The effects of isoflurane on canine cerebral metabolism and blood flow

Abstract

The cerebral metabolic and vascular effects of isoflurane (Forane) were investigated in 6 unmedicated ventilated dogs. At the MAC of this anesthetic (1.4%, end expired) there was a 23% decrease in the rate of cerebral oxygen consumption [cerebral metabolic rate, CMR(O2)] (compared with values at end expired concentrations of <0.1%). At a higher concentration of isoflurane (2.4%, end expired), a 30% reduction in CMR(O2) was observed. Cerebral blood flow (CBF) increased by 33 and 63% at the 1.4 and 2.4% concentrations, respectively. The increase in CBF was due entirely to a decrease in cerebral vascular resistance and occurred despite an accompanying significant decrease in arterial blood pressure. The response of CBF to change in paCO2 was appropriate during isoflurane anesthesia and was not different from that previously observed during halothane and methoxy flurane anesthesia.