British journal of anaesthesia
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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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The effects of halothane and of prior administration of suxamethonium on atracurium neuromuscular blockade have been investigated. Halothane potentiated the intensity of block produced by atracurium 0.1 or 0.15 mg kg-1. Duration of block was prolonged (27%) by halothane with a small dose of atracurium (0.15 mg kg-1) and was also prolonged (29%) with larger doses of atracurium (0.4 mg kg-1). Prior suxamethonium 1 mg kg-1 increased the intensity of block after atracurium 0.15 mg kg-1 from 52% (control) to 84%, but caused minimal change in duration of atracurium blockade.
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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.
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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.