[Mivacurium--a new muscle relaxant compared with atracurium and vecuronium].

This study investigates the effects of mivacurium (3 times ED95) on neuromuscular block, intubation conditions and general safety in comparison with equipotent doses of atracurium and vecuronium. Following Ethical Care Committee approval and informed consent, 90 ASA I+II patients aged 18 to 65 were studied undergoing elective ENT surgery. Anaesthesia was induced with 1.5 mg/kg propofol and 0.2 mg/kg alfentanil and maintained through continuous infusion of propofol (8 to 10 mg . kg-1 . h-1) and nitrous oxide in oxygen. After achieving stable anaesthesia, the patients received bolus injections of mivacurium (0.20 mg/kg, n = 30), atracurium (0.69 mg/kg, n = 30) or vecuronium (0.14 mg/kg, n = 30) for endotracheal intubation. Intubation was attempted 120 s after drug application and the intubation conditions were assessed. Relaxation was recorded using peripheral nerve stimulation (Train of four). During the observation period, signs of histamine release, respiratory difficulty, cardiovascular events or other adverse signs were monitored. Onset of relaxation was longer for mivacurium (2.3 +/- 1.3 min) compared with atracurium (1.4 +/- 0.7 min) or vecuronium (1.3 +/- 0.3 min). Intubation conditions 120 s after drug application were good or very good in only 67% of cases given mivacurium compared with 90% given atracurium and 100% given vecuronium. The recovery time (DUR 25) was shorter in the mivacurium group (19.5 +/- 7.9 min) compared with atracurium (54.7 +/- 6.6 min) and vecuronium (44.3 +/- 8.6 min). Heart rate and blood pressure were similar in all groups. Facial flushing and mild bronchospasms as signs of histamine release resulted more often in the mivacurium (20%) and atracurium groups (23%) than in the vecuronium group (3%). In contrast to atracurium and vecuronium, recovery from mivacurium-induced neuromuscular blockade is rapid. However, the onset time after 3 times ED95 was significantly longer for mivacurium than for atracurium or vecuronium.