Neuromuscular and Cardiovascular Effects of Mivacurium in Children

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Abstract
The neuromuscular and cardiovascular effects of mivacurium chloride (BW B1090U) were evaluated in 90 children (2-12 yr) during N2O:O2 halothane or N2O:O2 narcotic anesthesia. Neuromuscular response was evaluated by recording the force of contraction of the adductor of the thumb during train-of-four stimulation at 0.1 Hz. The children were divided into two groups. Patients in group A (n = 45) were anesthetized with N2O:O2 and halothane (1% inspired) and patients in group B (n = 45) were anesthetized with N2O:O2 and fentanyl or morphine. Each group was further divided into five subgroups of nine children. Children in the first three sets of subgroups (A1-A3, B1-B3) received an initial dose of 0.02, 0.04, 0.05, 0.06 or 0.07 mg/kg mivacurium to determine dose response relationships under the different anesthetic regimens. The ED50 and ED95 neuromuscular blocking doses calculated from this single dose technique were 0.051 mg/kg and 0.095 mg/kg, respectively, in children anesthetized with halothane N2O:O2, and 0.59 mg/kg and 0.11 mg/kg in children anesthetized with N2O:O2 narcotic. The fourth subset of each group (A4 and B4) received 0.09 mg/kg and 0.11 mg/kg mivacurium, the estimated ED95 for each respectively. The last subsets (A5 and B5) received 0.2 mg/kg. This dose induced 100% depression of the twitch response in all 18 patients in 1.8 .+-. 0.1 min, with recovery to 5%, 25%, and 95% of control occurring in 8.4 .+-. 0.5, 11.2 .+-. 0.6 and 18.4 .+-. 1.6 min, respectively. The recovery indices for all patients were 4.6 .+-. 0.6 min for 25-75% recovery and 9.7 .+-. 1.3 min for 5-95% recovery. In 17 patients the neuromuscular effects of mivacurium were satisfactorily antagonized by atropine 0.03 mg/kg and edrophonium 0.3 mg/kg. Furthermore, no clinically or statistically significant change in heart rate or blood pressure occurred following the administration of mivacurium. Mivacurium is a short-acting, nondepolarizing neuromuscular blocking agent that can be safely used in children.