British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Postoperative analgesia by continuous extradural infusion of bupivacaine and diamorphine.
Three solutions administered by continuous extradural infusion for postoperative analgesia were compared in a randomized, double-blind manner. All patients underwent major abdominal gynaecological surgery and received 0.125% bupivacaine in 0.9% saline, diamorphine in 0.9% saline (0.5 mg in 15 ml) or diamorphine mixed with 0.125% bupivacaine (0.5 mg in 15 ml), at a rate of 15 ml h-1. The bupivacaine-diamorphine mixture provided significantly superior analgesia compared with either bupivacaine or diamorphine alone. No major side effects were encountered.
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Alfentanil was administered, together with midazolam, as part of a total i.v. anaesthetic technique. The pharmacokinetics of alfentanil were determined in 10 female patients undergoing lower abdominal surgery. The dose regimen of alfentanil, based on simulation studies, consisted of a two-stage infusion following an initial bolus dose. ⋯ Neither lower abdominal surgery nor the simultaneous administration of midazolam seemed to affect the kinetics of alfentanil as compared with results from studies in healthy volunteers. The short half-life of alfentanil, resulting from a small volume of distribution, makes it suitable as part of a total i.v. technique. Consideration must be paid, however, to interindividual differences in the pharmacodynamic response and in plasma clearance.
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Comparative Study
Decontamination of halothane from anaesthetic machines achieved by continuous flushing with oxygen.
The contamination of four types of anaesthetic machine with halothane was sequentially sampled by mass spectrometry while the machines were continuously flushed with oxygen 8 litre min-1 for up to 24 h. Contamination decreased in an exponential manner. Machines fitted with Selectatec vaporizer mounting systems and with the vaporizer removed showed contamination less than 0.02 parts per million (p.p.m.) of halothane after 12 h flushing. ⋯ Background contamination concentrations of greater than 0.05 p.p.m. were measured in a patient-free recovery area of an operating theatre suite. Concentrations increased to 1 p.p.m. when patients were admitted following halothane anaesthesia. Decontamination of anaesthetic machines to concentrations of halothane below those detected as background contamination within recovery areas may allow such machines to be used safely to anaesthetize patients at risk from halothane.
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Randomized Controlled Trial Clinical Trial
Postoperative analgesia with fentanyl: pharmacokinetics and pharmacodynamics of constant-rate i.v. and transdermal delivery.
We have investigated the use of constant-rate delivery of fentanyl by i.v. and transdermal routes for the treatment of pain after major surgery. Forty-five males, ASA I-III, received in a double-blinded fashion either placebo (n = 6) or fentanyl (n = 39) i.v. at one of four dose rates (25, 50, 100 or 125 micrograms h-1). Stable serum concentrations of fentanyl were produced by the end of surgery and were maintained for a total of 24 h. ⋯ Post-operative morphine requirements were minimal (less than 0.5 mg h-1) and PaCO2 remained acceptable in all patients. Serum concentrations of fentanyl increased slowly (15 h to plateau) and decreased slowly (apparent half-life, 21 h). We conclude that delivery of analgesic doses of fentanyl is feasible by the transdermal route.
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The effects of halothane, isoflurane and enflurane were compared on three CNS excitatory synaptic pathways in vitro, to determine whether selective actions described in vivo result from differential effects on anatomically distinct cortical pathways and neurone populations. Halothane (0.25-1.25 vol%) depressed postsynaptic excitability of CA1 pyramidal neurones in response to activation of stratum radiatum synaptic inputs, and concentration-dependent excitatory (0.25-1.25 vol%) and depressant (1.5-2.0 vol%) actions were observed on dentate granule neurone excitability and perforant path evoked synaptic responses. In contrast, isoflurane increased CA1 neurone excitability (0.25-0.75 vol%) and produced postsynaptic depression of dentate neurones (0.5-4.0 vol%). ⋯ Differential actions were also observed for the three anaesthetics on stratum oriens excitatory inputs to CA1 neurones, and on antidromic responses. A good correlation (r = 0.992) exists between the membrane/buffer partition coefficients of these anaesthetics and their half-maximal concentrations for depression of synaptic responses; however, this correlation does not reflect the different, anaesthetic-specific actions observed. The results indicate that inhalation anaesthetics act at multiple and selective hydrophobic recognition sites which are heterogenously distributed on different synaptic pathways.