EFFECTS OF SEVOFLURANE ON CEREBRAL-CIRCULATION AND METABOLISM IN PATIENTS WITH ISCHEMIC CEREBROVASCULAR-DISEASE

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 stud ied. The authors examined the cerebral blood flow (CBF) and cerebral m etabolic rate for oxygen (CMR(O2)) during sevoflurane anesthesia. The carbon dioxide response and autoregulation of cerebral circulation wer e also examined. Methods: Ten patients with ischemic cerebrovascular d isease undergoing extraintracranial artery anastomosis were studied. C erebral blood flow and CMR(O2) were determined by the Kety-Schmidt met hod 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 chan ge 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 a n increase in mean arterial pressure (MAP) caused by intravenous infus ion 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 bl ood flow was found to vary directly with Pa(CO2) 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 e levation of MAP with vasopressor. Conclusions: Both carbon dioxide res ponse and cerebral autoregulation were well maintained under 0.88 MAC sevoflurane anesthesia in patients with ischemic cerebrovascular disea se.