To the Editor:-Kopman et al. [1] have performed a very valuable service in examining the incidence of residual neuromuscular paralysis after the use of mivacurium and pancuronium. It is time that the many reports describing the high incidence of residual block after the use of pancuronium were put to scrutiny by a carefully performed clinical investigation. They demonstrated what can be achieved by a select group of careful and experienced clinicians interested in muscle relaxants when neuromuscular block is controlled using train-of-four (TOF) monitoring and when reversal is attempted with sufficient doses of anticholinesterases given at the appropriate time. The questions are 1) Can their results be achieved by everyone? 2) Are they good enough? 3) Will they save money?

The principal finding of the study was that, on arrival in postanesthesia care unit (PACU), the incidence of residual neuromuscular paralysis was low. TOF ratios averaged 0.93 after mivacurium and 0.85 after pancuronium; 54 of 56 patients given pancuronium had TOF ratios of greater or equal to 0.7. At first glance, this level of neuromuscular recovery after long-acting relaxants is much greater than previously reported by several investigators since Viby-Mogensen et al. [2] in 1979. Our own studies in Montreal showed that 17 of 47 adults given pancuronium had TOF < 0.7 when tested in PACU compared with only 2 of 46 given atracurium and 5 of 57 given vecuronium. [3] The difference, however, may be the time between reversal of block and neuromuscular testing in PACU. Kopman et al. tested patients given pancuronium at 30 min and those given mivacurium at 19.7 min after reversal. In our studies in Montreal, adults were tested 13–15 min after reversal, and children were tested 15–18 min after reversal. [4] A more recent study in Vancouver, examining residual block after mivacurium, tested adults at 12–14 min and children at 8–9 min. [5] Kopman et al. showed that 10 min after reversal, the mean TOF ratio in patients given pancuronium was 0.65. The results are very similar. It is likely that by administering muscle relaxants and their antagonists carefully, other clinicians will be able to achieve results similar to Kopman et al. Whether the patients demonstrate residual block on arrival in PACU depends on how long it takes to get there!

It is ironic that in the same issue of Anesthesiology, Dexter and Macario calculated that the cost of running an operating room (OR) at Stanford University Medical Center was 8.13 dollars per min. [6] Simplistic arithmetic suggests that in New York, the average OR cost for patients given pancuronium was 83 dollars more than for those given mivacurium. Muscle relaxants are cheap; OR time is expensive.

David R. Bevan, M.B., F.R.C.A.; Joan C. Bevan, M.D., F.R.C.A.

Department of Anaesthesia; University of British Columbia; Vancouver General Hospital

855 West 12th Avenue; Vancouver, British Columbia V5Z 4E3; Canada

(Accepted for publication April 5, 1997.)

Kopman AF, Ng J, Zank LM, Neuman GG, Yee PS: Residual postoperative paralysis. Pancuronium versus mivacurium, does it matter? Anesthesiology 1996; 85:1253-9.
Viby-Mogensen J, Jorgensen BC, Ording H: Residual curarization in the recovery room. Anesthesiology 1979; 50:539-41.
Bevan DR, Smith CE, Donati F: Postoperative neuromuscular blockade: A comparison between atracurium, vecuronium, and pancuronium. Anesthesiology 1988; 69:272-6.
Baxter RMN, Bevan JC, Samuel J, Donati F, Bevan DR: Postoperative neuromuscular function in pediatric day-care patients. Anesth Analg 1991; 72:504-8.
Bevan DR, Kahwaji R, Ansermino JM, Reimer E, Smith MF, O'Connor GAR, Bevan JC: Residual block after mivacurium with or without edrophonium reversal in adults and children. Anesthesiology 1996; 84:362-7.
Dexter F, Macario A: Applications of information systems to operating room scheduling (editorial). Anesthesiology 1996; 85:1232-4.