Comparison of the Effects of Isoflurane and Thiopental on Neurologic Outcome and Neuropathology after Temporary Focal Cerebral Ischemia in Primates

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Abstract
In an attempt to determine whether one anesthetic might be clearly advantageous over another in clinical situations of temporary focal ischemia, isoflurane or thiopental (in concentrations producing equal suppression of cerebral function as measured by the electroencephalogram) were studied for their effects on neurologic outcome and cerebral infarct size in pigtailed monkeys exposed to temporary focal ischemia produced by 5 h of middle cerebral artery occlusion (MCAo). Burst suppression was produced for 15 min before MCAo and maintained throughout the ischemic period by 2.18 .+-. 0.11% (mean .+-. SE) end-expired isoflurane or 135 .+-. 18 mg .cntdot. kg-1 thiopental. Mean arterial pressure was supported with phenylephrine and maintained at approximately 90 mmHg in both groups throughout the ischemic period. At the end of the ischemic period, the isoflurane or thiopental was discontinued, allowing the animals to awaken. Intensive care was provided as needed. Neurologic function was scored for 8 days at the end of which surviving animals were killed and the brains were fixed in formalin and then examined for infarct size. There was no significant differences in final neurologic outcome between the animals receiving isoflurane and those receiving thiopental as determined by the Mann-Whitney rank sum test. Neurologic deficit scores ranged from normal (one of eight in group receiving isoflurane and three of nine in the group receiving thiopental) to death resulting from brain injury (three in the isoflurane group and five in the thiopental-treated group). There also was no significant difference in infarct size between the two groups. Infarct size correlated with neurologic outcome (Spearman rank correlation coefficient, rs = 0.74). From this study it is concluded that in situations of temporary focal ischemia when blood pressure is equally maintained, there is no difference in neurologic outcome or in cerebral infarct size when cerebral function is suppressed either by isoflurane or by thiopental anesthesia.