male-to-female to female-to-male transmission. As we stat¬ ed,2·5 prevention efforts should not be compromised by the false belief that men are not at risk.

Nancy S. Padian, PhD Stephen C. Shiboski, PhD University of California, San Francisco Nicholas P. Jewell, PhD University of California, Berkeley 1. De Vincenzi I, Ancelle-Park R. European Study Group of Heterosexual Transmission of HIV: comparison of female-to-male and male-to-female transmission of HIV in 563 stable couples. BMJ. 1992;304:809-813. 2. Padian NS, Shiboski SC, Jewell NP. Female-to-male transmission of human immunodeficiency virus. JAMA. 1991;266:1664-1667. 3. De Vincenzi I. Heterosexual transmission of HIV. JAMA. 1992;267:1919. 4. Padian NS, Shiboski SC, Jewell NP. The effect of numbers of exposures on the risk of heterosexual HIV transmission. Infect Dis. 1990;161:883-887. 5. Padian MS, Shiboski SC, Jewell NP. Heterosexual transmission of HIV. JAMA.

1992;267:1918-1919.

Weighing the Risk Factors in Coronary Artery Bypass Surgery To the Editor.\p=m-\Bycombining men and women in their analysis of 5051 consecutive patients (of whom 1040 [20.6%] were women) Higgins et al1 may have weakened the power of their excellent clinical severity score for coronary artery bypass patients. Even taking into account the possibility of a misprint in the abstract, where a "body weight of 65 kg or more" was stated to be "predictive of morbidity," the issue of body weight requires some clarification. All three tables in the article identify weight that is 65 kg or less as a "preoperative factor" increasing the odds ratios, and the "Comment" section clearly refers to low body weight as an independent risk factor. Though the present study did not identify female gender as a risk factor (in contrast to other reports), the authors subscribe to the idea that smaller body size might explain increased risk in women. It is true that there is a relationship between stature (height) and weight; however, the former is a better measure of body size, being more strongly correlated with lean body mass. Using 65 kg as a cutoff point has different implications in men and women. In men it represents underweight, moving them to the left on the J-shaped mortality curve ofthe general

population,2 which might contribute to the observed increased mortality in coronary artery bypass graft surgery patients, with or without controlling for smoking.3 In women, however, 65 kg is overweight, moving them to the right of the nadir of J-shaped curve, and is also associated with increased mortality in the general population.4 In studies in which data from men and women can be analyzed together—and the study of Higgins et al might not be such a study—it is better to use body mass index (Body Mass Index=[Weight (kg)]/[Height (m)]2), which also allows comparisons between populations. the

John G. Kral, MD, PhD State University of New York Health Science Center at Brooklyn 1. Higgins TL, Estafanous FG, Loop FD, Beck GJ, Blum JM, Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary

artery bypass patients:

a

clinical

severity score. JAMA. 1992;267:2344-2348.

2. Bray GA. Complications of obesity. Ann Intern Med. 1985;103:1052-1062. 3. Vandenbroucke JP, Mauritz BJ, de Bruin A, Verheesen JHH, van der Heide\x=req-\ Wessel C, van der Heide RM. Weight, smoking, and mortality. JAMA. 1984;252:

2859-2860. 4. Manson JE, Colditz GA, Stampfer MJ, et al. A prospective study of obesity and risk of coronary heart disease in women. N Engl J Med. 1990;322:882-889.

In Reply.\p=m-\Wethank Dr Kral for the opportunity to correct a misprint in the abstract of our recent article.1 Increased risk was noted with body weight of 65 kg or less, as is correctly stated in the text and tables. The median weight of men in this study was 81 kg; that of females was 67 kg. Increased weight

in either group was associated with decreased mortality, although one could argue for use of a different cutoff point by gender. We also agree with Kral that body mass index is preferable to body weight as a measure of size, but our initial data set did not include height. A multicenter validation of this score is planned, and any update of this model will include body mass index rather than body weight. Risk factors examined separately for men and women were similar except that body weight disappears in multivariate analyses within gender groups. Also, when body weight is forced out of the combined population logistic model, then female gender reappears as a risk factor. We conclude from this information that the increased mortality risk in women, as noted by other investigators,2'4 is due primarily to smaller body size in women. Referral bias that causes women to present at a later disease stage may also be a factor.5 Al¬ though for purposes of scoring, gender and weight are rough¬ ly interchangeable, we felt that body weight was the pre¬ ferred item to score, since the increased risk ascribed to female gender is not seen when body size is considered.6 Thomas L. Higgins, MD Fawzy G. Estafanous, MD Floyd D. Loop, MD Gerald J. Beck, PhD James M. Blum, MS Lata Paranandi, MSHP Cleveland (Ohio) Clinic Foundation 1. Higgins TL, Estafanous FG, Loop FD, Beck GJ, Blum JM, Paranandi L. Stratification of morbidity and mortality outcome by preoperative risk factors in coronary artery bypass patients: a clinical severity score. JAMA. 1992;267:2344-2348. 2. Kennedy JW, Kaiser GC, Fisher LD, et al. Multivariate discriminant analysis of the clinical and angiographic predictors of operative mortality from the Collaborative Study in Coronary Artery Surgery (CASS). J Thorac Cardiovasc Surg. 1980;

80:876-887. 3. Parsonnet V, Dean D, Bernstein AD. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation.

1989;79(suppl I):I-3-I-12.

4. Hannan EL, Kilburn H Jr, O'Donnell JF, Lukacik G, Shields EP. Adult open-heart surgery in New York State: an analysis of risk factors and hospital mortality rates.

JAMA. 1990;264:2768-2774. 5. Khan SS, Nessim S, Gray R, et al. Increased mortality of women in coronary artery bypass surgery: evidence for referral bias. Ann Intern Med. 1990;112:561-567. 6. Loop FD, Golding LAR, MacMillan JP et al. Coronary artery surgery in women compared with men: analyses of risks and long-term results. J Am Coll Cardiol.

1983;1:383-390.

Relief From Pain and the Double Effect To the Editor.\p=m-\Wilsonet al1 recently reported their findings regarding the "Ordering and Administration of Sedatives and Analgesics During the Withholding and Withdrawal of Life Support From Critically Ill Patients." Two observations can be made regarding this research. First, it does not seem to be fair to compare comatose patients as a control group with noncomatose patients when examining the amount of time until death once life support was withheld or withdrawn. As the authors indicate, the comatose patients would have been expected to die more quickly. However, to design a study comparing two groups of noncomatose patients in which one group is given sedatives and analgesics when life support is withheld or withdrawn and the other group is provided with no sedative or analgesic relief would be unethical, for it would violate the basic principle of beneficence. An argument could be made that with informed consent from the latter group such a research protocol could be initiated. However, a critically or terminally ill patient who meets the inclusion criteria is so psychologically traumatized that it is highly doubtful whether informed consent could even be obtained. A second observation concerns the authors' understanding of the principle of double effect. Although the authors initially summarize the principle correctly, they seem to conclude that since hastening death was never given as the only reason for

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Weighing the risk factors in coronary artery bypass surgery.

male-to-female to female-to-male transmission. As we stat¬ ed,2·5 prevention efforts should not be compromised by the false belief that men are not at...
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