British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Bispectral analysis of the electroencephalogram does not predict responsiveness to verbal command in patients emerging from xenon anaesthesia.
The bispectral index (BIS) is derived empirically from the electroencephalogram database of patients receiving common anaesthetics, but it may not be valid for uncommon agents. Therefore, we investigated how xenon affects the BIS. Nine and 11 patients were anaesthetized with 0.8 of the minimal alveolar concentration (MAC) of isoflurane (0.92%) and xenon (56%), respectively. ⋯ In contrast, four patients receiving xenon responded to verbal command while the BIS was below 50 [median 45 (range 41-49)]. The remaining seven patients in the xenon group awoke when their BIS was greater than 80 [median 96 (range 82-98)], but in four of them the BIS was no greater than 50 when the xenon concentration was only 0.1 MAC (7%) higher than that associated with awakening. We conclude that low BIS values (< 50) do not guarantee adequate hypnosis during xenon anaesthesia.
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Randomized Controlled Trial Comparative Study Clinical Trial
Transcranial magnetic-evoked potentials under total intravenous anaesthesia and nitrous oxide.
Magnetic stimulation of the cortex and recording of the motor-evoked potentials (MEPs) by electromyography (EMG) is a well proven method to assess the descending pathways of the spinal cord and detect neurological impairment. We have assessed, in 33 adult patients undergoing spinal surgery, the influence of four total i.v. anaesthesia regimens (TIVA) on this recording technique. In 20 patients, the effect of 50% nitrous oxide was also studied. ⋯ Propofol (in combination with alfentanil or ketamine) showed marked depression of the MEP amplitude and the lowest success rates of stimulation. The latencies did not change at all. The addition of nitrous oxide significantly depressed the registered MEPs and lowered the success rates.
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Randomized Controlled Trial Comparative Study Clinical Trial
Nodal rhythm and bradycardia during inhalation induction with sevoflurane in infants: a comparison of incremental and high-concentration techniques.
We studied heart rate and rhythm changes during sevoflurane inhalation induction in 60 healthy, unpremedicated infants. Patients were allocated randomly to receive an incremental (2% sevoflurane, increased every four to six breaths by 2% increments, to 8%) or high-concentration induction technique (8% sevoflurane from the outset). The ECG was recorded for 330 s (30 s pre- and 300 s postinduction) using a mini-Holter device (Recollect Dual Channel, Hertford Medical) and later analysed by an independent observer. ⋯ The onset of nodal rhythm was associated with bradycardia (< 80 bpm) in seven out of 12 cases, and occurred significantly earlier in the high-concentration group (median 123 (range 99-139) s versus 164 (127-138) s). Its duration was similar in both groups (62 (2-84) s versus 90 (20-167) s). These findings highlight the importance of using continuous ECG analysis when studying volatile anaesthetic agents in young children.
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Randomized Controlled Trial Comparative Study Clinical Trial
Intravenous opioids reduce airway irritation during induction of anaesthesia with desflurane in adults.
Desflurane is not used for the induction of anaesthesia despite its favourable pharmacokinetic characteristics because it causes airway irritation. We investigated whether pretreatment with i.v. narcotics reduced unwanted effects. One hundred and eighty adults were randomized to three groups (60 per group) to receive i.v. saline, fentanyl 1 microgram kg-1 and morphine 0.1 mg kg-1, respectively, before inhalational induction with desflurane in nitrous oxide and oxygen. ⋯ Laryngospasm developed in 11.7% of controls compared with 3.3 and 1.7% in the fentanyl and morphine groups, respectively. More patients in the control group had excitatory movements (46.7%) than in the fentanyl (16.7%) and morphine (8.3%) groups. These results demonstrate that i.v. opioids reduce airway irritability significantly during inhalational induction with desflurane in adults.
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The aim of this study was to validate measurements of intraoperative left ventricular (LV) area by transoesophageal echocardiography against simultaneous measurements of LV volume by conductance catheter (CC) in cardiac surgical patients with normal systolic LV function. Echo area was compared with CC volume during steady state and during acute changes of pre- and afterload by partial clamping of the inferior vena cava and the ascending aorta in eight patients scheduled for coronary artery bypass grafting. ⋯ Intraoperative area measurements with transoesophageal echocardiography in cardiac surgical patients with normal systolic LV function show good correlation with CC volume measurements under steady-state conditions. During acute unloading by vena cava occlusion, the resulting small end-systolic echo area measurements differ significantly more from CC volume measurements than during acute increase in afterload by aortic occlusion.