SYNERGISM BETWEEN MIVACURIUM AND PANCURONIUM IN ADULTS

Mivacurium could be a useful agent as a final dose of a muscle relaxan t following pancuronium if only additivity exists between these agents . We examined the interaction between mivacurium and pancuronium in 70 patients (ASA I-II) during propofol-alfentanil-N2O-O-2 anaesthesia. N euromuscular function was monitored by adductor pollicis EMG. Firstly we established dose-response curves for mivacurium and pancuronium. Th ereafter; 20 patients received a combination of 0.5 times the ED(50) d oses of mivacurium and pancuronium (cMP) determined in the first part of this study. Patients were randomized to receive the cMP to the same IV-line (n=10) or to two separate IV-iines in opposite hands (n=10). ED(50) values for mivacurium and pancuronium were 57.7 and 37.1 mu g k g(-1), respectively, Maximal neuromuscular block following the cMP was 91.81+/-5.0% (mean+/-SD). This was highly significantly different fro m the estimated 50% NMB if only additivity exists between mivacurium a nd pancuronium (P=0.0001). After the cMP, the 25-75% recovery lime was 9.4+/-1.3 min and the dme to train-of-four ratio of 0.70 was 35.8+/-5 .4 min. There was no statistical difference in any recorded neuromuscu lar parameter between the two subgroups receiving mivacurium and pancu ronium to the same or to opposite hands (P>0.40). We conclude that a s ignificant synergism exists between mivacurium and pancuronium which m ay indicate that mivacurium does not produce a short-acting NMB if giv en after pancuronium. We do not recommend using mivacurium together wi th pancuronium.