Cerebral blood flow and plasma volume during hyperglycemia in the conscious rat

Cerebral blood flow (CBF) and cerebral plasma volume (CPV) were measured under steady-state hyperglycemic conditions in the hemispheres and brainstem-cerebellum of conscious rats. There groups of hyperglycemic animals each having a different level of plasma glucose concentration, 25, 33.3, 44.4 mmol/l, and a normoglycemic control group were studied. CBF was not affected at the hyperglycemic levels of 25 and 33.3 mmol/l. Mean hemispheric and brainstem-cerebellum CBF values appeared lower than in controls at the highest glycemic level although the differences were not statistically significant. CPV was found to be unchanged at the hyperglycemic level of 25 mmol/l, while it was found to be increased in the hemispheres of the animals whose plasma glucose concentration had been elevated to 33.3 and 44.4 mmol/l. The results of the study do not support the claim that hyperglycemia may enhance ischemic brain injury by reducing CBF.