Neuromuscular blocking drugs in infants and children.

Neuromuscular blocking drugs are valuable adjuncts to the practice of pediatrics. Monitoring of drug effects is technically more difficult in the younger patient. Nevertheless, careful observation of drug effects will improve the usefulness of NMB and safeguard the patient from prolonged weakness. Although there are differences in neuromuscular function with age in the pediatric age range, the differences between the NMB currently available are greater than the differences between the patients. Thus, the only uniform finding across age and all drugs is that onset of drug effect is more rapid in the infant than in the child when circulatory function is normal. In general, children require more of all NMB on a mg/kg basis than do infants or adults to obtain the same effect. Children recover from NMB more rapidly than do patients of other ages. Infants, however, may recover more rapidly than do any other patients from the effects of drugs such as mivacurium which are metabolized in the plasma. Tables 4 and 5 summarize doses, onset of action, and duration of NMB. Please note in Table 4 that succinylcholine is only used for endotracheal intubation, whereas the other nondepolarizing muscle relaxants can be used for endotracheal intubation or to maintain some degree of muscle paralysis in the child whose trachea is already intubated. Nondepolarizing muscle relaxants (e.g., mivacurium, ORG 9426, atracurium, vecuronium) are used both for initial bolus for endotracheal intubation and maintenance of muscle relaxation. Long-acting drugs (e.g., pancuronium, pipecuronium, and doxacurium), however, are used more commonly in small incremental doses to maintain muscle paralysis in patients already intubated. The advantages of these long-acting drugs are minimal cardiovascular side effects (i.e., tachycardia or hypotension from histamine release) and longer dosing interval. In all children, the dosing interval should be adjusted to the needs of the individual. In children with renal insufficiency or in those receiving drugs which impair neuromuscular function (e.g., aminoglycosides), the interval at which supplemental doses are required is longer than normal.