confidentiality form only part of the guidance. The authors give ... break the confidentiality of any health care ... duty to inform the worker's employing authority.
LETTERS
Perioperative myocardial infarction in peripheral vascular surgery Various components of care will influence myocardial function EDITOR,-N Mamode and colleagues report the number of cases of myocardial infarction after vascular surgery in their unit but do not seem to have looked critically at the components of care that influence myocardial function in this context.' Most patients with arterial disease will have coronary artery disease and a degree of left ventricular dysfunction due to ischaemia and the frequently associated hypertension. The issue is not whether these problems exist and their consequences but the potential for optimising the cardiovascular system and preventing adverse sequelae. Even after preoperative optimisation there are many factors that can compromise both the delivery of oxygen to the myocardium and the myocardium's demand for oxygen perioperatively, causing worsening left ventricular function without infarct or arrhythmia without infarct. Critical events in this regard include induction of anaesthesia, intubation, surgical stimuli, hypovolaemia, and reversal of neuromuscular blockade. Postoperative hypothermia, pain, hypoxia, hypovolaemia, and anaemia all contribute to subendocardial ischaemia, which manifests as left ventricular dysfunction or arrhythmias; these arrhythmias are in turn aggravated by disturbances of electrolyte concentrations. A considerable number of these components are heavily influenced by the choice of regional versus general anaesthesia and the use of regional anaesthesia as part of a general technique. These components are capable of being minimised, but since their impact is not easily quantifiable they could easily be dismissed as hypothetical. Boyd et al, however, have shown the positive impact of aggressive optimisation of the cardiovascular system and oxygen delivery in high risk surgical patients, with demonstrable improvement in morbidity and mortality.2 Until these components of care are looked at critically, optimised routinely, and audited, Mamode and colleagues' study will remain purely an observation. It is thus difficult to accept the authors' proposal that preoperative stratification in its own right will minimise the risks of vascular surgery.
Their study goes some way to meeting this need. The way in which they present their data, however, makes it difficult to draw useful conclusions. The results of tests of association Q2 and Fisher's exact tests) are shown, but no indication is given of the relative risk associated with each risk factor, and no adjustment is made for the effect of other risk factors. It is not unreasonable to expect that age and perhaps sex (unspecified in Mamode and colleagues' report) may have confounded the associations detected. The type and urgency of surgery should also be taken into account in any analysis. Aortic surgery, which entails cross clamping of the aorta, is a considerably greater cardiovascular insult than peripheral vascular surgery. The risks of emergency surgery have consistently been shown to be greater than those of elective surgery.2 The authors recommend further studies to ascertain the best methods of stratifyfing patients by perioperative risk. Such stratification may be regarded as a form of screening. Effective screening tests are most easily derived from risk factors that have a large effect. Logistic regression analysis and the presentation of adjusted odds ratios would be of considerable value. For a screening test to be of value, treatment should be available for the condition detected by the test. There is probably general agreement about situations in which the risks of surgery are very great. I believe that most authorities would be reluctant to undertake elective aortic surgery on an elderly patient with severe intractable heart failure. A risk index would be of most value in patients for whom the risks of surgery are more difficult to judge-for example, in a middle aged man with controlled angina and moderate left ventricular impairment undergoing revascularisation of the leg. The definitive management of such patients is not clearly established. Some studies have shown benefit from the use of epidural anaesthesia, but this is not a consistent finding across all studies.3 4 If we are to offer our patients more than just an estimate of how likely they are to come to harm then systematic research is needed into the best management of high risk patients undergoing major surgery. SIMON HOWELL Clinical lecturer PIERRE FOEX
Nuffield professor Nuffield Department of Anaesthetics,
John Radcliffe Hospital, Oxford OX3 9DU
Wakefield WF1 4DG
1 Mamode N, Scott RN, McLaughlin SC, McLelland A, Pollock JG. Perioperative myocardial infarction in peripheral vascular surgery. BMJ 1996;312:1396-7. (1 June.) 2 Pedersen T, Eliasen K, Henriksen E. A prospective study of mortality associated with anaesthesia and surgery: risk indicators of mortality in hospital. Acta Anaesthesiol Scand
1 Mamode N, Scott RN, McLaughlin SC, McLelland A, Pollock JG. Perioperative myocardial infarction in peripheral vascular surgery. BMJ 1996;312:1396-7. (1 June.) 2 Boyd 0, Grounds RN, Bennet ED. A randomised clinical trial of the effect of deliberate peri-operative increase of oxygen delivery on mortality in high risk surgical patients. JAMA
4 Bode RH, Lewis KP, Zarich SW, Pierce ET, Roberts M, Kowalchuk GJ, et al. Cardiac outcome after peripheral vascular
M D D BELL Consultant in intensive care
Pinderfields Hospitals NHS Trust,
1993;270:2699-707.
Stratifying patients by perioperative risk is equivalent to screening EDITOR,-N Mamode and colleagues are correct when they state that studies of the risk of perioperative myocardial infarction are needed.'
750
1990;34: 176-82. 3 Tuman KJ, McCarthy RJ, March RJ, Delaria GA, Patel RV, Ivankovich AD. Effects of epidural anesthesia and analgesia on coagulation and outcome after major vascular surgery. Anesth Analg 1991;73:696-704. surgery. Anesthesiology 1996;84:3-13.
Presence of renal artery stenosis may indicate risk
EDITOR,-N Mamode and colleagues' finding of an increased incidence of perioperative myocardial infarction in patients undergoing peripheral vascular surgery is important.' The authors fail
to point out, however, that these patients, in addition to having coronary artery disease, also have generalised vascular disease, which often affects the renal2 3 and carotid arteries. This may have important implications in patients undergoing surgery for peripheral vascular disease. Forty two consecutive patients referred to our institution for investigation of severe ischaemia of the leg underwent renal angiography at the same time as peripheral angiography. Nineteen of the 42 had renal artery stenosis (mean (SD) serum creatinine concentration 112 (40) ,umol/l; mean age 74 (10)). In the 23 patients with no evidence of renal artery stenosis the mean serum creatinine concentration was 97 (23) pmol/l and the mean age 69 (10)). All patients had elective salvage vascular surgery for severe pain or gangrene. Of those with renal artery stenosis, six died postoperatively (three had bilateral, two had severe, and one had moderate renal artery disease; four died of myocardial infarction and two of a combination of heart failure and renal failure). No postoperative deaths occurred among those with no evidence of renal artery stenosis (Fisher's exact test, P = 0.005).2 These findings in patients referred with symptoms of critical ischaemia of the leg suggest that the presence of renal artery stenosis, which can be assessed at the same time as angiography is done, may indicate risk before vascular surgery. We suggest, therefore, that such patients should always be regarded as having generalised vascular disease and need to be assessed not only for coronary artery disease but also for renal artery stenosis and carotid artery disease before surgical revascularisation of the leg. CONSTANTINOS G MISSOURIS Senior registrar in cardiology TIM BUCKENHAM
Consultant radiologist GRAHAM A MACGREGOR Professor of cardiovascular medicine
Blood Pressure Unit, Departments of Medicine and Radiology, St George's Hospital Medical School, London SW17 ORE
1 Mamode N, Scott RN, McLaughlin SC, McLelland A, Pollock JG. Perioperative myocardial infarction in peripheral vascular surgery. BMY 1996;312:1396-7. (1 June.) 2 Missouris CG, Buckenham T, Cappuccio FP, MacGregor GA. Renal artery stenosis: a common and important problem in patients with peripheral vascular disease. Am Y Med 1994;96: 10-4. 3 Salmon P, Brown MA. Renal artery stenosis and peripheral vascular disease: implications for ACE inhibitor therapy. Lancet 1990;336:321.
Authors' reply
EDrTOR,-Our study was aimed primarily at ascertaining the incidence of perioperative myocardial infarction rather than at determining how it might be predicted. We concluded that the incidence is fairly high and that larger studies are needed to define which are the most useful predictors of risk. We agree with M D D Bell that the factors involved in precipitating perioperative myocardial infarction are complex, but we did not claim that stratification would itself reduce the risks of surgery. We aimed to clarify whether the incidence of perioperative myocardial infarction is sufficiently high to justify further attempts at reducing the risk; we showed that it is. Simon Howell and Pierre Foex's plea for a more complex statistical analysis is inappropri-
BMJ VOLUME 313
21 SEPTEMBER 1996
ate, since we believe that this would be a statistically dubious approach in a study with 14 events and 13 variables. We agree, however, that what is most urgently required is effective assessment of risk for the patients at moderate risk, who make up the bulk of our practice; conventional indices of risk have not met this need,' 2 and in a recent study we found the Detsky scoring system to be inadequate at predicting risk (N Mamode et al, XVIIIth congress of the European Society of Cardiology, Birmingham, August 1996). Further to Howell and Foex's comments on other risk factors, we can clarify that female sex was associated with perioperative infarction. Both the type and urgency of surgery were taken into account; the risk was 6% for elective or urgent procedures and 12% for emergency surgery, and the type of procedure was clearly stated in table 1 in our report. Although neither of these factors reached significance, this does not mean that they are not important and underlines the need for larger studies. We are interested in Constantinos G Missouris and colleagues' findings. We are unaware of any studies showing improved perioperative morbidity resulting from preoperative renal or carotid artery screening. Four perioperative cerebrovascular accidents occurred in our study, only one of which occurred after carotid surgery. Coexistent carotid artery stenosis may certainly be an important cause of perioperative morbidity. In our recent work we found that, in 328 patients who had 21 perioperative cardiac events, the two most important clinical predictors of a perioperative myocardial infarction were age and raised preoperative urea concentration (X2 test, P = 0.001; XVIIIth congress of the European Society of Cardiology). Whether poor renal function itself contributes to the risk of perioperative infarction or is simply a marker of severe, generalised atheroma is unclear. Nevertheless, we hope that such findings stimulate more research. N MAMODE
Registrar
PAUL LISTER
J G POLLOCK Consultant vascular surgeon
Consultant in genitourinary medicine and HIV/AIDS Roehampton Clinic, Queen Mary's University Hospital, London SW15 5PN
Ayr Hospital, Ayr KA6 6DX
Peripheral Vascular Unit, Glasgow Royal Infirmary, Glasgow G4 OSF R N SCOTT Consultant surgeon
Monklands Hospital, Airdrie ML6 OJS I Eagle KA, Coley CM, Newell
Time and experience may limit a clinician's inclination to offer adequate discussion before an HIV test, but clinicians can easily ask a health adviser from their department of genitourinary medicine for help (indeed, Scott's hospital is linked to one of the largest HIV testing units in Europe). Health advisers deal daily with HIV testing, including that of urgent inpatient referrals. Their involvement is often pivotal in helping patients cope with their diagnosis and future treatment and in the notification of partners. In my experience, patients very rarely withhold consent for HIV testing if adequate medical explanation is given. So does HIV infection warrant being a special case? Those working in HIV infection would argue that it does and welcome the General Medical Council's guidance HIV Infection and AIDS.2 Although Scott draws parallels with leukaemia and syphilis, there is no other condition that currently combines limited treatment and poor prognosis with length of infectivity and sexual transmission. The implications of HIV infection cannot be overstated, even though medical advances bring some optimism. At present our only truly effective weapon against HIV is the prevention oftransmission. Control of HIV infection requires patients' cooperation, not alienation. Scott advocates that a doctor "should not be required to tell a patient that he or she had an HIV antibody test." This view appals those of us who have to deal with the consequences when patients are given positive results of HIV tests without adequate prior discussion. Although HIV infection needs to be considered proactively in the differential diagnosis of many conditions, including undiagnosed pneumonia, HIV testing cannot at present be considered a routine investigation. Obtaining informed consent should be viewed as an essential and beneficial process and not an unnecessary barrier to testing. Colleagues in genitourinary medicine are more than willing to help.
1 Scott GM. HIV antibody test should be a routine investigation for undiagnosed pneumonia. BMJ7 1996;312:1363.
(25 May.) 2 General Medical Council. Duties of a doctor. London: GMC, 1995.
JB, Brewster DC, Darling RC,
Strauss HW, et al. Combining clinical and thallium data optimizes preoperative assessment of cardiac risk before major vascular surgery. Ann Intern Med 1989;11O:859-66. 2 Prediction of cardiac risk in non-cardiac surgical patients.
Lancet 1987;ii:433-4.
HIV antibody testing should be routine investigation Suggestion is appalling EDITOR,-G M Scott's letter about HIV testing in the investigation of undiagnosed pneumonia raises important issues.1 Scott contends that a clinician's freedom to investigate an illness may be compromised by the requirement for informed consent to HIV testing. This view fails to acknowledge that a clinician's responsibility to investigate and treat can be reconciled with the patient's right to information. HIV testing is important to help confirm or exclude suspected diagnoses. In the case cited, Scott implies that the clinicians were unable to test for HIV because they felt restricted by the General Medical Council's guidelines.2 Scott fails, however, to tell us why they felt restricted. BMJ VOLUME 313
21 SEPTEMBER 1996
"HIV exceptionalism" has been harmful EDITOR,-G M Scott's report of an avoidable death associated with the current restrictions on HIV testing provides yet another argument against HIV exceptionalism.' The policies that have arisen in response to lobbying by AIDS activists have been harmful in other ways. Firstly, there has been the damage to public health measures based on contact tracing. Landis et al reported that only 14% of 534 HIV positive people agreed to notification of their partners and that tracing was successful in only 7% when the best methods were used.2 Secondly, the AIDS lobby pressurised the regulatory authorities to relax the normal requirement for establishing the safety and efficacy of new drugs. The first product, zidovudine, was licensed for use at an unnecessarily high dose. It is known to cause dose dependent toxicity to bone marrow, and many patients have probably died as a result. More recently, 21198 patients received didanosine on "compassionate release," with 63 deaths from acute pancreatitis.' A proper sequence of controlled clinical trials could have minimised the problem. Death in the
cause of political correctness may or may not have been a compassionate release. Surely the time has come to change the policies and treat HIV infection in the same way as other infections, as urged by Bayer4 and Amiel.5 G R VENNING Consultant in pharmaceutical medicine Pharmaceutical Research Services, 14 Lucas Road, High Wycombe, Bucks HP13 6BX
1 Scott GM. HIV antibody test should be a routine investigation for undiagnosed pneumonia. BMJ 1996;312:1363.
(25 May.)
2 Landis SE, Schoenbach VJ, Weber DJ, Mittal M, Krishan B, Lewis K, et al. Results of a randomized trial of parmer notification in cases of HIV infection in North Carolina. N Engl JMed 1992;326:101-6. 3 Schindzielorz A, Pike I, Daniels M, Pachelli L, Smaildone L. Rates and risk factors for adverse events associated with didanosine in the expanded access program. Clin Infect Dis 1994;19: 1076-83. 4 Bayer R. Public health policy and the AIDS epidemic. An end to HIV exceptionalism? N EnglJ Med 1991;324:1500-4. 5 Amiel B. Aids flourishes in a culture of soft soap. Times 1991 Jun 9.
GMC's guidance on HIV infection and AIDS is useful EDrrOR,-Gilles de Wildt and Helen Sweeney express concern' about the General Medical Council's recent guidance on HIV infection and AIDS.2 The points they make about confidentiality form only part of the guidance. The authors give the impression that doctors will break the confidentiality of any health care worker whom they know to be infected with HIV. The guidance should be taken as a whole, and it explicitly states that doctors who are HIV positive should seek specialist advice on the extent to which they should limit their practice. It also states that it is unethical for doctors infected with HIV to put patients at risk by not seeking advice or by failing to act on the advice. With regard to breach of confidentiality, the guidance says that when a doctor is aware that a health care worker who is infected with HIV has not sought or followed advice to modify his or her professional practice, then that doctor has a duty to inform the worker's employing authority. In this situation the health care worker clearly represents a risk of infection to other people and appropriate action to control the risk (modification of practice) has not been taken. It is only in this rare situation that doctors should inform the health care worker's employer. De Wildt and Sweeney state that this situation is not comparable with that of a professional driver who has developed epilepsy, but the issue is exactly the same: the patient represents a clear risk to the health of other people in doing his or her work, and the reason to breach the patient's confidentiality is this risk to others. Obviously, in any circumstances the doctor must first exhaust all other routes to persuade the patient to take advice (in the case of a health care worker) or to give consent (in the case of a professional driver). Only then should the doctor consider breaching
confidentiality. Another issue raised in the article concerns HIV testing and insurance. The Association of British Insurers modified its guidelines in 1994 to require information only on applicants who have had a positive result of an HIV test or treatment for HIV infection.3 Therefore, people should have no concerns about subsequent insurance proposals if the result of an HIV test is
negative. The General Medical Council's new guidelines are useful and clarify a situation that is never easy to handle-namely, when confidentiality can be breached. They also, how751
