CONTINUOUS INFUSION OF MIVACURIUM IN CHILDREN

Mivacurium is a new short-acting competitive neuromuscular blockingagent. Infusion requirements for the maintenance of a stable90–99% muscle twitch depression were determined in 28children anaesthetized with nitrous oxide and 1% halothane (inspired)in oxygen or nitrous oxide in oxygen and opioid. Neuromuscularblock was assessed by monitoring the force of contraction ofthe adductor of the thumb during train-of-four (TOF) stimulationat 0.1 Hz. Infusion rate and twitch depression were analysedfrom 15 to 75 min and from 75 to 135 min after the start ofthe infusion. In the first period of evaluation, the mean infusionrequirement was 10.4 (SEM 0.92) µg kg^–1 min^–1during the halothane anaesthesia and 13 (1.4) µg kg^–1min^–1 during the opioid anaesthesia (P < 0.05). Thisdifference was present also during the second 60-min period.There was no significant correlation between infusion ratesrequired to maintain > 90% depression of the first twitch(T1) of the TOF and plasma cholinesterase concentrations. Regardlessof the anaesthetic regimen, children recovered rapidly afterdiscontinuing the infusion. The recovery index (25–75% recovery of T1) for all patients was 5.4 (0.57) min with nosignificant differences between the groups.     

NEUROMUSCULAR AND CARDIOVASCULAR EFFECTS OF DOXACURIUM IN CHILDERN ANAESTHETIZED WITH HALOTHANE

The neuromuscular and cardiovascular effects of doxacurium chloride(BW A938U) were evaluated in 27 children (2–12 yr) anaesthetizedwith 1% halothane and nitrous oxide in oxygen. In nine childrenthe incremental technique was used to establish a cumulativedose-response curve by train-of-four stimulation. The remainingchildren received either 30 or 50 µg kg^–1 of thedrug as a single bolus. The median ED₅₀ and ED ₉₅ of doxacuriumin children were 19 and 32 µg kg^–1, respectively.No clinically significant change in heart rate or arterial pressureoccurred. Following doxacurium 30 µg kg^–1 and 50µg kg^–1, recovery to 25% of control occurred in25 (SEM 6) and 44 (3) min, respectively. The recovery index(25–75% of control) was 27 (2) min. The duration of actionof doxacurium is similar to that of tubocurarine and dimethyl-tubocurarinein children. Compared with adults, children seem to requiremore doxacurium (µg kg^–1) to achieve a comparabledegree of neuromuscular depression, and they recover more rapidly. Presented in part at the American Society of AnesthesiologistsAnnual Meeting, October 1987, and the International AnesthesiaResearch Society Meeting, March 1988.