AGE-RELATED VARIABILITY IN THE EFFECTS OF MIVACURIUM IN PEDIATRIC SURGICAL PATIENTS

Purpose: This study describes the effects of 0.3 mg.kg(-1) mivacurium in 180 paediatric patients between the ages of one month and 13 yr. Me thods: Alternate patients at each of two geographic sites received nit rous oxide-halothane or nitrous oxide-opioid anaesthesia. Neuromuscula r blockade was monitored by electromyography (Datex NMT), Blood pressu re and heart rate were recorded from an automated oscillometer, Trache al intubation was performed 90 sec after administration bimivacurium a nd conditions were judged by the Kneg scale. Results: There was no dif ference in the time course of block between anaesthetics or geographic sites. The average time to 90% block and 25% recovery was 10 min and 8.0 min at one month vs 2.3 min and 9.8 min at 12.5 yr of age. Intubat ion conditions were better during opioid (excellent in 92%) than durin g halothane anaesthesia (excellent in 78%) (P = 0.03), Diaphragmatic m ovement was less frequent in younger patients (P < 0.001). Intubation conditions did not differ between the two geographic sites. In the fir st minute after mivacurium, systolic and diastolic blood pressures dec reased (P < 0.001) to similar extents in all patients. A transient inc rease in the redness of the skin of the face, trunk, and/or arms was n oted during both anaesthetics (28% of infants, and 61% of children ove r five yr of age). Conclusion: The time course of block produced by mi vacurium is more rapid in younger paediatric patients, The lime course of mivacurium does not have the transatlantic variation which has bee n observed for vecuronium. Physiological changes suggestive of histami ne release were frequent. intubation conditions were very likely to be acceptable 90 sec after 0.3 mg.kg(-1) mivacurium.