Anaesthesia
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Measurements of the vapour concentrations delivered by the EMO and Oxford Miniature Vaporizers (OMV) were made with both continuous (plenum mode) and intermittent (drawover mode) air flows. Leakage of ether, halothane and trichloroethylene vapours through the corrugated elephant tubing was also measured. Both vaporizers performed most consistently with the intermittent flows for which they were designed. ⋯ Minimal amounts of ether were lost through the tubing but halothane losses were appreciable, while losses of trichloroethylene were enough to reduce the concentrations available to the patient. The EMO is not suitable for plenum use with carrier gas flows below about 10 litres/min. The OMV is a useful plenum vaporizer although the outputs are generally lower than indicated at higher flows.
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The effect of the administration of fentanyl 50 micrograms/kg body weight on the established metabolic response to pelvic surgery was investigated. In comparison with a control group of patients in whom anaesthesia was supplemented with halothane, fentanyl was associated with a significant decrease in only blood lactate concentrations and heart rate. There were no significant differences in blood glucose, plasma non-esterified fatty acids, and plasma cortisol values between the two anaesthetic techniques. It is concluded that the administration of high-dose fentanyl has little effect on the established metabolic response to surgery, compared with the marked changes observed when the same dose is given before the onset of surgical stimulation.