Increase in Extracellular Potassium in the Brain during Circulatory Arrest

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Abstract
The effect of temperature (37.degree., 28.degree. and 18.degree. C), 160 mg/kg lidocaine and 40 mg/kg thiopental on the efflux of cellular K in the cerebral cortex during complete global ischemia was examined. Cerebral ischemia was induced in dogs on cardiopulmonary bypass circulation by stopping the pump. K concentration was measured on the brain surface by a valinomycine-membrane electrode, which in its response corresponded well to an inserted microelectrode. Hypothermia reduced the ischemic K efflux rate to .apprx. 50% at 28.degree. C and .apprx. 25% at 18.degree. C. At all temperature levels lidocaine caused an additional reduction in the K efflux rate of .apprx. 50%, probably by reducing membrane ion permeability in accordance with its local anesthetic action. Thiopental had no effect on the K efflux during ischemia. This study opens the possibility that lidocaine, like hypothermia, may provide protection of the ischemic brain.
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