Local Cerebral Glucose Utilization during Enflurane and Isoflurane Anesthesia in Rats

Using autoradiographic [^<14>C]-deoxyglucose method, local cerebral glucose utilization (LCGU) was measured in 20 rats anestetized with isomeric volatile anesthetics, enflurane and isoflurane, 0.9 and 1.8 MAC (enflurane 2 and 4%, isoflurane 1.3 and 2.6%). With enflurane, 1.8 MAC, LCGUs in 9 structures were lower than those with 0.9 MAC, while LCGUs in the corpus callosum and the thalamic ventrobasal complex were 70 and 32% higher than those with 0.8 MAC, respectively. With isoflurane, 1.8 MAC, LCGUs in 4 structures were lower than those with 0.9 MAC, and LCGUs in the corpus callosum and the ventrobasal complex remained unchanged. At 0.9 MAC of both anesthetics, LCGUs with enflurane were 38-92% higher than those with isoflurane in 16 of 30 structures studied. At 1.8 MAC, LCGUs with enflurane were higher than those with isoflurane in 12 structures, the difference being most pronounced (156%) in the corpus callosum. In summary, with enflurane anesthesia LCGUs in many brain regions were higher than those with isoflurane and deep enflurane anesthesia increased LCGUs in the corpus callosum and the thalamic ventrobasal complex, suggesting the activation of the commissural and corticothalamic pathways.