Effects of sevoflurane on cerebral circulation and metabolism in patients with ischemic cerebrovascular disease

Abstract

Background: Sevoflurane is a newly developed volatile anesthetic that has a low blood-gas partition coefficient. The effects of sevoflurane on the cerebral circulation or metabolism in humans have not been studied. The authors examined the cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMR(O2)) during sevoflurane anesthesia. The carbon dioxide response and autoregulation of cerebral circulation were also examined. Methods; Ten patients with ischemic cerebrovascular disease undergoing extraintracranial artery anastomosis were studied. Cerebral blood flow and CMR(O2) were determined by the Kety-Schmidt method using argon. These procedures were performed during the inhalation of 33% N2O, 33% argon, and oxygen with 1.5% sevoflurane (0.88 minimum alveolar concentration). To examine the relationship of CBF to a change in Pa(CO2), CBF was measured repeatedly at steady state Pa(CO2), of 40, 35, and 45 mmHg. Furthermore, CBF was measured before and after an increase in mean arterial pressure (MAP) caused by intravenous infusion of methoxamine to determine the relationship between CBF and MAP. Results: Cerebral blood flow and CMR(O2) were 28 ± 4 ml · 100 g-1 · min-1 and 1.34 ± 0.23 ml · 100 g-1 · min-1, respectively. Cerebral blood flow was found to vary directly with Pa(CO)2 alteration. The slope of the regression line between Pa(CO2) and CBF was 1.29 ml · 100 g-1 · min-1 · mmHg-1. On the other hand, CBF was constant throughout the elevation of MAP with vasopressor. Conclusions: Both carbon dioxide response and cerebral autoregulation were well maintained under 0.88 MAC sevoflurane anesthesia in patients with ischemic cerebrovascular disease.