DOSE-RESPONSE AND MINIMUM-TIME TO SATISFACTORY INTUBATION CONDITIONS AFTER MIVACURIUM IN CHILDREN

We assessed neuromuscular blocking effects and tracheal intubation con ditions following mivacurium in 121 anaesthetised children aged 1-10 y ears. The study was conducted in three parts. Parts 1 and 2 were under taken during thiopentone-alfentanil-nitrous oxide anaesthesia; neuromu scular blockade was evaluated by recording the force of contraction of the adductor pollicis in response to train-of-four stimulation at 0.1 Hz. In part 1 the potency of mivacurium was determined in 15 children using a single dose-response technique; in part 2 onset and recovery times were determined in six children following a dose of mivacurium 0 .2 mg.kg(-1). In part 3 of the study, clinical intubation conditions w ere assessed in two groups of 50 children whose tracheas were intubate d 60 or 90 s after injection of mivacurium 0.2 mg.kg(-1) during thiope ntone-nitrous oxide anaesthesia. The ED(50) and ED(95) of mivacurium w ere 54 and 105 mu g.kg(-1) respectively. The times to 90% and 100% dep ression of control twitch were 1.3 (0.3) and 1.9 (0.5) min; times to 5 %, 25%, 75% adn 90% recovery were 6.4 (1.0), 8.4(1.1), 12.5(1.1) and 1 4.4(1.9) min, respectively. Intubation conditions were rated satisfact ory in 33/50 children (0.66, 95% confidence interval 0.51-0.79) at 60 s and in 49/50 children (0.98, 95% confidence interval 0.89-1.0) at 90 s (p = 0.0001). Intubation conditions 90 s after mivacurium 0.2 mg.kg (-1) were significantly better than those obtained in 10 patients give n anaesthetic drugs alone (p = 0.002).