Phenylephrine - induced Hypertension Decreases the Area of Ischemia Following Middle Cerebral Artery Occlusion in the Rat

Oh, Yong Seok

Abstract

The influence of phenylephrine-indueed hypertension on the area of ischemia during brief middle cerebral artery occlusion was studied. Rats were anesthetized with 1. 2 MAC isoflurane and the middle cerebral artery was occluded via a subtemporal craniectomy. Immediately thereafter, in one group (n= 9), arterial pressure was increased 30-35mmHg above the pre-ocelusion level by i. v. infusion of phenylephrine. In a second group (N=10), there was no manipulation of blood pressure. Local cerebral blood flow (1-CBF) was determined autoradiographically 15 min after occlusion. The areas, expressed as a percentage of the total coronal cross sectional area, in which 1-CBF fell within three CBF range: 0-6ml/100 g/min (rapid neuronal death probable); 6-15ml/100 g/min (delayed neuronal death prob- able); and 15-'23 ml/100 g/min (electrophysiologic dysfunction with prolonged survival probable) were measured. The areas in which CBF fell within the two more severely ischemic ranges were smaller in the phenylephrine group than in control animals. For example, in the coronal section in the middle of the MCA distribution, CBF was 0-6 ml/100 g/min in 6.7+/-1.4% of the section in normotensive animals but was in the same CBF range in only 1.7+/-0.6% of the area during phenylephring-induced hyperten sion (p<0.05). For the 6-15ml/100g/min range, the areas were 6.8+/-0.8% (control) and 3.8+/-0.7% (phenylephrine) (p<0.05). For the 15-23 CBF range, there were no differences. The data suggest that phenylephrine-induced hypertension can acutely improve 1-CBF in an area of focal ischemia.