Cardiovascular effects of nitroglycerin as a hypotensive agent in cerebral aneurysm surgery.

The cardiovascular effects of nitroglycerin (TNG) were studied in 20 patients undergoing cerebral aneurysm clipping under controlled hypotension. Total oxygen consumption was also calculated in 15 patients. Mean arterial blood pressure was reduced by 36% from 91 to 58 mmHg (12.1 to 7.7 kPa) by TNG due to decrease in both total peripheral resistance (16%) and cardiac output (24%). Right atrial and pulmonary capillary wedge pressures were reduced during hypotension, indicating a decrease in venous return to the heart. There were no significant changes in total oxygen consumption. It is concluded that the fall in cardiac output results from a reduction in central blood volume due to venous pooling of blood, and that TNG has no major overall metabolic effects.