British journal of anaesthesia
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We have examined the phenotypic expression of several parameters associated with malignant hyperthermia (MH) susceptibility in three groups (homozygous normal, homozygous abnormal and heterozygous) of Yorkshire/Duroc swine genotyped by a mutation in the ryanodine receptor. Subgroups of homozygous abnormals were classified further by the appearance or absence of muscle rigidity on prolonged in vivo challenge with halothane and suxamethonium. Four swine heterozygous for the proposed MH mutation were indistinguishable from five homozygous normal swine in temperature, heart rate, lactate concentrations, base excess and pH determined during the prolonged halothane and suxamethonium challenge. ⋯ Therefore, inheritance of only one allele carrying the defect in the ryanodine receptor does not significantly alter phenotypes associated with MH susceptibility in this strain of swine. As four swine homozygous for the proposed MH defect did not exhibit rigidity and three of these had no other signs of MH on prolonged halothane and suxamethonium challenge, we conclude that the reported mutation in the ryanodine receptor may be necessary, but is not sufficient, for consistently eliciting the malignant hyperthermia syndrome. These findings suggest that a modulator of the syndrome may explain variability within individuals in human MH.
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Randomized Controlled Trial Clinical Trial
Synergism between atracurium and vecuronium in children.
In 30 children under balanced anaesthesia, we have determined dose-response curves and maintenance requirement of three dose ratio combinations of atracurium and vecuronium (10:1, 4:1 or 1.6:1 on a microgram:microgram basis). Neuromuscular block was monitored by adductor pollicis EMG. An equipotent dose ratio (4:1) was most potent, with a mean (SEM) ED95 of atracurium 95 (6) micrograms kg-1 with vecuronium 24 (1) micrograms kg-1. ⋯ These results indicate that a combination of atracurium and vecuronium is supra-additive compared with the effects of each drug alone. However, all combinations maintained an intermediate character of neuromuscular block. Combining atracurium with vecuronium may reduce drug requirement by 40%.
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Randomized Controlled Trial Clinical Trial
Patient-controlled analgesia with a mixture of morphine and droperidol.
In a prospective study, 50 women who had undergone uncomplicated abdominal hysterectomy under general anaesthesia were allocated randomly to receive patient-controlled analgesia with either morphine alone or a mixture of morphine and droperidol. Bolus doses of morphine 1 mg and droperidol 0.05 mg were used with a lockout time of 5 min. During the first 24 h after surgery the mean (range) dose of droperidol in the droperidol group was 3.2 (1.9-6.0) mg. ⋯ In the morphine alone group, 19 patients required additional antiemetic therapy, whereas in the droperidol group only one patient found this necessary (P < 0.001). Extrapyramidal side effects were not observed in any patient. Significantly more patients were of the opinion that PCA had provided excellent analgesia when droperidol had been used (P < 0.01).
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We gave equal groups of rabbits seven extradural (500 micrograms kg-1) or intrathecal (250 micrograms kg-1) injections of bupivacaine, at 24-h intervals. A decrease in the duration of motor block was observed after the extradural injections. ⋯ An additional regimen was tested in which five doses of bupivacaine 125 micrograms kg-1 were administered intrathecally after a loading dose of 250 micrograms kg-1, when the animals showed partial recovery from the previous dose; there was no decrease in the effect. The absence of tolerance to intrathecal bupivacaine implies that tachyphylaxis to extradural local anaesthetics results from a decrease in availability of the drug to the neural target, rather than a diminution in effect at the site of action.