Cumulation characteristics of cisatracurium and rocuronium during continuous infusion

Purpose: The dissimilar pharmacokinetic properties of cisatracurium (CIS) a nd rocuronium (ROC) predict different potential for drug cumulation when th ese drugs are administered by continuous infusion. A study was therefore un dertaken to compare cumulation potential of CIS and ROC during surgical pro cedures of relatively long duration (2-4 hr). Methods: Sufentanil/propofol-N2O anesthesia was administered to 40 ASA I an d II adults. In a double-blind protocol, patients were randomly allocated t o receive a continuous iv infusion of either CIS or ROC, titrated in progre ssive increments or decrements as required to achieve and maintain 95 +/- 5 % depression of the T I response of the adductor pollicis muscle, using a D atex NMT- 100 Relaxograph EMG monitor applied at the wrist. At the end of s urgery, 60 mu g.kg(-1) neostigmine plus 15 mu g kg atropine were administer ed for reversal. Results: The duration of infusion was 104 +/- 33 min in group CIS and 1 1 0 +/- 23 min in group ROC (P=NS). In both groups, a progressive decrease in potency-adjusted infusion rates was observed after 30 min, then stabilized beyond 60 min. When allowing for an initial period of stabilization, mean p otency-adjusted infusion requirements were: CIS 0.81 +/- 0.02 mu g.kg(-1) m in(-1) and ROC 5.58 +/- 1.94 mu g.kg(-1) min(-1). There were no differences between groups at any time with regard to potency-adjusted infusion requir ements necessary to maintain 90-99% block(P=NS), However, drug costs/hr for maintenance of neuromuscular block were less with CIS ($3.57 +/- 0.09) tha n with ROC ($6.03 +/- 0.27), P < 0.00 1. Conclusion: When adjusted to equipotency, infusion requirements of CIS and ROC vary at similar rates during general anesthesia. Despite pharmacokineti c differences, neither drug demonstrates cumulation for infusion lasting up to 3.5 hr.