British journal of anaesthesia
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We have assessed a range of high volume, low pressure (HVLP) cuffed tracheal tubes in a benchtop model, for leakage of fluid from above the cuff to the model trachea below, during various ventilatory modes. Rapid leakage occurred in the model during all modes of ventilation, unless tracheal pressure was greater than the height of fluid in the column above the cuff. This leakage occurred preferentially down longitudinal folds that occur in the HVLP cuff wall. This model suggests that, if a longitudinal fold within the cuff wall is patent, then the possibility exists of subglottic to tracheal leakage.
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Case Reports
Conservative management of extradural abscess complicating spinal-extradural anaesthesia for caesarean section.
We report a case of lumbar extradural abscess that presented 9 days after an elective Caesarean section performed under combined spinal-extradural anaesthesia. This was successfully treated conservatively with full recovery. The clinical course included development, and then resolution, of mild paraparesis. Conservative treatment of an extradural abscess in the obstetric population has not been described previously.
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The auditory middle latency response (AMLR) and the 40-Hz auditory steady-state response (40-Hz ASSR) are evoked potentials which possibly arise from the same generators in the primary auditory cortex. Both responses are attenuated by most general anaesthetics. Ketamine, however, has been reported to have no effect on the AMLR. ⋯ The 40-Hz ASSR and EEG revealed no consistent differences between conscious and unconscious patients. No relationship could be demonstrated between the increase in amplitude of the 40-Hz ASSR or of relative theta power (the hallmark of ketamine effect) and loss of responsiveness to commands. We conclude that ketamine, unlike other anaesthetics, increases the amplitude of the 40-Hz ASSR.
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The antinociceptive effects of intrathecal 5-HT, fentanyl, ICI197067 and U50488H were assessed by electrical current nociceptive threshold and tail flick latency measurements. Equieffective doses of these agonists were then given intrathecally with a range of doses of naloxone or the highly selective mu opioid antagonist, beta-funaltrexamine. Antagonist dose-response curves were plotted. ⋯ Cross tolerance in both directions was demonstrated between intrathecal fentanyl and 5-HT in the electrical test but not in the tail flick test. We conclude that intrathecal 5-HT caused spinally mediated antinociceptive effects revealed by electrical current and tail flick latency tests. The antinociceptive effects in the electrical test involved spinal cord mu opioid receptors.
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We have compared the responses of four groups of anaesthetists, with different durations of clinical experience, to nine different simulated emergencies. Five anaesthetists in each group completed each of the nine simulated emergencies. ⋯ However, all groups made serious errors in both diagnosis and treatment, and accepted treatment guidelines were not followed. We have shown that a simple, inexpensive simulator can be used to evaluate the performance of anaesthetists of different durations of clinical experience.