Ionic shift in cerebral ischemia.

Electrolyte and water contents were measured in gerbil brain after unilateral cerebral ischemia. Increase of Na+ and water, and decrease of K+ occurred after an ischemic period of 30 minutes. However, these abnormalities disappeared within 3 hours. When the ischemic period was extended to 3 hours, the abnormalities observed after ischemia for 30 minutes were again encountered, but more significant alterations occurred immediately after re-establishment of blood flow. In addition to more pronounced increase of Na+ and decrease of K+, Ca2+ became significantly elevated after recirculation for 15 minutes and progressively increased during recirculation for 3 hours. The steady rise of Ca2+ appears to be related to the irreversibility of cerebral ischemia.