Canadian Anaesthetists' Society journal
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A brief description of the change from a normative evaluation to a formal audit of anaesthesia for neurosurgery is described. The criteria to be applied and their significance for clinical practise are listed. It is emphasized that these items are not presented as criteria for the standard of anaesthesia practised but as matters deserving debate among anaesthetists participating in a formal audit, particularly where the case load does not permit statistical analysis of patient outcome and only discussion of individual patients or small groups is possible. It is suggested, as it has been by others, that formal audit in a department of anaesthesia can be developed as the form of continuing medical education most closely related to the clinical work of the anaesthetists working within it.
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Comparative Study
Prediction of the need for postoperative mechanical ventilation in myasthenia gravis: thymectomy compared to other surgical procedures.
In a recent report Leventhal, Orkin, and Hirsh described a scoring system felt to be of value in predicting the need for postoperative mechanical ventilation in patients with myasthenia gravis undergoing thymectomy. Leventhal, et al. identified four risk factors felt to have predictive value, namely: (1) duration of myasthenia gravis greater than or equal to 6 years, (2) chronic respiratory disease, (3) dose of pyridostigmine greater than or equal to 750 mg per day, and (4) vital capacity less than or equal to 2.9 litres. Forty-six patients with myasthenia gravis who received 68 general anaesthetics were studied retrospectively. ⋯ Using the risk factors of Leventhal, et al., a predictive score was assessed for each patient; the time of postoperative tracheal extubation was also noted for each patient. From this study it was concluded that the scoring system proposed by Leventhal, et al. may have been of some value in predicting whether or not a particular patient undergoing thymectomy was likely to need ventilation postoperatively. In 41 myasthenics who had procedures other than thymectomy, however, this scoring system was found to be of no value.
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A series is presented of 100 patients who underwent direct laryngoscopy under general anaesthesia. Our preferred technique of ventilation is jet insufflation by an injector attached to the blade of the laryngoscope, as it provides the surgeon with a quiet and completely exposed larynx. In nine cases, chest expansion was assessed as inadequate by the anaesthetist. ⋯ Arterial blood gas values indicated that this method resolved the problem of hypoventilation. Although the catheter somewhat limits the view of the endolarynx, the improved ventilation outweighs the drawbacks of this technique. It is suggested that for the obese and/or stiff-necked patient, a nasotracheal catheter be used electively for ventilation.
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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.