MIVACURIUM IN INFANTS AND CHILDREN

Mivacurium is the only available short-acting nondepolarizing muscle r elaxant in clinical use. It is a bis-quaternary benzylisoquinolinium e ster hydrolysed by plasma-cholinesterase into inactive compounds. The ED50 and ED95 in children are about 50 mu g.kg(-1) and 90 mu g.kg(-1) respectively. In infants, they have a tendency to be lower. A standard intubating dose of 0.25 mg.kg(-1) causes complete neuromuscular depre ssion in 1.5-2 min, recovery to 5% in 6-10 min, and complete recovery in 15-20 min. The recent tendency is to use 0.3 mg.kg(-1) to obtain be tter intubating conditions with slight prolongation of effect, Since t he recovery profile of mivacurium is independent of the dose and durat ion, it is most suitable for administration by continuous infusion. Th e infusion requirement in children is 10-16 mu g.kg(-1) min(-1), which is about twice that of adults. Cutaneous flushes from histamine relea se are commonly seen with the larger doses of mivacurium; however, the associated hypotensive effects are minimal and counteracted by the tr acheal intubation. The duration of action of mivacurium is prolonged i n patients with cholinesterase deficiency. Mivacurium's neuromuscular effects can be satisfactorily antagonized by edrophonium or neostigmin e.