Effects of methoxyflurane on canine cerebral metabolism and blood flow.

Abstract

The rate of cerebral oxygen consumption (CMRo2) and the cerebral blood flow (CBF) were determined in eight dogs at three end-expired concentrations of methoxyflurane (means >0.1, 0.25, and 0.44 per cent). With each increase in concentration above >0.1 per cent, a significant decrease in CMRo2 was observed (approximately 10 and 25 per cent less than the >0.1 per cent value, respectively). The cerebrovascular effects of methoxyflurane were less striking. At 0.25 per cent, a small but significant increase in CBF and a decrease in (cerebral vascular resistance) CVR were observed, compared with the >0.1 per cent values. No further significant change was observed at higher concentrations. The cerebrovascular responses to changes in Paco2 were tested at 0.25 per cent end-expired methoxyflurane. Over a range of Paco2 of approximately 20 mm Hg (30 to 50 mm Hg), the expected responses of CBF and CVR were observed. The authors conclude that methoxyflurane resembles halothane in its overall cerebral metabolic effects but, unlike halothane, produces only modest changes in CVR and CBF.