EFFECTS OF PENTOBARBITAL AND ISOFLURANE ON REGIONAL CEREBRAL OXYGEN EXTRACTION AND CONSUMPTION WITH MIDDLE CEREBRAL-ARTERY OCCLUSION IN RATS

Background: When compared with barbiturates, isoflurane may lack prote ctive effects during focal cerebral ischemia. The reason for this diff erence is not clear. in this study, regional cerebral blood flow (rCBF ), arterial and venous O2 saturation, and O2 extraction were compared in the ischemic cortex and in the nonischemic brain regions of rats an esthetized with isoflurane or pentobarbital using a microspectrophotom etric technique that directly measures the O2 saturation of blood in t he small arteries and veins. Methods: Twenty-eight rats were anestheti zed with 1.4% isoflurane or 50 mg/kg pentobarbital. One hour after a m iddle cerebral artery (MCA) occlusion, rCBF was measured in the ischem ic cortex and in the nonischemic brain regions using C-14-iodoantipyri ne in one-half of each group of animals. Regional arterial and venous O2 saturation were determined using microspectrophotometry in the othe r one-half of each group. Results: The rCBF of the ischemic cortex (IC ) and the non-ischemic contralateral cortex (CC) of the isoflurane gro up were significantly higher than those of the pentobarbital group. Th e venous O2 saturation was significantly less, and the O2 extraction w as significantly higher, in the IC than in the nonischemic regions in both groups of animals (pentobarbital group, IC 10.5 +/- 1.1 ml O2 . 1 00 ml blood-1, CC 6.3 +/- 0.7; isoflurane group, IC 10.8 +/- 0.6, CC 5 .9 +/- 0.2). There was no significant difference between the two group s. Conclusions. Because the rCBF was less and the O2 extraction was si milar, O2. consumption in the focal ischemic area of the brain during pentobarbital anesthesia must have been less than that during isoflura ne anesthesia.