Change of Erectroencephalographic Pattern During Clinical Ether Anesthesia in the Dog

Electroencephalographic patterns observed during increasing depth anesthesia with thiopental sodium-ether, with ketamine hydrochloride-ether and with pentobarbital sodium were correlated with concentration of anesthetic agents in the blood. Analysis of electroencephalogram was made by histogram method.The results are as follows:1) Before anesthesia phase; Beta band of 20-25 Hz waves were shown 60-70% following alpha band was 30%.2) Induction phase; Delta band and theta band were increasing about 40% in place of beta band, but case of ketamine hydrochloride intervenous were increased beta band.3) Maintenance phase; 20-30% ether gas inhalation 5 minutes, a few beta band increased when this stage ether concentration in blood was about 60 mg/dl. Ether concentration in blood was over 70 mg/dl increasing delta band and theta band appearance ratio.4) Ether inhalation 30 minutes stage; Ether concentration in blood of 110 mg/dl when it was delta band only appearance ratio over about 50%.It was suggested that this method of analysis is adaptable to the quantitative study of contribution of each anesthetic agents when used simultaneously, provided that a significant change in EEG patterns and frequency band (delta, theta, alpha and beta waves bands), subject to classification, is produced by the agents considered.From the results of the present work, it was concluded that the changes EEG patterns were closely related to the depth of anesthesia and pharmacokinetics in the dog anesthetized with ether.