Effects of One Minimum Alveolar Anesthetic Concentration Sevoflurane on Cerebral Metabolism, Blood Flow, and CO2 Reactivity in Cardiac Patients

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We investigated the cerebral hemodynamic effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane anesthesia in nine male patients scheduled for elective coronary bypass grafting.For measurement of cerebral blood flow (CBF), a modified Kety-Schmidt saturation technique was used with argon as an inert tracer gas. Measurements of CBF were performed before the induction of anesthesia and 30 min after induction under normocapnic, hypocapnic, and hypercapnic conditions. Compared with the awake state under normocapnic conditions, sevoflurane reduced the mean cerebral metabolic rate of oxygen by 47% and the mean cerebral metabolic rate of glucose by 39%. Concomitantly, CBF was reduced by 38%, although mean arterial pressure was kept constant. Significant changes in jugular venous oxygen saturation were absent. Hypocapnia and hypercapnia caused a 51% decrease and a 58% increase in CBF, respectively. These changes in CBF caused by variation of PaCO2 indicate that cerebrovascular CO2 reactivity persists during 1 MAC sevoflurane anesthesia. Implications: We used a modified Kety-Schmidt saturation technique to investigate the effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane on cerebral blood flow, metabolism, and CO2 reactivity in cardiac patients. We found that the global cerebral blood flow and global cerebral metabolic rate of oxygen remained coupled and that cerebrovascular CO2 reactivity is not impaired by the administration of 1 MAC sevoflurane. (Anesth Analg 1999;89:364-9)