Cardiovascular Effects of Sodium Nitroprusside in Cerebral Aneurysm Surgery

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Abstract
Cardiovascular effects of sodium nitroprusside (SNP) were studied in 17 patients undergoing cerebral aneurysm surgery under controlled hypotension. In 10 patients O2 uptake was also calculated. Mean arterial blood pressure was decreased from 91 to 58 mmHg by SNP due to reductions in both total peripheral resistance (29%) and cardiac output (15%). Mean right atrial and pulmonary capillary wedge pressures were reduced during hypotension. Total O2 uptake remained constant throughout the procedure. There was no significant change in arterial O2 tension in the hypotensive period, but after discontinuation of SNP infusion it was significantly increased. The hemodynamic effects of SNP in patients with a recent subarachnoid hemorrhage and its effect on blood oxygenation are discussed. The fall in cardiac output is related to a reduction of central blood volume and might be more pronounced in these patients than in normal subjects.