ELECTROENCEPHALOGRAPHIC SEIZURE ACTIVITY IN DOGS DURING ANAESTHESIA: Studies with Ethrane, fluroxene, halothane, chloroform, divinyl ether, diethyl ether, methoxyflurane, cyclopropane and Forane

Abstract

Electroencephalographic (e.e.g.) activity was monitored in dogs during anaesthesia with Ethrane, fluroxene, halothane, chloroform, divinyl ether, diethyl ether, methoxyflurane, cyclopropane and Forane to determine whether seizure activity occurred. Four or more dogs were anaesthetized with each agent. Electroencephalographic tracings were obtained at m.a.c. and increasing multiples of m.a.c. unstimulated and in response to hand-clapping. Pacoa was maintained at 20 mm Hg. Seizure-like e.e.g. tracings were seen during anaesthesia with the ethers but not with non-ethers. With fithrane, seizure tracings and focal twitching were seen in response to hand-clapping. With divinyl and diethyl ether, spontaneous seizures occurred at deep anaesthesia (2.5—3 m.a.c). With Forane spontaneous spike activity was seen and with methoxyflurane low amplitude deflections superimposed on a flat background followed hand-clapping. With Ethrane, increasing Pa3 tended to abolish spike and seizure response to hand-clapping. Suxamethonium abolished the muscular twitches but not the e.e.g. seizures with Sthrane