The effect of elevated blood glucose on the electroencephalogram and cerebral metabolism during short-term brain ischemia in fetal sheep

The effect of cerebral ischemia on cerebral metabolism and the electroencephalogram was studied with and without prior glucose infusion in near-term normoxic fetal sheep. At normal blood glucose levels, the electroencephalogram decreased in amplitude during ischemia. At elevated blood glucose levels the electroencephalographic amplitude was much less attenuated by ischemia although Fast Fourier Transforms revealed a shift toward slower frequencies. Under either normal or elevated blood gluocse conditions, ischemia caused cerebral oxygen consumption to decrease, glucose uptake to increase, and a net efflux of lactate to occur. Elevated blood glucose appears to help maintain electroencephalographic activity during ischemia, perhaps by fueling additional anaerobic energy production. The relationship between the electroencephalogram, brain metabolism, and brain damage remains to be defined.