British journal of anaesthesia
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Clinical Trial
Can prolonged expiration manoeuvres improve the prediction of arterial PCO2 from end-tidal PCO2?
We have studied, in 16 patients undergoing thoracoabdominal oesophagectomy, if two prolonged expiration manoeuvres improve prediction of arterial PCO2 (PaCO2) from end-tidal PCO2 (PE' CO2). PE' CO2, PCO2 at the end of a simple prolonged expiration (PE1 CO2), and PCO2 at the end of a prolonged expiration preceded by sustained hyperinflation of the lungs (PE2 CO2), were measured during laparotomy, in the lateral thoracotomy position during two-lung ventilation, and after transition to one-lung ventilation. (PaCO2-PE' CO2) was 1.3 (SD 0.4) kPa during laparotomy and this remained stable throughout the study. ⋯ However, PE1 CO2 and PE2 CO2 did not agree more closely with PaCO2 than PE' CO2 at any stage of the study. We conclude that these manoeuvres did not improve estimation of PaCO2 from PE' CO2.
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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.