Potentiation of atracurium by pancuronium during propofol-fentanyl-N2O anesthesia.

At the end of abdominal surgery deep neuromuscular blockade is required for peritoneal closure. Ideally injecting an intermediate acting drug like atracurium after a long acting drug such as pancuronium should deepen the neuromuscular block without the fear of an inadequate reversal at the completion of surgery. Thirty patients ASA I or II status, without known allergy to myorelaxant and without neuromuscular, hepatic or renal failure were included in this study. Anesthesia was induced and maintained with propofol, fentanyl, and N20. Normal core temperature was maintained by active warming of the upper part of the body. Blood electrolytes and the acid-base status were within the normal range. The accelerographic responses to Train-Of-Four supramaximal stimulation (TOF) of the ulnar nerve was monitored at the thumb. After obtaining a stable response with the accelerograph, the patients randomly received pancuronium (0.10 mg.kg-1, group I, n = 10 and group II, n = 10) or atracurium (0.50 mg.kg-1, group III, n = 10). An additional dose of atracurium (0.16 mg.kg-1, group I and III) or pancuronium (0.03 mg.kg-1, group II) was injected when the first response of TOF stimulation (T1) reached 25% of its initial value. Then the time to obtain a 25% twitch height of T1 (T25), the recovery index (RI 25-75), the delay to obtain 4 responses to TOF and an adequate recovery [TOF ratio of 0.70 (TOF70)] were monitored. Injection of 60% ED95 of atracurium after pancuronium resulted in a similar recovery of neuromuscular function as after 45% ED95 of pancuronium as shown by the same recovery of T25 (66.5 +/- 4.2 min versus 71.4 +/- 7.8 min, group I versus group II, p > 0.05) and TOF70 (131.6 +/- 15.7 min versus 144.0 +/- 17.5, group I versus II, p > 0.05). Nevertheless the RI 25-75 of group I was of intermediate duration between those of group II and III. Electrolytes and acid-base status were similar between groups at the beginning of surgery. Thus this study shows a synergistic effect of the combination of atracurium after pancuronium occurring in non hypothermic patients anesthetized without halogenated agents. Because the duration of action of the drug administered first governs the duration of action of the subsequent neuromuscular myorelaxant, the neuromuscular function should be closely monitored at the end of surgery if neuromuscular drugs are used in combination.