To the Editor:—

I read with interest the recent report of a study by Murphy et al. , 1in which they compared the effects of two muscle relaxants, the intermediate-duration drug rocuronium and the longer-duration drug pancuronium. Even using a nerve stimulator to titrate dosing, their patients were not able to be extubated for several hours after cardiac surgery (350 min for rocuronium vs.  500 min for pancuronium). I am concerned that some readers may draw the inference from these results that pancuronium is not indicated in cardiac surgery, as it is responsible for protracted postoperative intubation.

One certainly cannot find fault with a major conclusion of the paper, namely the tautology that the duration of a shorter-acting drug is shorter than the duration of a longer-acting drug. However, this report raises an additional question. How much of the authors’ results do they think are artifacts of experimental design? The patients in the study received muscle relaxants until approximately 30 min before the end of surgery. In their discussion, Murphy et al.  1describe the known sensitivity of cardiac surgical patients to nondepolarizing neuromuscular blocking drugs, and it is the routine clinical practice of many cardiac anesthesiologists to administer neuromuscular blockers at induction and prior to initiation of cardiopulmonary bypass only for most patients. The continued administration of these drugs according to the study's protocol may have resulted in a protracted duration not seen in clinical practice.

If these drugs are, indeed, responsible for prolonged postoperative intubation of 6–8 h, how do the authors account for the practice in some adult cardiac centers of extubating cardiac surgical patients very early, or the fact that children and adolescents can have their tracheas routinely and safely extubated in the operating room with pancuronium as the sole muscle relaxant? 2 

Murphy GS, Szokol JW, Marymont JH, Avram MJ, Vender JS, Rossengart TK: Impact of shorter-acting neuromuscular blocking agents on fast-track recovery of the cardiac surgical patient. A nesthesiology 2002; 96: 600–6
Kloth RL, Baum VC: Very early extubation in children after cardiac surgery. Crit Care Med 2002; 30: 787–91