British journal of anaesthesia
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The effect on intervillous blood flow of lumbar extradural analgesia for Caesarean section was studied in nine healthy women using xenon-133. Extradural anaesthesia was performed with lignocaine 1 1/2% 16--20 ml with adrenaline 5 microgram ml-1. Impairment of placental blood flow during the block was observed in seven patients, but the mean decrease (13% from the control value) was not statistically significant. The most notable decrease in intervillous blood flow occurred in two patients with simulateous arterial hypotension.
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The plasma concentrations of pancuronium were monitored during i.v. infusions of the relaxant in dogs. Pancuronium was administered at rates which maintained the degree of neuromuscular blockade at three predetermined levels. The concentrations of the drug in the blood were consistent for any one animal but showed considerable overlap for the three levels of paralysis between animals. ⋯ The concentrations at 80% of control were 0.094 microgram ml-1 and 0.083 microgram ml-1 respectively. The agreement between these results suggests a relationship between the plasma concentration of the relaxant and its effect during the termination of the action after a large bolus injection of the drug. As this occurs chiefly during the postdistribution equilibrium, the relatively slow decrease in plasma concentration would appear to become the rate-limiting factor in recovery from paralysis.
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The effects of bilateral adrenalectomy, together with the i.v. administration of bretylium tosylate 20 mg kg-1 on halothane-induced malignant hyperthermia (MH), were investigated in six Pietrain pigs. All six animals survived the halothane challenge, and failed to show any signs of increased muscle metabolism. Bilateral adrenalectomy alone prevented halothane-induced MH in three out of four Pietrain pigs, whereas the i.v. administration of bretylium alone protected only one pig out of an additional four animals studied. The results show that complete adrenergic blockade inhibits the susceptibility of Pietrain skeletal muscle to halothane and that the adrenal medulla makes an important contribution to this response.