Differences in Cerebral Blood Flow with Pulsatile and Nonpulsatile Flow in Normal and Ischemic Brain

Abstract

The effect of pulsatile versus non pulsatile perfusion on regional cerebral blood flow (CBF) was tested in a canine model with and without focal ischemia. Nine dogs were placed on total cardiopulmonary bypass with a flow rate of 100 cc/kg/min. at normothermia. Control cerebral blood flow measurements were made in both cerebral hemispheres using the hydrogen clearance technique during pulsatile and nonpulsatile perfusion. The cerebral blood flow measurements were repeated after lateralized ischemia was induced by occluding one middle cerebral artery and the ipsilateral carotid artery. Ischemia was confirmed by cerebral blood flow measurements and electroencephalograph changes in these anesthetized animals. In non-ischemic brain, pulsatile perfusion increased cerebral blood flow 19% over that measured during nonpulsatile perfusion. The reduced flow seen with nonpulsatile perfusion never fell into ischemic ranges (i.e., below 25 cc/100 g/min.) in normal brain tissue. However, in brain rendered ischemic by occlusion of conductance vessels, pulsatile perfusion increased cerebral blood flow 55% over nonpulsatile perfusion, presumably by recruiting collaterals more effectively. This study suggests important physiologic benefits from pulsatile perfusion, especially to patients on cardiopulmonary bypass with cerebrovascular insufficiency.