British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Loss of volition and pain response during induction of anaesthesia with propofol or sevoflurane.
We compared the time to reach two anaesthetic end-points during induction of anaesthesia with a potent inhalation agent (sevoflurane) and an i.v. agent (propofol). We used a method to ensure steady breathing during inhalation induction, and measured loss of tone in the outstretched arm and loss of response to a painful stimulus. Thirty-eight female patients (age 39 (9) yr, weight 65 (11) kg, and height 165 (8) cm) (mean (SD)) were randomly allocated to receive either propofol or sevoflurane. ⋯ The variances of these three measurements were not significantly different, indicating that these dose-response relationships were similar. In contrast, only 11 of the patients given propofol lost the response to pain after 2.5xED(50) had been given. These results support previous evidence of substantial differences between anaesthetic end-points, and show that this evidence can be obtained using a simple and rapid method.
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Randomized Controlled Trial Clinical Trial
Effects of desflurane on cerebral autoregulation.
The aim of this study was to determine the effects of desflurane, at 1 and 1.5 MAC, on cerebral autoregulation. Data were analysed from eight patients undergoing non-neurosurgical procedure. The blood flow velocity in the middle cerebral artery was measured by transcranial Doppler ultrasound and cerebral autoregulation was assessed by the transient hyperaemic response test. ⋯ An infusion of phenylephrine was used to maintain pre-induction mean arterial pressure and ventilation was adjusted to maintain the pre-induction value of PE'(CO(2)) throughout the study. Two indices derived from the transient hyperaemic response test (the transient hyperaemic response ratio and the strength of autoregulation) were used to assess cerebral autoregulation. Desflurane resulted in a marked and significant impairment in cerebral autoregulation; at concentrations of 1.5 MAC, autoregulation was almost abolished.
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Randomized Controlled Trial Clinical Trial
Influence of nitrous oxide on induction of anaesthesia with sevoflurane.
Nitrous oxide is often used during inhalation induction of anaesthesia with sevoflurane. Although the value of using nitrous oxide during inhalation induction with other volatile anaesthetics has been studied, the popularity of sevoflurane induction and the different characteristics of this agent make a study of the combination of nitrous oxide with this agent of interest. We compared induction times, oxygenation, and excitatory events during inhalation induction of anaesthesia using sevoflurane, with and without nitrous oxide. ⋯ Mean time to induction of anaesthesia (fall of an outstretched arm) was 102 s in both groups, but excitation (limb or head movement) was more frequent in those receiving nitrous oxide (10 patients) than in those receiving oxygen only (five patients) (P<0.05). Oxygenation was similar in both groups. We conclude that nitrous oxide confers no advantage when anaesthesia is induced with sevoflurane in this way.