Cardiac and Cerebral Hemodynamics in Drug Induced Postural Collapse

When signs of cerebral ischemia were induced by the administration of hexamethonium or head-up tilting, the cardiac output was reduced in all patients. Although the level of arterial pressure during cerebral ischemia varied between 34 and 100 mm. Hg, cerebral blood flow at this time was reduced to 30.8 ± 4.6 ml./100 Gm. brain/min. Despite a reduction in cardiac output averaging 47 per cent, approximately the same percentage was diverted to the brain during cerebral ischemia.