British journal of anaesthesia
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Randomized Controlled Trial Clinical Trial
Use of i.m. ranitidine for the prophylaxis of aspiration pneumonitis in obstetrics.
Twenty patients who underwent elective Caesarean section received ranitidine 150 mg by mouth 8-14 h, and 50 mg i.m. 90 min, before surgery. Intraoperative gastric aspiration resulted in contents with a pH greater than 2.5 and volume less than 25 ml in all patients (mean pH 6.5 (SD 0.8); mean volume 9.0 (SD 7.2) ml). Sixty patients in labour, who received ranitidine 50 mg i.m. 6-hourly, underwent emergency surgery. ⋯ Ranitidine medication resulted in a mean aspirated gastric volume of 31.4 (26.6) ml and pH of 5.3 (2.1); five of 30 patients had a pH less than 2.5. The addition of sodium citrate 0.3 mol litre-1 resulted in gastric pH greater than 2.5 in all patients and a mean gastric volume of 43.2 (38.3) ml. The group who received only sodium citrate 0.3 mol litre-1 had a mean pH of 5.3 (1.1) and a mean volume 122.7 (98.2) ml.
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Using an in vitro nerve preparation, we have studied the relative electrophysiological properties of myelinated and unmyelinated nerve fibres in the vagus nerve of 1-, 9- and 36-month-old rabbits and their sensitivity to local anaesthetic. The baseline (values before infusion of local anaesthetic) mean amplitude and conduction velocity (CV) of the compound action potential (APc) were recorded and the nerve was exposed to a range of concentrations (0.5-4.0 mmol litre-1) of lignocaine for periods sufficient to attain equilibrium block. There was an increase in the amplitude of the A fibre elevation from the 1-month to the 9- and 36-month-old rabbits. ⋯ The ED50 values of lignocaine for reduction of the A fibre elevation in the 1-, 9- and 36-month-old rabbits were 0.66, 0.94 and 0.85 mmol litre-1, respectively. The respective values for the B fibres were 0.74, 1.21 and 0.82 mmol litre-1, while those of the C fibres were 1.50, 2.44 and 2.07 mmol litre-1. In general, nerves from young and old rabbits were more sensitive to local anaesthetic-induced conduction blockade, suggesting that smaller doses of local anaesthetic are required clinically for anaesthesia in paediatric and older age groups.
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Randomized Controlled Trial Clinical Trial
Changes in pupil diameter after oral administration of codeine.
Pupillary constriction occurs following administration of opioids and may be used as a marker of opioid activity. We have measured plasma concentrations and pupil diameters in 16 healthy volunteers after the oral administration of placebo or codeine. Pupil size decreased significantly after codeine compared with placebo. Pupil size was related to the plasma concentrations of codeine (P less than 0.05).
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Randomized Controlled Trial Clinical Trial
Use of the post-tetanic count to monitor recovery from intense neuromuscular blockade in children.
The post-tetanic count was investigated as a method of monitoring intense neuromuscular blockade in children. One of five myoneural blockers (atracurium, vecuronium, pancuronium, tubocurarine or alcuronium) was given to groups of six children during nitrous oxide-oxygen-halothane anaesthesia. ⋯ The interval between the appearance of the first post-tetanic response and the first train-of-four response was typically 5-10 min for the intermediate-acting agents vecuronium and atracurium, and 20-30 min for the long-acting agents pancuronium, alcuronium and tubocurarine. A post-tetanic count of 6 with alcuronium and tubocurarine, or 7 with vecuronium, atracurium and pancuronium indicated that recovery of the first train-of-four response was imminent.
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Comparative Study
Clinical pharmacology of mivacurium chloride (BW B1090U) infusion: comparison with vecuronium and atracurium.
Mivacurium chloride (BW B1090U) is a new, short-acting non-depolarizing neuromuscular blocking agent. It is a synthetic bis-benzylisoquinolinium diester, which is hydrolysed rapidly by plasma cholinesterase. This study compares mivacurium, atracurium and vecuronium by continuous i.v. infusion. ⋯ For vecuronium, corresponding recovery times were 13.8 (0.9) and 32.0 (1.2) min, respectively. Comparative recovery times for mivacurium were 40-50% of those for vecuronium. There was a significant correlation between the infusion rate of mivacurium required to maintain 95% twitch depression and the plasma cholinesterase activity of individual subjects.