The Effects of Nitrous Oxide and Pentobarbital Anesthesia on Local Cerebral Metabolism

Local cerebral glucose utilization (LCGU) in 24 discrete regions of the brain was examined during nitrous oxide and pentobarbital anesthesia. LCGU during nitrous oxide (67%) anesthesia showed remarkable heterogeneity, being highest (97μmol/100g/min) in the inferior colliculus and lowest (25μmol/100g/min) in the corpus callosum. During pentobarbital (30mg/kg) anesthesia, the electroencephalogram (EEC) consisted of 4-6 Hz wave superimposed by 10-15 Hz wave, and LCGU was significantly lower as compared with nitrous oxide group by 20% to 50%. The decrease in LCGU was greater in the regions where LCGU was high during nitrous oxide anesthesia. During combined use of pentobarbital (30lng/kg) and nitrous oxide, LCGU in many brain regions including the reticular formation was higher than during pentobarbital anesthesia alone. Higher dose of pentobarbital (125mg/kg) anesthesia with or without nitrous oxide produced nearly flat EEC, and there was no significant difference in LCGU between the groups with and without nitrous oxide. These results suggest that nitrous oxide and pentobarbital anesthesia affect LCGU in a different fashion, and that nitrous oxide stimulates cerebral glucose metabolism during pentobarbital anesthesia while EEC is still active.