Distribution of cerebral blood flow during deep isoflurane vs. pentobarbital anesthesia in rats with middle cerebral artery occlusion

While previous studies have identified a protective effect for barbiturate anesthesia during focal cerebral ischemia, no such effect has been demonstrated for isoflurane. To better understand the effects of these anesthetics on cerebral blood flow and metabolism that might have relevance to their respective potential for cerebral protection, fasted physiologically stable rats underwent autoradiographic determination of CBF and CMRglu during deep isoflurane or pentobarbital anesthesia (burst suppression of EEG). As expected, cerebral blood flow was significantly greater during isoflurane anesthesia (isoflurane = 157 +/- 18 and pentobarbital = 54 +/- 12 ml/100 g/min) while CMRglu values were nearly identical (isoflurane = 35 +/- 5 and pentobarbital = 33 +/- 4 mumol/100 g/min). Additional identically anesthetized rats underwent middle cerebral artery occlusion with CBF autoradiographically determined 1 h later. While the insult resulted in a significant reduction in the ipsilateral hemispheric and cortical blood flow in both anesthetic groups, flow remained at least twofold greater in isoflurane as opposed to pentobarbital-anesthetized rats. When regional flow was assessed, no difference between groups was observed with respect to the area of tissue with flow values falling between 0-10 ml/100 g/min. In contrast, isoflurane-anesthetized rats had significantly less hemispheric and cortical area with flow values in the ranges of 10-20 and 20-30 ml/100 g/min, respectively. These data, therefore, do not support the contention that isoflurane causes maldistribution of CBF during focal ischemia.