Cerebral blood flow during anaesthesia: influence of pretreatment with metoprolol or captopril.

We have studied the influence of a beta adrenergic blocking agent and an angiotensin converting enzyme (ACE)-inhibitor on cerebral blood flow (CBF) during general anaesthesia before surgery. Nine patients served as controls and received no special pretreatment. Two other groups were allocated randomly to receive either metoprolol 0.07 mg kg-1 i.v. (nine patients) at the time of induction or captopril 1 mg kg-1 by mouth (11 patients) 1.5 h before induction. There was no significant difference in CBF or CBF values corrected for changes in PaCO2 (CBF corr.) between the metoprolol group and controls. In the group pretreated with captopril, CBF corr. values were significantly lower compared with the metoprolol group. Low CBF corr. in association with low mean arterial pressure was observed in two patients treated with captopril. These findings suggest that treatment with ACE-inhibitors should be discontinued before anaesthesia.