Medical negligence (Warfarin Care Service) – duty of care to give advice

 Papa v Sullivan Nicolaides Pty Ltd [2010] QSC 364

CATCHWORDS: PROFESSIONS AND TRADES – HEALTH CARE PROFESSIONALS – MEDICAL PRACTITIONERS – LIABILITY IN TORT – DUTY TO WARN OF RISKS – where the plaintiff patient had a mechanical heart valve – where as a consequence of this the plaintiff had to take anti-coagulant medication, Warfarin, for the rest of her life – where the levels of Warfarin in the blood needed to be monitored to ensure they remained within an appropriate range – where there were serious risks of blood clots and stroke when the levels of Warfarin dropped below the target range – where there were serious risks of bleeding when the levels of Warfarin were above the target range – where the defendant firm of specialist medical pathologists monitored the plaintiff – where the plaintiff had five blood tests within 12 days showing her Warfarin level was below the target range – where the defendant advised the plaintiff and her general practitioner that they would no longer be monitoring her Warfarin levels – where the defendant did not tell the plaintiff, her general practitioner or her cardiologist that her Warfarin levels were below the target range – where the plaintiff suffered a stroke – whether the defendant breached its duty of care to the plaintiff

 

Issues:

The matter was heard on 20 April 2009 – 24 April 2009, however, judgment was reserved pending the determination of the High Court appeal in Tabet v Gett [2010] HCA 12 (21 April 2010). The plaintiff had claimed in the alternative having suffered a lost chance or opportunity of receiving reasonable and appropriate treatment, which would have eliminated or reduced the prospects of suffering a stroke. Given the High Court decision which was delivered after the trial, such a claim was no longer available.

I refer you to my earlier posting in this respect.

Accordingly, the matter proceeded on the basis of two alternatives:

  • Whether defendant failed to exercise and observe the standards of a reasonable Warfarin care haematologist in the management of the plaintiff’s Warfarin dosage levels in the period 13 – 27 February 2002; and
  • Whether, according to the relevant professional and practicing standards at the time, the defendant, when presented with this artificial mitral valve patient with a recent history of INR instability and persistent sub-therapeutic INR’s, ought to have given advice to the plaintiff, her GP or her cardiologist, and if so, what the content of that advice ought to have been and when it ought to have been given.

The first question was resolved in the defendant’s favour [156], however, the second in favour of the plaintiff [177].

Quantum was in dispute, most notably lost earning capacity, gratuitous care and Wilson v McLeay damages.

The facts:

[1] The plaintiff, who was born on 28 May 1956, suffered from mitral incompetence, i.e. a leaking valve between the left atrium and left ventricle in her heart. On 11 July 2001, she underwent surgery for this condition by a procedure known as a mitral valve replacement, in which an artificial mechanical valve was inserted in her heart.

[2] A consequence of the insertion of this mechanical valve was that it became necessary for the plaintiff to take anti-coagulant medication for the rest of her life to assist in preventing the formation of clots around the valve or in the heart. Her cardiac surgeon prescribed the anti-coagulant, Warfarin.

[3] The levels of Warfarin in a patient’s blood need to be monitored in order to ascertain whether they are within an appropriate therapeutic range and the dosages of Warfarin need to be adjusted in order to keep the Warfarin level within that range.

[4] The defendant is a firm of specialist medical pathologists. One of the services it has offered since 1999 is the Warfarin Care Service (“WCS”). The WCS takes samples of patients’ blood and analyses them for the current Warfarin level. The patient is then advised by the WCS as to the dosage of Warfarin which he or she is to take until the next test and is also told when the next test is to be.

[5] In the period from 13-25 February 2002, the plaintiff had five blood tests with the WCS, each of which showed that her Warfarin level was “sub-therapeutic”, i.e. below the target range of anti-coagulation. This meant that the plaintiff was at an increased risk of developing clots.

[6] On 27 February 2002, the defendant advised the plaintiff and her general practitioner, Dr Powell, that the defendant would no longer be monitoring the plaintiff’s Warfarin levels and that she was, in effect, removed from the WCS. (The reasons for the defendant taking that step are no longer in issue on the pleadings.)

[7] On 28 February 2002, Dr Powell saw the plaintiff, and referred her to the Warfarin monitoring service run by another firm of pathologists, Queensland Medical Laboratories (“QML”).

[8] On 1 March 2002, the plaintiff suffered a stroke (described as a “large right middle cerebral artery territory embolic infarction”), which was caused by an embolism, i.e. a blood clot.

His Honour Daubney J considered in detail the Warfarin Care Service, medical, specialist and other evidence, which is peculiar to this claim and lengthy and applied Rogers v Whitaker and Rosenberg v Percival.

Duty of care

 [78] In Rogers v Whitaker[3] the majority of the High Court authoritatively stated the duty of care owed by a medical practitioner in the following terms:[4]

“The law imposes on a medical practitioner a duty to exercise reasonable care and skill in the provision of professional advice and treatment. That duty is a ‘single comprehensive duty covering all the ways in which a doctor is called upon to exercise his skill and judgment’; it extends to the examination, diagnosis and treatment of the patient and to the provision of information in an appropriate case. It is of course necessary to give content to the duty in the given case.

The standard of reasonable care and skill required is that of the ordinary skilled person exercising and professing to have that special skill …”

[79] In determining the standard of care required to observe the duty, the majority said:[5]

“The duty of a medical practitioner to exercise reasonable care and skill in the provision of professional advice and treatment is a single comprehensive duty. However, the factors according to which a court determines whether a medical practitioner is in breach of the requisite standard of care will vary according to whether it is a case involving diagnosis, treatment or the provision of information or advice; the different cases raise varying difficulties which require consideration of different factors. Examination of the nature of a doctor-patient relationship compels this conclusion. There is a fundamental difference between, on the one hand, diagnosis and treatment and, on the other hand, the provision of advice or information to a patient. In diagnosis and treatment, the patient’s contribution is limited to the narration of symptoms and relevant history; the medical practitioner provides diagnosis and treatment according to his or level of skill. … 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 …”

[80] As was subsequently made clear in Rosenberg v Percival[6] reference by the Court to evidence of professional practice and opinion will be relevant, but not conclusive, in respect of the Court’s determination of the content of the duty owed by a treating doctor and the steps required to meet that duty.[7]

[81] It is also important to remember that one must adopt a prospective, and not a retrospective, perspective when enquiring into these matters. The resolution of the question as to whether there was breach of duty “is not to be undertaken by looking back at what has in fact happened, but by looking forward from a time before the occurrence of the injury giving rise to the claim”.[8]

 Conclusions on Liability

[151] Numerous articles from learned medical journals were put before me. Some of these were relied on by various of the experts to support their opinions. Others were used as the basis for cross-examination. Some of the articles refer to research and learning after 2002. These articles assisted me in understanding the evidence of the experts and also, to some degree, support the evidence given as to the state of knowledge in the realm of anti-coagulant control as at 2002.

[152] It seems to me that the following propositions relevant to Warfarin control by specialist Warfarin care haematologists in 2002 can be drawn from the expert evidence:

(a) that the Warfarin dosage management process necessarily involved a balancing of the risk of under anti-coagulation and over anti-coagulation;

(b) that there was a known risk of thromboembolic event in the case of sub-therapeutic INR levels, and that this risk magnified when the INR was at or below 1.5;

(c) that there was a known risk of haemorrhagic event in the case of supra-therapeutic INR levels, and that this risk magnified very significantly when the INR was at or above 6.5;

(d) that in relative terms, the risk of an haemorrhagic event at INR 6.5 or higher was significantly greater than the risk of thromboembolic event at INR 1.5 or less;

(e) that the process of Warfarin dosage management with a view to keeping the INR within target range, and thereby minimising these risks, necessarily involved a significant component of clinical judgment on the part of the Warfarin care haematologist;

(f) that it was accepted practice at the time that the anti-coagulants Clexane or Heparin could be used on a patient with an artificial mitral valve as “bridging therapy” by way of a substitute for, or supplement to, Warfarin in a peri-operative setting;

(g) that neither the medical literature then available nor the standards of practice among Warfarin care haematologists at the time support a conclusion that it was appropriate for a Warfarin care haematologist, when dosing a patient with an artificial mitral valve who had a persistent sub-therapeutic INR, to supplement the prescription of Warfarin with either:

(i) the administration of Clexane or Heparin, or

(ii) the administration of “stat” doses or Warfarin.

[153] In making these findings, I do not reject the evidence of either Professor Fox or Dr Davidson as to what their own particular practices were. But it was quite clear, in my view, on both the evidence as a whole and on their own evidence that there was not widespread support either amongst the haematologists or in the literature for the notions that a Warfarin care haematologist treating an artificial mitral valve patient with persistent sub-therapeutic INR ought to have resorted to the other anti-coagulants or “stat” doses. On the contrary, the general consensus amongst the experts was that the cautious approach of incremental increases in the Warfarin doses was appropriate.

[154] The conduct of the defendant in this case needs to be assessed not just in the context of the period in late February 2002, when the plaintiff was returning persistently low INR’s. It was clearly appropriate for the haematologist also to have regard to the fact that in the preceeding month the plaintiff’s INR had on two occasions “spiked” on the administration of average daily doses of 3.17mg of Warfarin to levels at which the risk of haemorrhagic event became significantly elevated (that being, in relative terms, the greater of the two risks in the balance). This was, as was conceded by a number of the experts, a difficult situation for the Warfarin care haematologist to manage. Reference by the haematologist to the immediate past history of “spiking” supported the cautious approach of incrementally increasing the dosages of Warfarin in an attempt to bring the plaintiff’s INR above the sub-therapeutic level and into the target range.

[155] I do not regard Dr Garrahy’s evidence as to the treatment he would have administered as particularly relevant to the present question. What treatment a cardiologist would have administered does not address the appropriate conduct of a Warfarin care haematologist.

[156] Accordingly, I would not be prepared to find that it has been established that the defendant failed to exercise and observe the standards of a reasonable Warfarin care haematologist in the management of the plaintiff’s Warfarin dosage levels in the period 13 – 27 February 2002.

[157] The separate question on liability is, however, quite different. It goes to whether, according to the relevant professional and practicing standards at the time, the defendant, when presented with this artificial mitral valve patient with a recent history of INR instability and persistent sub-therapeutic INR’s, ought to have given advice to the plaintiff, her GP or her cardiologist, and if so, what the content of that advice ought to have been and when it ought to have been given.

[158] It is quite clear, on the facts of this case, that the defendant in fact gave no advice to the plaintiff or her medical practitioners until, at best, Dr Rowbotham’s call to

Dr Powell on 27 February 2002. The only information being provided to the plaintiff were her dosage instructions and the dates for her next tests. She was not routinely advised of her actual INR levels. I find that she was not so advised by the defendant’s phone representative during January and February 2002.

[159] The information package initially provided to the plaintiff stated, inter alia:

“The target range is set either by your doctor according to your individual circumstances or by internationally recommended ranges for your condition. The target range defines acceptable results for you. Results that are too low present a risk of developing or extending an existing blood clot. Results that are too high present an increased risk of bleeding.”

[160] This advice would only have had meaning to the plaintiff if she was informed of her INR and whether it was within, below, or above the target range. She was not given that information.

[161] It is also true that the plaintiff’s INR results were being sent on in paper form by mail to her GP, Dr Powell. Even if he were reading them as they arrived, however, they would, by then, have been several days out of date. In that regard, I accept that the reference in the plaintiff’s consultation with Dr Powell on 23 February 2002 to the plaintiff’s INR having been unstable was not in respect of her then current sub-therapeutic INR levels but related to the history of “spiking” which had occurred in January 2002.

[162] From 16 February 2002, when the plaintiff was being tested every few days and was returning a persistently low INR, the defendant made no attempt to contact the plaintiff either to advise her of the fact that her INR’s were at that level or of the risks which those levels posed for her health. Nor did the defendant take any steps to contact her GP, other than by mailing the lab results, to advise of the situation. This needs to be viewed in the context that Dr Rowbotham herself considered that she was facing a difficult situation in managing the plaintiff’s INR’s and was aware of the risks of under- and over-anticoagulation, and indeed justified her cautious dosage approach on the basis of managing those risks. Dr Rowbotham knew that the plaintiff was at risk of thromboembolism associated with her artificial mitral valve, but assessed the plaintiff as being at greater risk of bleeding if she were over anti-coagulated.

[163] Having regard to the situation of this particular plaintiff, with an artificial mitral valve which of itself dictated caution in respect of the risk of clotting and a recent history of INR instability, and also having regard particularly to the evidence of both Professor Metz and Professor Eikelboom as to the desirability, if not the necessity, to communicate with the patient, I consider that a reasonable Warfarin care haematologist in the position and having the knowledge of the defendant would have contacted the plaintiff:

(a) To advise of the unstable history of INR readings and of the persistent sub-therapeutic levels;

(b) To advise (or at least reaffirm) the risks associated with sub-therapeutic INR readings;

(c) To advise of the approach which was being adopted to incrementally increase dosage levels in an attempt to bring her INR back into range;

(d) To advise the plaintiff that she should consult her G P with respect to management of the risks associated with her sub-therapeutic INR levels.

[164] This contact and advice to the plaintiff should, in my view, have been given once it was apparent that the plaintiff’s INR levels were consistently sub-therapeutic. That certainly would have been, at the latest, at the time of the INR reading of 1.5 on

22 February 2010.

[165] Similarly, in my view, a reasonable Warfarin care haematologist faced with these circumstances would have contacted the plaintiff’s general practitioner upon, at the latest, receipt of the test results on 22 February 2002. The risk of a thromboembolic event occurring in a mitral valve patient required, in my view, that the Warfarin care provider not unilaterally seek to manage the under anti-coagulation with the approach of incrementally increasing dosages but ensure that the plaintiff’s general practitioner, as her primary medical care provider, was alert to the plaintiff’s situation and the risks which were then in play. This required contact with the general practitioner:

(a) To ensure that the general practitioner was aware of the plaintiff’s persistent sub-therapeutic INRs;

(b) To advise of the dosage approach being adopted;

(c) To reaffirm the existence of the risks associated with the sub-therapeutic INR; and

(d) To recommend that the GP undertake or investigate management of the risks associated with the plaintiff’s sub-therapeutic INR levels.

[166] I do not, however, consider that it would have been either appropriate or reasonable for the Warfarin care haematologist to make contact directly with the plaintiff’s cardiologist. Leaving aside any questions as to the protocol of contact between medical specialists, the appropriate chain of contact and advice was from the haematologist to the general practitioner, as the plaintiff’s primary care provider. It was not for the Warfarin care haematologist to instigate contact with the cardiologist. That was a matter for the general practitioner, after receiving the advice from the haematologist, to which I have already referred.

[167] Whilst it was not, for the reasons I have given above, appropriate for the defendant itself to instigate alternative treatment with Clexane or Heparin, it seems to me, in the circumstances of this case, that when advising the GP to undertake or investigate management of the risks then faced by the plaintiff, it would have been reasonably appropriate for the defendant at least to raise the prospect of the GP investigating alternative or supplementary forms of anti-coagulation and also to raise the prospect of this needing to be done in consultation with the plaintiff’s cardiologist.

[168] In reaching this conclusion, I draw not merely on the consistent evidence among the experts as to the desirability of appropriate communication between the Warfarin care haematologist and the patient and the patient’s GP, but also Dr Davidson’s evidence to the effect that not all GP’s are up to date in managing complex anti-coagulation problems and would probably need some guidance. A fortiori in a case such as the present, which Dr Rowbotham described as having presented her with a “difficult management problem” because of the need to balance the risks of a thromboembolic event and an haemorrhagic event, and which involved a patient with an artificial mitral valve who in the weeks immediately preceding the persistent sub-therapeutic levels had demonstrated INR instability. In my view, a reasonable Warfarin care provider would have given the kind of advice and guidance to which I referred in para [167], as part of the guidance expected of and from a specialist Warfarin care service. The giving of this advice and guidance did not involve questions of clinical judgment. By not communicating this advice to the plaintiff and this advice and guidance to her GP, the defendant failed to meet the standard of care required of a reasonable Warfarin care haematologist.

[169] The question then arises as to what is likely to have happened if the defendant had given the advice to the plaintiff and her general practitioner which I consider it should have but did not. Specific questions addressed to Dr Powell concerned his response if he had been told by the defendant that the plaintiff should consult with her cardiologist or that he should administer Clexane to the plaintiff. His response is that he would have followed the advice given by the defendant in that regard. Considering Dr Powell’s evidence as a whole, however, I also consider it more likely than not that if he had, by no later than 22 February 2002 received the advice and recommendations to which I have just referred, he would have referred the plaintiff to her cardiologist, Dr Garrahy. The defendant points to the fact that when the plaintiff was discharged by the defendant into Dr Powell’s care and saw him on 28 February 2002, his only response at that time was to continue with an incremental increase in her Warfarin dose and refer her to QML for ongoing Warfarin care. He did not, at that time, mention the possibility of referring her to her cardiologist. It is not, however, at all clear on the evidence that Dr Powell, when he saw the plaintiff on 28 February 2002, had a full picture of the extent of the plaintiff’s sub-therapeutic readings. He had the current reading of 1.7 from the defendant. Had he been made aware at an earlier stage, however, of the persistent sub-therapeutic levels being returned by the plaintiff and been given the advice which I consider he should have been given, it is, I think, more likely than not that he would have instigated steps with the appropriate specialist with a view to further managing the risks associated with those sub-therapeutic INR levels. The appropriate specialist for such a referral would have been the plaintiff’s cardiologist, and I consider it more likely than not that Dr Powell would have arranged for such a referral. The plaintiff would certainly have accepted and acted on that referral.

[170] It is also clear from Dr Garrahy’s evidence that if the plaintiff had been referred to him at that time (and I accept that he would have been available to attend upon her virtually immediately), then it is more likely than not that Dr Garrahy would have instituted the treatment regime he described in his evidence. The fact that

Dr Hossack disagreed with Dr Garrahy’s proposed treatment regime is really not to the point. The question for present purposes is for me to make an assessment as to what course of events I consider would likely have followed if the defendant and her GP had given the advice which I consider it should have. Similarly, it is neither necessary nor appropriate for me to make a determination as to whether the response proposed by Dr Garrahy would have been that of a reasonable cardiologist in the circumstances. The fact is that if the plaintiff had been referred back to him, that is the treatment he would have put in place.

[171] I find that if Dr Garrahy had instituted the therapeutic procedures he described in his evidence on, or shortly after, 22 February 2002 then it is more likely than not that the risk of the plaintiff suffering a thromboembolic incident would have been ameliorated, and accordingly it is more likely than not that she would not have suffered the stroke she did on 1 March 2002. True it is that Dr Garrahy’s proposed treatment carried with it an increase (perhaps a significant increase) in the risk of the plaintiff suffering an haemorrhagic event. But that was a risk to be managed by him as her treating cardiologist. His management of that risk is not a matter for present adjudication.

[172] In all the circumstances, then, I am satisfied on the balance of probabilities that the defendant’s failure to give advice to the plaintiff and her general practitioner by about 22 February 2002 in respect of the matters outlined above was a breach of the defendant’s duty of care to the plaintiff which was causative of her suffering the stroke on 1 March 2002. Accordingly, the plaintiff has proved her case of liability against the defendant.

Quantum

[227] My assessment of the damages recoverable by the plaintiff is, therefore, summarised as follows:

General damages $150,000.00
Interest on general damages $12,750.00
Past economic loss $284,995.00
Interest on past economic loss $111,575.00
Past lost superannuation $25,650.00
Future economic loss $254,408.00
Wilson v McLeay damages $7,500.00
Interest on Wilson v McLeay damages $1,275.00
Past gratuitous care $270,000.00
Interest on past gratuitous care $45,900.00
Future gratuitous care $651,525.00
Future travel $37,000.00
Future medical expenses $170,000.00
Future equipment $52,675.00
Special damages $117,169.00
Interest on special damages $9,560.00
TOTAL $2,201,982.00

[228] I do not propose applying any further discounting to these damages. In the discounts that I have already applied for contingencies and vicissitudes, I have necessarily taken account of the possibility that the plaintiff may have suffered, or will in the future suffer, some damage as a consequence of her pre-existing heart condition. The defendant did not press for there to be any such further discounting.

David Cormack – Brisbane Barrister

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