• R V Miguel, I K Barlow, and D L Dombrowski.
• Department of Anesthesiology, University of South Florida College of Medicine, Tampa.
• J Clin Anesth. 1994 Mar 1;6(2):106-9.

Study ObjectiveTo examine how priming with ED10 d-tubocurarine prior to the administration of ED95 vecuronium bromide affects onset and duration of neuromuscular blockade.DesignProspective, randomized, observer-blinded study.SettingOperating room at a university cancer center.Patients40 ASA physical status I and II patients undergoing ambulatory surgical procedures.InterventionsPatients were randomized to one of two groups. Group 1 patients received d-tubocurarine 50 micrograms/kg intravenously (IV), followed by vecuronium 60 micrograms/kg IV. Group 2 patients received vecuronium 60 micrograms/kg IV without priming. All patients received a total IV anesthetic consisting of alfentanil and propofol for induction of anesthesia and propofol alone for maintenance of anesthesia.Measurements And Main ResultsOnset of muscle relaxation was determined with an electromyograph (Datex Relaxograph), documenting time to 80% depression of the first twitch in a train-of-four (T(1)80%), percent depression of T1 at 60 and 90 seconds (T(1)60 and T(1)90, respectively), T4:T1 ratio at 90 seconds, and time to achieve maximal blockade (Bmax). Recovery was evaluated by measuring the time required for return of T1 to 25% of the baseline value. Intubating conditions were assessed at 90 seconds after vecuronium administration and graded on a 1 (jaw tight, impossible to intubate) to 4 (jaw relaxed, vocal cords immobile) scale. All criteria measuring onset of neuromuscular blockade (i.e., T(1)80%, T(1)60, T(1)90, T4:T1, and Bmax) were significantly shorter (p < 0.05) in patients who received d-tubocurarine. Recovery was similar in both groups. Intubation scores were significantly better 90 seconds after priming (p < 0.05).ConclusionsThese results indicate that crossover dosing of nondepolarizing muscle relaxants may have synergistic effects. Priming with ED10 d-tubocurarine prior to an ED95 dose of vecuronium shortens the time to 80% T1 depression and produces satisfactory intubating conditions at 90 seconds, without prolonging the duration of the Therefore, d-tubocurarine is an attractive drug for priming vecuronium in short operative procedures that require muscle relaxation.

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