Anaesthesia
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The absorption of nitrous oxide in halothane was studied by bubbling nitrous oxide and nitrous oxide/oxygen gas mixtures through a halothane bottle, using 100% oxygen as a control. The gas volume emerging from the halothane bottle was measured each minute, over a period of up to 15 minutes. ⋯ However, in the presence of nitrous oxide, the initial flow rate of the gas emerging from the halothane bottle was greatly diminished, but then accelerated rapidly to reach that obtained with oxygen. The results suggested that nitrous oxide dissolved in large quantities in halothane, and the data are consistent with an Ostwald coefficient in excess of 4.0.
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A new form of airway has recently been described, which is introduced blindly into the hypopharynx to form a seal around the larynx, so permitting spontaneous or positive pressure ventilation without penetration of the larynx or oesophagus. The further development of this new airway is described and the results of 18 months' clinical experience are presented. ⋯ The incidence of sore throat and other problems was low. Experience of more than 500 cases suggests that the laryngeal mask airway may have a valuable rôle to play in all types of inhalational anaesthesia, while its proven value in some cases of difficult intubation indicates that it may contribute significantly to the safety of general anaesthesia.
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The characteristics of induction with and recovery from isoflurane anaesthesia were studied in 248 children. The mean time to loss of consciousness was 1.5 min (SD 0.5). Tracheal intubation, without interruption of spontaneous ventilation, was accomplished in a mean time of 4.2 min (SD 54 seconds). ⋯ In two further groups of nine children the mean half times of elimination of halothane and isoflurane were 220 seconds and 54 seconds respectively; recovery from isoflurane was markedly faster. Isoflurane is well accepted by children; induction is more rapid than with halothane, and the marked flexibility in the control of its effects are due to its relative insolubility. It has wide application in paediatric anaesthesia.
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Sixty one patients who had suffered intra-operative anaphylactoid reactions were studied. Intradermal testing identified the causative agent in 84% of cases and, in 75% of these, muscle relaxants were responsible. ⋯ The incidence of previous exposure was considerably higher than that reported in the literature. Pancuronium is suggested to be the least likely currently available agent to provoke a major anaphylactoid reaction.