ACE inhibitor premedication attenuates sympathetic responses during surgery

We studied cardiovascular and catecholamine responses for 3 days in three groups of patients undergoing abdominal hysterectomy. The night before surgery and again 2 h before induction of anaesthesia, patients received the ACE inhibitor, ramipril, the beta 1 blocker, metoprolol, or placebo. In the actively treated groups, mean diastolic pressure was reduced during surgery and increases in heart rate and arterial pressure after surgical incision were attenuated. During operation, stroke volume (SV) and cardiac output (CO) were significantly higher in the ramipril group. In contrast, beta 1, adrenergic block caused no significant changes in SV or CO. The concentration of noradrenaline in plasma and urine indicated that ACE inhibition caused attenuated release of noradrenaline. The results support the concept that angiotensin II facilitates release of noradrenaline from sympathetic nerves and that ACE inhibition inhibits this release.