Effects of Sevoflurane on Cerebral Blood Flow and Cerebral Metabolic Rate of Oxygen in Human Beings: a Comparison with Isoflurane

Background And Objective: Isoflurane is commonly used for neurosurgery but the effects of sevoflurane on human cerebral blood flow and cerebral metabolic rate of oxygen have not been fully evaluated. We therefore assessed the effects of sevoflurane and isoflurane on global cerebral blood flow and cerebral metabolic rate of oxygen in patients without noxious stimuli or neurological disorders.

Methods: General anaesthesia was induced with midazolam (0.2 mg kg(-1)) and fentanyl (5 microg kg(-1)) in 20 ASA I patients undergoing knee joint endoscopic surgery. Epidural anaesthesia was also performed to avoid noxious stimuli during surgery. Cerebral blood flow and cerebral arteriovenous oxygen content difference was measured using the Kety-Schmidt method with 15% nitrous oxide as a tracer before and after administration of either sevoflurane or isoflurane (1.5 minimum alveolar concentration, 60 min) and cerebral metabolic rate of oxygen was then calculated.

Results: Sevoflurane and isoflurane both increased cerebral blood flow (17%, P < 0.05; 25%, P < 0.05, respectively) and decreased cerebral metabolic rate of oxygen (26%, P < 0.01; 38%, P < 0.01, respectively). There were no significant differences in cerebral blood flow and cerebral metabolic rate of oxygen between sevoflurane and isoflurane.

Conclusions: Sevoflurane and isoflurane similarly increased cerebral blood flow and decreased cerebral metabolic rate of oxygen in human beings anaesthetized with midazolam and fentanyl.