141 relation between coffee consumption and infarction or associated death. Similarly, the retrospective study by Hennekens et a!,l8 shows that the increased risk, if any, of M.i.-associated’ death to coffee drinkers is very slight. However, retrospective studies29 30 show a much greater correlation between coffee consumption and M.l. Hennekens et al. 28 examined patients who died from their coronary heart disease, while both Jick et a1.29 and Vessey3o selected patients who survived the infarct. Therefore those workers who found a correlation between coffee drinking and risk of M.!. consistently chose patients who lived through the infarct, while those who reported no correlation either did not select on the basis of survival or chose only those who died from M.L This difference in selection suggests that perhaps two different effects are being reflected in these studies-namely, the effect of coffee consumption (1) on M.L incidence and (2) on death due to the infarct. Our findings suggest that long-term coffee consumption might be inversely correlated with sudden death due to infarc-

tion, regardless of caffeine’s effect

frequency of infarclong-term oral caffeine administration (at a dose approximately equal to 6-8 cups of coffee/day in man) show a reduced susceptibility to arrhythmogenesis. The ventricular tachycardia threshold (v.T.T.), as measured by the smallest current necessary to generate sustained tachycardia, is more than twice as great in those rats receiving caffeine (90 mg/kg/day for 11 weeks) as in watertreated controls. Conversely, those animals receiving only a single oral caffeine injection show a 25% decrease in v.T.T. This reduction in threshold with a single caffeine dose is consistent with the findings of Bellet et a1.31 who demonstrated that an intravenous caffeine injection reduced threshold by 30 in dogs. The clinical importance of the single caffeine administration remains questionable, however, in that coffee is usually consumed daily over long periods of time. tion. We found that

rats

on

the

treated with

We believe that the v.T.T., like the ventricular fibrillation

threshold,32 can provide an estimate of susceptibility to lifethreatening arrhythmias. Since the mechanism of sudden cardiac death associated with M.i. is often due to ventricular fibrillation,33 our results support the possibility that chronic coffee drinkers who have an M.I. tend to succumb to sudden death less often than do non-coffee drinkers who also develop infarction. Although these results do not reflect upon the relationship of caffeine intake and the incidence of infarction, they suggest that lethality due to infarcts may be diminished by chronic caffeine. This distinction between caffeine effects on incidence and lethality of infarcts may explain the difference in findings between clinical studies with different methods of patient selection. Department of Pharmacology and Toxicology, University of Rhode Island, Kingston, Rhode Island 02881, U.S.A.

FRED A. ROTENBERG JOHN J. DEFEO ALVIN K. SWONGER

ANÆSTHETICS AND ABORTIONS

SiR,—The overreaction to reports of possible effects of inhalation of anxsthetic agents on the reproductive performance of operating theatre staff seems to me to be of greater concern than the unproven complications which invoked the original response. Inconsistencies in the data cast considerable doubt

the validity of the conclusions. The series of Cohen et al.,l while superficially convincing, contains so few cases that the conclusion that "there can be little doubt that the spontaneous miscarriage rate is significantly higher in both operating room nurses and anesthetists" must be viewed with the utmost scepticism. The incidence of spontaneous abortions in retrospectively analysed pregnancies gives estimated losses of between 5.6% and 26-8%. The American Society of Anesthesiologists Ad Hoc Committee3 found tfiat the figures for both exposed and non-exposed individuals, excluding paediatricians, are comparable with those in many other series and that the differences between the exposed and non-exposed groups are small compared with that between non-exposed paediatricians and non-exposed nurses. It seems very unwise to compare the abortion-rates of exposed staff with those of non-exposed paediatricians and non-exposed nurses without first accounting for the differences in the latter two groups. However, the A.S.A. has done so in concluding that the risk to exposed personnel is as high as twice that in non-exposed staff. If the paediatricians are excluded then the differences between exposed and non-exposed individuals may be of marginal statistical significance, but their biological significance is highly on

questionable. The British survey4 has a remarkably low spontaneous abortion rate in non-exposed individuals in a very small number of actual abortions. Furthermore, juggling with the controls can vary the abortion-rate in the non-exposed group from 5-5% to 9.2%, a change comparable with that between non-exposed (10-9%) and exposed mothers (18-0%). The information gathered in the published series is, in my opinion, inadequate and certainly does not warrant the sweeping conclusions which are said to follow from the analysis of the data. Spontaneous abortions cannot, and should not, be considered to be a homogeneous group. There are many (often unknown) aetiological factors, and abortions occurring at different gestations show differing and characteristic pathological changes which indicate they may be of different mtiologies.1 No information is available as to the nature of the aborted conceptuses and it is therefore impossible to determine whether the pattern of abortion in exposed individuals differs in any way from that in a control population. If a specific agent is to be incriminated then it might be anticipated there will be a surplus of conceptuses in a particular pathological group. The data do not even indicate how many of the aborted pregnancies were confirmed by a positive pregnancy test and/or examination of the products of conception. The role of anaesthetics in the genesis of congenital malformations is in my opinion equally inconclusive, since the numbers of cases are very small and many of the excess malformations in the exposed group 6 are very minor. I would not deny that there are grounds for a well-constructed prospective study which should include proper examination and classification of the aborted products of conception. I would, however, suggest that the arguments require further evaluation before large sums of the already very scarce funds of the Health Service are spent on scavenging these gases as you clearly suggested in a recent editorial.’ I support the view that it is time to stand back and reassess the situation, since the circumstantial evidence is by no means as strong as has been

suggested.8

Birmingham Maternity Hospital, Queen Elizabeth Medical Centre, Birmingham B15 2TG 1.

Cohen,

E. N.,

D. I. RUSHTON

Bellville, J. W., Brown, B. W. Anesthesiology, 1971, 35, 343.

343. 28.

29 30 31 32. 33

Hennekens, C. H., Drolette, M. E., Jesse, M. J., Davies, J. E., Hutchison, G. B. New Engl. J. Med. 1976, 294, 633. Jick H., Miettinen, O. S., Neff, R. K., Shapiro, S., Hemonen, O. P., Sloan, D ibid. 1973, 289, 63 Vessey, M. P. Lancet, 1972, ii, 1278. Bellet, S., Horstmann, E , Roman, L. R., DeGuzman, N. T., Kostis, J. B. Am. Heart J. 1972, 84, 215. Moore, E. N., Spear, J. F. Arch intern. Med. 1975, 135, 446. Lown, B., Klein, M. D., Hershberg, P. I. Am. J. Med. 1969, 46, 705.

2. Pettersson, F. Epidemiology of early pregnancy wastage, 1968, p23. 3. Cohen, E. N., Brown, B. W., Cascorbi, H. F., Corbett, T. H., Jones, T. W., Whitcher, C. E. Anesthesiology, 1974, 41, 321. 4. Knill Jones, R. P., Newman, B., Spence, A. A. Lancer, 1975, ii, 807. 5. Rushton, D. I. Unpublished. 6. Corbett, T. H., Cornell, R. G., Endres, J. L., Lieding, K. Anesthesiology, 1974, 41, 341. 7. See Lancet, 1976, i, 842. 8. Br. J.Anœsth. 1976, 48, 397.

Letter: Anaesthetics and abortions.

141 relation between coffee consumption and infarction or associated death. Similarly, the retrospective study by Hennekens et a!,l8 shows that the in...
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