British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Effect of ondansetron on nausea and vomiting after middle ear surgery during general anaesthesia.
The efficacy of ondansetron 4 mg and 8 mg was compared with placebo in the reduction of postoperative nausea, retching and vomiting (PONV) after middle ear surgery during general anaesthesia, in 75 patients, in a double-blind and randomized study. Both doses of ondansetron were predictors for a decrease in PONV and the number of doses of rescue antiemetic needed per patient (droperidol: from 0.72 in the placebo group to 0.32 in both the 4-mg and 8-mg groups). No reduction in PONV was observed in patients with a history of motion sickness, whereas in patients without a history of motion sickness, ondansetron reduced both the proportion of patients suffering from PONV from 53% to 20% (P < 0.05) and of those needing droperidol from 53% to 17% (P < 0.05).
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Randomized Controlled Trial Clinical Trial
Time course of potentiation of mivacurium by halothane and isoflurane in children.
We studied 40 children, aged 1-15 yr, to analyse the time course of potentiation of mivacurium produced by halothane and isoflurane. A steady infusion requirement of mivacurium to maintain 90% neuromuscular block was established during thiopentone-alfentanil-nitrous oxide-oxygen anaesthesia. ⋯ Both volatile agents decreased the infusion requirements of mivacurium in an exponential manner in that maximal potentiation occurred only after 30-80 min. Maximal reduction in infusion rate (32% in group Hal and 70% in group Iso; P < 0.0001) did not depend on the age of the child but became established sooner the younger the child in the case of isoflurane (P = 0.002).
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The mechanism by which racemic (R(+/-)) ketamine relaxes airway smooth muscle is unclear and there is no information on the differential effects of ketamine and its isomers. In this study, we have examined the spasmolytic effect of R(+/-) ketamine and its isomers S(+) and R(-) ketamine and the role of intracellular calcium and opioid receptors in R(+/-) ketamine-induced relaxation. The tension of isolated guinea pig tracheal strips was measured isometrically with a force displacement transducer and contraction elicited with histamine 10(-5) mol litre-1. ⋯ We conclude that although both ketamine isomers produced equipotent spasmolytic effects on airway smooth muscle precontracted with histamine, they differed in their ability to potentiate the relaxing effect of adrenaline. S(+) ketamine produced the greatest potentiation. Changes in intracellular Ca2+ level secondary to a reduction in the L-type Ca2+ current may partially mediate the spasmolytic effect of R(+/-) ketamine.
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Case Reports
Sudden onset of subarachnoid block after subdural catheterization: a case of arachnoid rupture?
We describe a patient who received an apparently uneventful extradural block in labour but developed rapid extension of neural block within minutes of receiving her first incremental dose 2 h later. Computed contrast tomography revealed radio-opaque dye within both the subdural and subarachnoid spaces, but none within the extradural space. This case report demonstrates that subdural spread of low-dose local anaesthetics is not always clinically distinguishable from extradural analgesia and that the arachnoid membrane may subsequently perforate with potentially serious consequences.
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We have reviewed randomized controlled trials to assess the effectiveness and safety of anaesthetics which omitted nitrous oxide (N2O) to prevent postoperative nausea and vomiting (PONV). Early and late PONV (6 and 48 h after operation, respectively), and adverse effects were evaluated using the numbers-needed-to-treat (NNT) method. In 24 reports with information on 2478 patients, the mean incidence of early and late vomiting with N2O (control) was 17% and 30%, respectively. ⋯ Omitting N2O had no effect on complete control of emesis or nausea. The NNT for intraoperative awareness with a N2O-free anaesthetic was 46 compared with anaesthetics where N2O was used. This clinically important risk of major harm reduces the usefulness of omitting N2O to prevent postoperative emesis.