British journal of anaesthesia
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We investigated the relationship between the latency of the Nb wave of the auditory evoked response (AER) and periods of awareness during propofol anaesthesia. In the anaesthetic room before cardiac surgery the AER was recorded continuously in 14 patients. Awareness was measured by the ability of the patient to respond to command using the isolated forearm technique (IFT). ⋯ None of the patients had any recollection of events after the initial induction of anaesthesia as measured by explicit and implicit memory tests. These results suggest that the Nb latency of the AER may represent an indication of awareness in individual patients, but wide inter-patient variability limits its practical usefulness. In addition, because no evidence of memory was demonstrated, even when patients were known to be awake, the relationship between AER and memory processing remains unclear.
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Many indices are used to quantify pulmonary oxygen transfer. Indices that use only measurements from arterial blood and inspired gas assume a constant C(a-v)O2. Though variations in C(a-v)O2 are recognized, indices such as PaO2/FIO2 remain popular and are often considered the best measure of pulmonary oxygen transfer in critically ill patients. ⋯ At an FlO2 of 0.7, PaO2 /FIO2 varied between 18 and 10 kPa and at an FIO2 of 0.9 the ratio varied between 22 and 8 kPa. These changes, which were unrelated to underlying lung pathology, are sufficiently large to result in misclassification on the gas exchange scale suggested by the American European Consensus Conference on ARDS. This study shows there is no reliable alternative to Qs/Qt to quantify pulmonary oxygen transfer in critically ill patients.
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Randomized Controlled Trial Clinical Trial
Analgesic efficacy of tramadol 2 mg kg(-1) for paediatric day-case adenoidectomy.
We studied the analgesic efficacy of tramadol 2 mg kg(-1) for post-operative analgesia after day-case adenoidectomy in children aged 1-3 yr. Eighty children were allocated randomly to receive tramadol 2 mg kg(-1) i.v. or placebo immediately after induction of anaesthesia. Anaesthesia was induced with alfentanil 10 microg kg(-1) and propofol 4 mg kg(-1) followed by mivacurium 0.2 mg kg(-1) for tracheal intubation. ⋯ Forty-five per cent of children receiving tramadol did not require post-operative analgesia at all compared with 15% of children receiving placebo (P = 0.003). Recovery times and the incidence of adverse effects were similar in the two groups in the recovery room and at home. The requirement for rectal ibuprofen at home did not differ between groups.
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Randomized Controlled Trial Clinical Trial
Effects of fentanyl, alfentanil, remifentanil and sufentanil on loss of consciousness and bispectral index during propofol induction of anaesthesia.
The bispectral index (BIS) and a sedation score were used to determine and compare the effect of propofol in the presence of fentanyl, alfentanil, remifentanil and sufentanil. Seventy-five non-premedicated patients were assigned randomly into five groups (15 in each) to receive fentanyl, alfentanil, remifentanil, sufentanil or placebo. Opioids were administered using a target-con-trolled infusion device, to obtain the following predicted effect-site concentrations: fentanyl, 1.5 ng ml(-1); alfentanil, 100 ng ml(-1); remifentanil, 6 ng ml(-1); and sufentanil, 0.2 ng ml(-1). ⋯ The relationship between propofol effect-site concentration and BIS was preserved with or without opioids. In the presence of an opioid, LOC occurred at a lower effect-site concentration of propofol and at a higher BIS50 (i.e. the BIS value associated with 50% probability of LOC), compared with placebo. Although clinically the hypnotic effect of propofol is enhanced by analgesic concentrations of mu-agonist opioids, the BIS does not show this increased hypnotic effect.