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Endnotes 1. Hobson v Northern Sydney Local Health District [2017] NSWSC 589 ("Hobson"). 2. The judge upheld one, saying there were 15, which is not clear from the pleading: Hobson at [6]. 3. Defence to third amended statement of claim (Dr Gray), 14 November 2016, par 40. 4. Amended defence (Dr Sparks), 10 November 2016, par 23. 5. Fourth Defendant's outline of submissions, 21 November 2016, pars 124-140 (Dr Sparks); Second Defendant's outline of submissions, 22 November 2016, pars 195-202. 6. Dobler v Haloverson (2007) 70 NSWLR 151; [2007] NSWCA 335 at [60] (Giles JA); Sydney South West Area Health Service v MD [2009] NSWCA 343; (2009) 260 ALR 702 at [21]-[25] (Hodgson JA), [51] (Allsop P), [58] (Sackville AJA). 7. Interpretation Act 1987 (NSW), s 35(2)(a). 8. Dobler at [61]. 9. Dobler at [55]. 10. (1992) 175 CLR 479 at 487; [1992] HCA 58 (citations omitted). 11. Cf now Montgomery v Lanarkshire Health Board [2015] 1 AC 1430. 12. [1957] 1 WLR 582 at 587. 13. [1985] AC 871 at 881. 14. Sidaway at 876. 15. (2001) 205 CLR 434; [2001] HCA 18 at [7]. 16. Naxakis v Western General Hospital (1999) 197 CLR 269; [1999] HCA 22 at [21] (Gaudron J), [47] (McHugh J), [81] (Kirby J). 17. Dobler at [61]. 18. Cf Qidwai v Brown [1984] 1 NSWLR 100 at 102, dealing with misconduct of a medical practitioner in a professional respect. 19. McKenna v New England & Hunter Local Health District [2013] NSWCA 476; (2013) Aust Torts Rep 82-158 ("McKenna"). 20. McKenna at [160] (emphasis in original). 21. Hunter and New England Local Health District v McKenna (2014) 253 CLR 270; [2014] HCA 44 ("Hunter Health District"). 22. (1998) 194 CLR 395; [1998] HCA 48 at [56]. 23. (1981) 146 CLR 336 at 410; [1981] HCA 4. 24. [2011] NSWCA 59 at [3] (Beazley and Tobias JJA agreeing). 25. Hunter Health District at [12]. 26. See CEMEX Australia Pty Ltd v Takeovers Panel (2009) 177 FCR 98; [2009] FCAFC 78 at [94]-[95] (Ryan, Jacobson and Foster JJ). 27. (2013) 85 NSWLR 167; [2013] NSWCA 311. 28. Civil Liability Act, s 5I(3). 29. Paul v Cooke at [80]. 30. Hobson at [196]. 31. Hobson at [38], par 7 of Dr Westbrook's supplemental report of 21 October 2012. 32. Hobson at [39]. 33. Hobson at [59]. 34. Hobson at [224]. 35. Affidavit of Stephen Barratt, 12 November 2015, at Hobson [57]. 36. Hobson at [226] (italics added). 37. Hobson at [240]. 38. Tcpt, 14/11/16, p 264(27). 39. Tcpt, p 265(24). 40. Tcpt, p 265(50). 41. Tcpt, 08/11/16, pp 103-104 42. Hobson at [242]. 43. Fourth defendant's outline of submissions, 21 November 2016, par 133. 44. Hobson at [259]. 45. Report of Dr Forrest, 26 October 2013, pp 5-6. 46. Report, pp 3-4. 47. Report, p 5. 48. Tcpt, 14/11/16, p 268(33). 49. Report of Dr Manasiev, 26 October 2016, p 3. 50. Report, p 3. 51. Report, p 4. 52. Tcpt, 14/11/16, p 294(28). 53. Hobson at [122]. 54. Hobson at [248] and see [249(2)]. 55. Report of Joint Orthopaedic Expert Teleconference Conclave of Drs Johnson, Askin and Wilson-MacDonald, 7 October 2016, p 6. 56. Affidavit, Randolph Gray, 7 November 2016, p 5. 57. Tcpt, 07/11/16, p 40(15). 58. Report, p 4. 59. Tcpt, 14/11/16, p 295(5).

Amendments 14 May 2018 - [214]: Formatting correction. DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated. Decision last updated: 14 May 2018