EFFECTS OF HEMORRHAGE ON REGIONAL CEREBRAL BLOOD-FLOW IN AWAKE AND INISOFLURANE-ANESTHETIZED RATS

During hemorrhage, redistribution of cerebral blood flow may occur. We compared the effects of hemorrhage on regional cerebral blood flow in awake rats and in rats anesthetized with 1 % or 2 % isoflurane. In ha lf of each group, regional cerebral blood flow was measured without he morrhage. The other half was slowly bled to a mean arterial blood pres sure of 40-45 mm Hg before measuring the regional cerebral blood flow. Without hemorrhage, the cortical regional blood flow was greater in t he awake animals than that of the caudal part of the brain. In the 2 % isoflurane group, however, the regional cerebral blood flow of the ca udal part was greater than the cortical regional cerebral blood flow. After hemorrhage, a similar decrease (-45 %) of the regional cerebral blood flow was observed in each brain region and the pattern of distri bution of it remained unchanged in all experimental groups. However, t he absolute value of the cortical flow was higher in the awake animals than in the isoflurane groups. Our experiment demonstrated that hemor rhage decreased the regional cerebral blood flow. However, it did not alter the redistribution of the cerebral blood flow in awake animals n or in the animals anesthetized with isoflurane.