British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial
Sedation for fibreoptic gastroscopy: a comparative study of midazolam and diazepam.
Midazolam, a water-soluble benzodiazepine, was compared with diazepam in fat emulsion (Diazemuls) as sedation for outpatient gastroscopy in a randomized double-blind fashion. Midazolam 0.05 mg kg-1 was found to be approximately equipotent to Diazemuls 0.15 mg kg-1. There were no differences concerning speed of recovery and all patients were considered ready for discharge after 2 h. ⋯ With the same degree of sedation, midazolam produced a higher frequency of amnesia (60% v. 7%; P less than 0.001) for the endoscopic procedure. Although the patients appeared to prefer midazolam to Diazemuls, this difference was significant only in patients who had not previously undergone gastroscopy (P less than 0.05). The high degree of amnesia with midazolam may be an advantage in sedation for unpleasant procedures like gastroscopy.
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Randomized Controlled Trial Comparative Study Clinical Trial
Comparison of effects of intraoperative and postoperative methadone: acute tolerance to the postoperative dose?
The effects of methadone 10 mg administered in two different clinical contexts, at induction of anaesthesia and following operation, were studied in two groups of patients undergoing elective total hip replacement. The intraoperative group received methadone 10 mg i.v. at induction of anaesthesia as part of a balanced anaesthetic technique. The postoperative group received methadone 10 mg i.v. following operation, extradural bupivacaine being used for the operative period. ⋯ Subsequently, the postoperative group had a significantly greater analgesic requirement which resulted in significantly greater plasma methadone concentrations the following morning. Thus, the administration of methadone following operation appeared to exert less analgesic effect than the same dose given during operation. The reasons for this are discussed.
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Plasma concentrations of etomidate have been measured in six patients who required intermittent positive pressure ventilation following surgery. There was an approximately linear relationship between the plasma concentration and the rate of infusion of etomidate. ⋯ The decrease in the plasma concentration after discontinuing the infusion was consistent with a three-compartment pharmacokinetic model. The plasma terminal half-life was found to be about 5.5 h, and the clearance calculated to be 0.025 litre kg-1 min-1.
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This article reviews the actions of general anaesthetics on synapses in the mammalian central nervous system. It is shown that during general anaesthesia, anaesthetics act primarily on the chemical transmission process itself and do not affect the conduction of impulses in nerve axons or change the electrical excitability of neurones. ⋯ In addition to these effects on the neurosecretory process, anaesthetics directly affect the sensitivity of the postsynaptic receptors to transmitter substances, although the effects vary between anaesthetics and receptors. It is concluded that general anaesthesia results from a summation of a number of effects which together tend to depress the excitability of the CNS as a whole.