Canadian Anaesthetists' Society journal
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The anaesthetic management of cardiopulmonary bypass (CPB) for a patient with biopsy-proven malignant hyperthermia is reported. Specific changes in the technique used, such as venting the oxygenator before use, monitoring mixed venous PO2 and PCO2, as well as the safety of cold hyperkalaemic cardioplegia are described. ⋯ We chose to treat left ventricular dysfunction by aggressive vasodilator (nitroglycerine) therapy. We detected no myocardial or respiratory depression secondary to dantrolene therapy either before or after operation.
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Linear airway dimensions from incisor teeth to vocal cords were measured from radiographs. Normal children were slightly taller and heavier than children being treated for cleft palate and had significantly longer upper airway dimensions. ⋯ Data from normal children in these two studies were used to calculate the distance from lips to mid-trachea to determine optimal length for a tracheal tube. Previously published data on airway lengths in children are reviewed.
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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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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.