Anaesthesia
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The accuracy of a computer-controlled infusion of midazolam, based on previously published pharmacokinetic parameters, was tested prospectively in 12 adult female patients undergoing general anaesthesia. Anaesthesia consisted of an initial bolus followed by an exponentially decreasing infusion of midazolam given according to body weight, fentanyl, nitrous oxide and vecuronium. Venous blood samples were taken at 15 min-intervals throughout the procedures and for 1-2 h postoperatively. ⋯ Retrospective fitting of an alternative set of published parameters for midazolam resulted in significant deterioration of the model. The precision was similar to that found in past studies of intravenous anaesthetic agents. Further improvement in the accuracy of midazolam infusion awaits improved understanding of the causes of pharmacokinetic variability.
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Comparative Study
Comparison of recovery index of rocuronium or vecuronium with simultaneously administered pancuronium in the isolated forearm.
A series of isolated forearm experiments is described in which rocuronium or vecuronium were injected into one arm, and pancuronium injected simultaneously into the contralateral arm. The time for 25%-75% twitch recovery (recovery index) was recorded in both arms. The recovery indices of rocuronium and vecuronium were similar, but that of pancuronium significantly longer. Because the recovery indices compared in any one experiment occurred in the presence of identical background plasma concentration, the differences observed in recovery index between pancuronium and either rocuronium or vecuronium are due to different rates of dissociation from the effect compartment at the neuromuscular junction.
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The ability of a target-controlled propofol infusion system to provide sedation for 40 patients undergoing surgery under regional blockade was assessed. Eighty-eight per cent of the total infusion time was at the desired sedation level with little oversedation. ⋯ The pharmacokinetic algorithm performed as well when used for sedation as for total intravenous anaesthesia. The predicted and measured blood propofol concentrations showed a bias of -12% and a precision of 34%.
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The management of a patient who required positive pressure ventilation following pharyngolaryngo-oesophagectomy during which tracheal injury was sustained is described. Ventilation with a tracheal tube resulted in a massive pneumoperitoneum. Bilateral bronchial intubation was employed with success.
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Sixty adult patients following general surgical operation were treated with patient-controlled analgesia using morphine. Patients were allocated into three groups to receive: no background infusion, a 1 mg.h-1 or a 2 mg.h-1 background infusion. The other controls on the patient-controlled analgesia machine were set to allow a maximum dose of morphine of 6 mg.h-1 to each group. ⋯ Patients who received a background infusion of 2 mg.h-1 had an increased incidence of nausea (p < 0.05). A background infusion of 1 mg.h-1, with a 1 mg bolus dose and a 12 min lockout interval provided acceptable pain relief without excessive nausea. In all three groups the ratio of analgesic requests to successful deliveries correlated with the degree of pain reported by visual analogue score (p = 0.0001).