Resuscitation of the monkey brain after one hour's complete ischemia. II. Brain water and electrolytes.

Adult normothermic rhesus monkeys were submitted to one hour's complete cerebral ischemia, followed by periods of blood recirculation varying from 45 min to 24 h. The functional impact of ischemia and the subsequent recovery was monitored by electrophysiological recording and a distinction was made between animals with signs of functional recovery and animals without recovery. Prior to ischemia the water content of the gray matter was 81.1 plus or minus 0.3% (mean plus or minus S.D.) and of the white matter 68.9 plus or minus 0.8%. The sodium-potassium ratio in the gray matter was 0.43 plus or minus 0.02 and in the white matter 0.62 plus or minus 0.06. During one hour's ischemia brain water did not change significantly, but the differences in the sodium-potassium ratio in white and gray matter were reduced. Blood recirculation of the brain after ischemia caused a considerable increase in brain water content and a shift in the sodium-potassium ratio up to 1.0. Calculated brain swelling was maximal after 45 min when it reached 11.1% of the total brain volume in an animal with recovery and 12.2% in another one without recovery. In animals with signs of functional recovery brain swelling rapidly diminished, followed by a more gradual normalization of brain electrolytes within 24 h. In animals without functional recovery electrolyte shifts were irreversible or even progressed further. It is concluded that brain swelling and electrolyte derangements following one hour's cerebral ischemia are fully reversible when signs of functional recovery appear and brain metabolism returns.