British journal of anaesthesia
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Atracurium has been evaluated in anaesthetized patients using the single twitch and tetanic responses of the adductor pollicis muscles. I.v. doses of 0.3-0.9 mg kg-1 produced complete neuromuscular block. In the dose range used mean arterial pressure was only decreased by about 20% of control for a few minutes after 0.9 mg kg-1 which was three times the standard dose. ⋯ Intubation of the trachea could be accomplished when blockade of the tetanic response was complete and at a time when the single twitch was only slightly depressed. It was concluded that the tetanic response provided a more accurate assessment of the time-course of neuromuscular blockade than the single twitch. Infusion studies demonstrated that recovery from full neuromuscular blockade after a 30- or 60-min infusion was as rapid as that after bolus doses of atracurium 0.3-0.9 mg kg-1 and this could be regarded as further evidence of the lack of cumulative effects.
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Comparative Study Clinical Trial Controlled Clinical Trial
Muscular relaxation with atracurium, vecuronium and duador under balanced anaesthesia.
The neuromuscular effects of three new nondepolarizing neuromuscular blocking drugs, atracurium, vecuronium and Duador, were investigated in surgical patients under balanced anaesthesia. (The numbers of patients in each study are given in the tables.) There were no significant differences in the neuromuscular effects of the three agents. None showed any cumulation after repeated administration of maintenance doses. Muscular relaxation for upper abdominal surgery was adequate as long as the isometric twitch tension (P) was no more than 25% of control. ⋯ The initial dose of Duador caused a 16.7% increase in heart rate. The findings indicate that the three new muscle relaxants merit further clinical trial. In our opinion, until the results of such studies become available, atracurium should not be used in patients with a history of allergic diathesis and Duador in those in whom increased heart rate may be harmful.
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Conditions for endotracheal intubation provided by different dose regimens of atracurium 0.4 mg kg-1 and 0.5 mg kg-1 were studied and compared with each other and with suxamethonium 1.0 mg kg-1. Intubation was attempted at 2.5, 2 min and 1.5 min following a bolus dose of atracurium, and 1 min following suxamethonium. ⋯ Atracurium, when administered 5 min following recovery from a suxamethonium-induced block, had a significantly faster onset of neuromuscular blockade (P less than 0.01) than the onset observed following atracurium alone. Administration of atracurium 0.42 mg kg-1 3 min after an initial dose of 0.08 mg kg-1 of the drug produced a significantly more rapid onset of block when compared with a bolus dose of 0.5 mg kg-1 (P less than 0.02).
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Comparative Study
Ventilatory effects during and after continuous infusion of fentanyl or alfentanil.
The opioid drugs fentanyl and alfentanil were infused at a constant rate as supplements to nitrous oxide in oxygen anaesthesia throughout the period of surgery. These infusions were continued into the period after operation for 1 h after the discontinuation of anaesthesia. Continuous infusion of alfentanil 20 micrograms kg-1 h-1 and fentanyl 3 micrograms kg-1 h-1 resulted in depression of the carbon dioxide response curve with a lesser effect on frequency and minute ventilation. One hour after discontinuing the infusions the degree of ventilatory depression was only marginally less with fentanyl, but considerably less with alfentanil, reflecting the shorter terminal half-life of that drug.
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The antagonistic action of a bolus dose of edrophonium 0.75 mg kg-1 on the neuromuscular blockade induced by atracurium was studied in 10 patients anaesthetized with nitrous oxide and narcotic supplements. The reversal agent was administered when the twitch height had recovered spontaneously to approximately 20% of control. ⋯ Clinically adequate reversal (train-of-four ratio of 75% or better) was achieved 6.6 +/- 1.5 min following injection of the edrophonium and there was no evidence of subsequent muscle weakness. The possible advantages of the clinical use of edrophonium in producing a rapid reversal of atracurium blockade are discussed.