The effects of sevoflurane/halothane anesthesia during normo- and hyperventilation on the energy metabolism of the cat brain]

Energy metabolism of the cat brain was studied using phosphorous-31 nuclear magnetic resonance (31P-NMR) during sevoflurane/halothane anesthesia with normo- and hyperventilation. Under normocapnia, the findings associated with abnormal energy metabolism were not observed at concentration of sevoflurane/halothane up to 2 MAC. Meanwhile under hypocapnia by hyperventilation, the value of phosphocreatine began to decrease at and below 20 mmHg of PaCO2 (2 MAC sevoflurane) and 30 mmHg of PaCO2 (2 MAC halothane) respectively. These abnormal findings of brain metabolism were limited to the cases with cerebral blood flow (CBF) of less than a half of control state (nonanesthetized and normoventilated), and they were normalized with increased CBF by the vasoconstrictor, metaraminol. From the above data, it was concluded that the deteriorated energy metabolism by hyperventilation was due to decrease in CBF with hypotension and there was no direct effect on cerebral metabolism with less than 2MAC of both sevoflurane and halothane.