[Anesthetic consequences of hemodynamic effects of angiotensin converting enzyme inhibitors]

Angiotensin converting enzyme inhibitors (ACEI) are used increasingly to treat cardiovascular diseases, and so, therefore, the number of patients scheduled for surgery and treated preoperatively with these drugs. Haemodynamic instability has sometimes been observed during anaesthesia in these patients, leading some authors to discontinue ACEI administration before anaesthesia. However, recent physiological data concerning the renin angiotensin system (RAS) and ACEI pharmacological data may increase our understanding of the mechanisms of cardiovascular interaction between ACEI and anaesthesia. The RAS is involved in blood pressure regulation when extracellular fluid volume is decreased and in case of hypovolaemia, by inducing vasoconstriction and longterm volume regulation. Arterial vasoconstriction is the target for ACEI. However, venoconstriction may maintain venous return and cardiac output in spite of reduced blood volume. On the other hand, ACEI treatment impedes cardiac adaptation to acute changes in extracellular fluid volume. This effect may be increased by underlying pathology (especially in hypertension) as well as by anaesthesia. A combination of an increased sensitivity to acute changes in ventricular load due to treatment with ACEI and anaesthesia in hypertensive patients or in patients with cardiac failure may carry a high risk of hypotension. Specific studies on haemodynamic tolerance of anaesthesia in patients chronically treated with ACEI are required to assess the prevalence of this risk and how to manage it.