The renin-angiotensin system and angiotensin converting enzyme (ACE) inhibitors.

Abstract

Anaesthetists will encounter increasing numbers of patients who are receiving long-term treatment with ACE inhibitors for hypertension, congestive heart failure and prophylactically following myocardial infarction. Our understanding of the physiology and pharmacology of the renin-angiotensin system has dramatically increased in the last decade, and has led to the discovery of endogenous renin-angiotensin systems which may be physiologically more important than the better understood circulating system. There are several reports of adverse interactions between anaesthesia and ACE inhibitors, manifested as hypotension and bradycardia, which may be delayed until the postoperative period. The mechanism behind them is not understood and, as yet, no published studies have attempted to address this issue. It is possible, however, that dehydration associated with the pre-operative fast may play an important role. ACE inhibitors may, in the future, prove to be useful in the subspecialties of cardiac and vascular anaesthesia, where they might be used in an attempt to preserve cardiac function following periods of ischaemia and cardiopulmonary bypass, and to avoid renal damage following aortic cross-clamping. Meanwhile, it would seem prudent to exercise caution when anaesthetising patients taking ACE inhibitors and to be fully prepared to treat the hypotension and bradycardia which may occur.