The electroencephalographic changes of propanidid anaesthesia have been the subject of a previous publication' and EEG tracings have been included in a second paper2. The purpose of this study was to repeat that work under conditions of greater uniformity, in order to permit the description of distinct electroencephalographic levels. Such levels can form an objective basis for assessment of the depth of anaesthesia. The electrocardiogram was recorded simultaneously, and in 25 of the patients the exhaled carbon dioxide tension was also recorded continuously.
METHODThe investigations were done on 40 adult volunteers, of whom 28 were male. All were patients about to undergo elective surgery and their ages ranged from 17 to 83. The nature of the investigation was explained to the subjects prior to premedication and their consent obtained. All the subjects appeared free of disease of the cardiovascular, respiratory or nervous systems. They were divided into four groups of 10 each. Two groups, (in table 1) received 7mg/kg propanidid and two groups received 10mg/kg propanidid. One group at each propanidid dose level received atropine 0.4 to 0.6mg intramuscularly for premedication. The other two groups were premedicated with papaveretum 10 to 20mg and hyoscine 0.3 to 0.4mg intramuscularly.Electrocardiograph plates were attached to the limbs and 27sw gauge needles were inserted subcutaneously at the vertex and temple of the dominant hemisphere to record the EEG. Lead 2 of the ECG and the EEG were recorded on a Grass 5D polygraph. The exhaled carbon dioxide concentration was recorded by a Beckman L.B.1 infra-red analyser, sampling from under the face mask at the rate of 200ml/min.The subjects were pre-oxygenated for three minutes, using a non-rebreathing valve and a well fitting face mask. An in-dwelling needle was placed in a vein of the forearm or hand and recording was then begun. The calculated dose of propanidid was injected, as a 5 % solution, over 30
