Effect of ketamine on local cerebral glucose utilization in fetal sheep.

Ketamine hydrochloride was infused intravenously in eight near-term fetal sheep, in doses ranging from 4.6 to 62.2 mg/kg. Local cerebral glucose utilization was determined by the [14C]deoxyglucose method. Heterogeneity in density of autoradiographs, a prominent feature in untreated fetal brains, was greatly diminished in animals receiving greater than 18 mg/kg, with differences between cerebral cortical gray and white matter virtually disappearing at high doses. In striking contrast to the pale, washed-out appearance in autoradiographs of most cerebral, cerebellar, and brain stem structures was a relatively high density of entorhinal cortex, hippocampus, lateral olfactory tract, and olfactory bulbs. Local cerebral glucose utilization of most gray and white matter structures was elevated in one ketamine-treated fetus experiencing a marked drop in PO2 during the study.