British journal of anaesthesia
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Comparative Study
Evaluation of cumulative properties of three new nondepolarizing neuromuscular blocking drugs BW A444U, atracurium and vecuronium.
Comparative patterns of recovery during successive doses of three new, relatively non-cumulative, intermediate-duration non-depolarizing neuromuscular blocking drugs, BW A444U, atracurium (BW33A) and vecuronium (Org NC 45), were studied in 94 surgical patients during thiopentone in nitrous oxide and oxygen with narcotic anaesthesia. The train-of-four (TOF) pattern of nerve stimulation was used. The spontaneous 5-25% recovery time of the first twitch of TOF showed a statistically significant difference between the initial dose and the fifth incremental dose in the cases of atracurium and vecuronium, but not in the case of BW A444U. ⋯ The difference was significant only when the final dose of vecuronium was compared with the initial dose (TOF ratio 79.3 +/- 2.3% v. 64.3 +/- 4.4%; P less than 0.005). Analysis of variance indicates that the TOF ratio at 95% recovery of the first twitch of TOF after the final dose of vecuronium (64.3%) is significantly smaller (P less than 0.001) than that of either BW A444U (78%) or atracurium (84%), indicating that vecuronium appears to show more residual fade and greater cumulative effect after incremental doses than BW A444U or atracurium. The data suggest that the cumulative properties of the new drugs may be ranked as follows: atracurium less than BW A444U less than vecuronium.
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Comparative Study
Neuromuscular and cardiovascular effects of atracurium during nitrous oxide-fentanyl and nitrous oxide-isoflurane anaesthesia.
The neuromuscular and cardiovascular effects of atracurium were compared during nitrous oxide-isoflurane and nitrous oxide-fentanyl anaesthesia in healthy surgical patients. The dose-response curve was shifted significantly to the left during nitrous oxide-isoflurane anaesthesia (ED50 0.068 mg kg-1) as compared with nitrous oxide-fentanyl anaesthesia (ED50 0.083 mg kg-1). For equipotent doses, the time course of neuromuscular effects (onset and duration) was not appreciably different between the nitrous oxide-isoflurane group and the nitrous oxide-fentanyl group. ⋯ The onset time (time from injection to peak effect) for subparalytic doses of atracurium was approximately 6.5 min and is comparable to the onset time for equipotent doses of pancuronium and vecuronium. The duration of neuromuscular effects of atracurium (time from injection to 95% recovery) was approximately 20 min for subparalytic doses and is the same as that of vecuronium and one-third to one-half that of pancuronium. It is concluded that the peak effect of atracurium is enhanced more by nitrous oxide-isoflurane than by nitrous oxide-fentanyl anaesthesia, but for equipotent doses the time-course is the same.
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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.