British journal of anaesthesia
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The pattern of ventilation was studied in eight healthy male volunteers breathing, in sequence, air and then two subanaesthetic concentrations of nitrous oxide (20% and 40%). The effect of these gas mixtures on the response to an added inspiratory resistance (3.88 kPa litre-1s-1) was examined. During unrestricted breathing of 40% nitrous oxide, there was a significant decrease (P less than 0.05) in inspiratory time (TI), a concomitant increase in the rate of ventilation and a significant decrease (P less than 0.05) in the end-tidal carbon dioxide tension (PE'CO2) compared with air breathing. ⋯ TI, VT, minute volume and PE'CO2 were similar for each gas mixture during steady state breathing against resistance. The increase in PE'CO2 when breathing 40% nitrous oxide against the resistance represented a significant (P less than 0.01) difference in response to the load compared with that breathing air. There was no significant change in these variables when breathing 20% nitrous oxide.
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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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Clinical Trial Controlled Clinical Trial
Spinal anaesthesia for caesarean section. The use of 0.5% bupivacaine.
Subarachnoid anaesthesia was induced with 0.5% bupivacaine 2-3.5 ml in 33 women scheduled for elective Caesarean section. Three patients failed to develop adequate analgesia with bupivacaine but were managed satisfactorily with heavy cinchocaine. All the other patients developed adequate analgesia eventually. Since the spread of analgesia was uniquely dependent on posture a new hypothesis is presented to explain the distribution of intrathecal anaesthetic drugs in late pregnancy.
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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.