Ischemic brain edema: comparative effects of barbiturates and hypothermia

The effect of pentobarbital and hypothermia on the development of ischemic brain edema was studied in 23 rhesus monkeys undergoing transorbital middle cerebral artery occlusion. Fifteen additional animals served as unclipped controls. Regional cortical cerebral blood flow (rCBF), arteriovenous oxygen content difference (AVDO2), and regional cortical metabolic rate of O2 (rCMRO2) were measured hourly until sacrifie 11 hours postocclusion, at which time ischemic cerebral edema was measured. In 8 animals no treatment followed the occlusion, and these developed edema. In 7 animals pentobarbial 14 mg/kg was administered intravenously 30 min after occlusion and 7 mg/kg every 2 hours thereafter. In this group ischemic brain edema was negligible. In 8 animals, hypothermia to 25.9 +/- 0.5 degrees C was started 30 min after occlusion and maintained until sacrifice; ischemic brain edema was not significantly altered from untreated-clipped animals. On the basis that both pentobarbital and hypothermia produced similar changes in rCBF, AVDO2, and rCMRO2, but only pentobarbital prevented edema, it is postulated that the mode of action of barbiturates in preventing ischemic brain edema is not entirely related to their known effect on blood flow and metabolism.