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

Cerebral blood flow (CBF) and metabolism have been studied during general anaesthesia with enflurane and hypotension induced with sodium nitroprusside (SNP) in combination with metoprolol in nine ASA Grade I patients undergoing surgery for deviation of the nasal septum. Mean arterial pressure (MAP) was reduced by 31% to a mean of 47 mmHg using metoprolol 0.15 mg kg-1 and SNP 0.46 mg kg-1. There was no reduction in CBF during the hypotensive period. Cerebral metabolic rate of oxygen (CMRO2) was also unchanged during hypotension. We conclude that in healthy individuals anaesthetized with enflurane, SNP in combination with metoprolol reduces MAP to the desired level without changing CBF or CMRO2.