Influence of converting enzyme inhibition on isoflurane-induced hypotension for cerebral aneurysm surgery

Twenty-five patients (aged 18 to 72 years), who recovered after the first bleed from a cerebral aneurysm, were operated on under neuroleptanaesthesia. Isoflurane was added to induce hypotension. It was found that the required hypotension (51 (SEM 1) mmHg) could be obtained and maintained at much lower isoflurane concentrations (less than 1%) after blockade of the angiotensin converting enzyme activity by enalaprilat (2.5 mg i.v.) than without such inhibition. During the hypotension which lasted 78 (SEM 10) min, only minor adjustments of the isoflurane concentration (0.70 (0.04%) were needed. The desired level of hypotension was obtained with preservation of the cardiac output and without tachycardia. No resistance to the blood pressure lowering effect of isoflurane was observed. On recovery from anaesthesia, a small increase of blood pressure above control values was seen in 16 patients and was easily reversed by small doses of clonidine (mean total dose: 220 (61) micrograms). The operative conditions were excellent and the postoperative recovery was uneventful and complete in 23 patients.