THE DURATION OF ACTION OF MIVACURIUM IS PROLONGED IF PRECEDED BY ATRACURIUM OR VECURONIUM

We studied 45 patients (ASA I-II) during propofol-alfentanil-N2O-O-2 a naesthesia to determine if recovery from neuromuscular block induced b y mivacurium is influenced differently by prior injection of atracuriu m or vecuronium. Neuromuscular function was monitored by adductor poll icis EMG. Patients were randomized to receive two doses of either miva curium (150 and 70 mu g kg(-1)), atracurium (350 and 75 mu g kg(-1)) o r vecuronium (70 and 15 mu g kg(-1)) followed by a final dose of mivac urium 70 mu g kg(-1). The second and third doses of the muscle relaxan ts were administered at 25-30% recovery of the E(1) (first EMG respons e in the train-of-four series). Following the final dose of mivacurium , the EMG response recovered to 25 and 95% in 10.4+/-3.9 and 19.7+/-5. 7 min (mean+/-SD), respectively if mivacurium was the only muscle rela xant. Respective times were 100% longer if mivacurium had been precede d by atracurium (23.8+/-3.3 and 39.8+/-6.9 min) or vecuronium (22.6+/- 3.5 and 41.1+/-7.9 min) (P=0.0001). The 25-75% recovery times in the t hree groups were 4.9+/-1.0, 8.7+/-2.4 and 10.5+/-2.5 min, respectively (P=0.0001). Our results indicate that there is no benefit in giving m ivacurium at the end of surgery after peroperative use of atracurium o r vecuronium.