Cerebral blood flow and metabolism during hypotension induced with sodium nitroprusside and captopril

Cerebral blood flow and metabolism have been studied in 11 patients during general anaesthesia and hypotension induced with sodium nitroprusside in combination with captopril. Cerebral blood flow was measured, using a Novo Cerebrograph model 10A, after injection of 133 xenon into an arm vein. Arterial and venous blood samples were drawn to calculate cerebral metabolism. Captopril 1 mg.kg-1 orally was given one hour before induction of anaesthesia. The sodium nitroprusside doses ranged between 0.16 and 3.23 micrograms.kg-1.min-1. Mean arterial pressure was reduced 26 per cent to 46 mmHg during hypotension. It is concluded that for the group as a whole there were no changes in CBF and CMRO2 during hypotension. In one patient, however, critical low CBF measurements were recorded during and after hypotension. This indicates the need for further studies concerning the cerebral haemodynamic consequences of captopril and SNP-induced hypotension.