Canadian Anaesthetists' Society journal
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The characteristics of the neuromuscular block produced by prolonged succinylcholine infusion were compared in 40 patients anaesthetized with either nitrous oxide with enflurane (1-2 per cent inspired) or nitrous oxide and fentanyl. Neuromuscular transmission was monitored using train-of-four stimulation and the infusion rate was adjusted to keep the first twitch at 10-15 per cent of its control value. Initially, all patients, exhibited a depolarizing-type block all twitches of the train-of-four being roughly the same size, and the infusion rates were similar in the enflurane (54 microgram X kg-1/min) and the fentanyl (58 microgram X kg-1/min) groups. ⋯ Ten minutes after stopping the infusion fourth to first twitch ratios failed to reach 50 per cent in most patients given enflurane who had received more than 6 mg X kg-1 succinylcholine over more than 90 minutes. Corresponding figures for fentanyl patients were 13 mg x kg-1 and 150 minutes. The block in all 15 patients (9 enflurane, 6 fentanyl) who did not recover spontaneously was successfully antagonized with atropine and neostigmine.
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The question posed for this study was: "While holding a watching brief during an uneventful intra-abdominal surgical procedure do anaesthetics adopt the same position in the operating room with reference to the patient's head and "anaesthetic machine" and, if they do, what is it?" A study of the relative positions of the patient, the anaesthetist, and the "anaesthetic machine" during routine laparotomy showed great variation. The implication was that there was also great variation in the amount of movement necessary by the anaesthetist if the same amount of information was to be obtained with the same frequency. The significance of this with reference to the quality of patient care is discussed. The role of changes in apparatus and the declared need for this by anaesthetics is mentioned and recommendations regarding the visual acquisition of data during anaesthesia are made.
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In rat experiments, the relative potency an safety of thiopentone, diazepam and etomidate were assessed using different indices of anaesthesia - loss of righting reflex, prevention of movement and heart rate responses to an noxious stimulus. Log-probit dose-response curves for these end-points and for lethal effect were determined. Etomidate proved to be more potent than thiopentone or diazepam; its relative potency figures varied from 5 to 18 with the use of different end-points of anaesthesia. ⋯ The extreme variability in assessment of relative potency and safety with different end-points of anaesthesia probably indicates that the indices used reflected various components of anaesthesia. It seems likely that for the proper assessment of the potency of intravenous anaesthetics, one index of potency is not sufficient. Several indices of potency corresponding to different components on general anaesthesia must be used.