[The effects of hyperglycemia on ischemic brain edema]

The effects of hyperglycemia on ischemic brain edema in rats were studied by measuring the local changes in water content of brain and cerebrovascular permeability using a transient middle cerebral artery (MCA) occlusion model. Rats, fasted except for water for 12-16 hours, were used. They were anesthetized with halothane and the stem of the left MCA was occluded for 2 hours by a microclip. Reperfusion was performed by removal of the clip. The rats were allowed to awake from anesthesia after removal of the clip. Hyperglycemia was induced by intraperitoneal injection of 50% glucose and same volume of physiological saline was injected intraperitoneally 20 minutes before MCA occlusion in control rats. Cerebrovascular permeability was measured by quantitative autoradiography using 14C-alpha-amino-isobutyric acid (14C-AIB) 2 hours after reperfusion. The specific gravity of cerebral tissue, determined by the gradient column with bromobenzene and kerosene, was used to study local changes in brain water content 2 hours after MCA occlusion and 2 hours after reperfusion. In hyperglycemic rats, plasma glucose content-ration rose to over 500 mg/dl at the peak and then declined. A hyperglycemic state around 300 mg/dl was maintained during the experiments. Elevation of hematocrit and plasma osmolarity were observed in hyperglycemic rats. At 2 hours after MCA occlusion, specific gravity of the brain was decreased in the left MCA territory, especially in the frontal cortex, in both groups. The decrease in the frontal cortex in hyperglycemic rats was statistically significant compared with that in the control rats.(ABSTRACT TRUNCATED AT 250 WORDS)