Effect of subarachnoid hemorrhage on the extracellular microenvironment

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Abstract
Local experimental subarachnoid hemorrhage (SAH) was produced over the cerebral cortex in 15 cats. The cellular response was monitored using ion-specific electrodes for extracellular K+ and Ca2+ activity, DC cortical potential and electrocorticogram. The response was characterized by a profound cellular depolarization and extracellular Ca2+ depletion which accompanied extracellular K+ accumulation. The prehemorrhage baseline Ca levels measured 1.14 .+-. 0.11 mM, and were lowered to 0.4 to 0.7 mM in different experiments. The K+ accumulation reached levels between 16 and 31 mM from a baseline of 3.17 .+-. 0.52 mM and were cleared to normal or nearly normal within 5 min. The Ca2+ levels returned to normal within 5 min, but remained depressed for the duration of the experiment in 2 animals. Blood extravasated into the subarachnoid space apparently has a direct effect on parenchymal elements. The combination of transient K+ elevations and Ca depression may play an important role in the development of vascular spasm by inducing or facilitating a contraction in the muscular layer in the wall of major intracranial vessels.