The efficacy and safety of mivacurium in pediatric patients.

Background: Mivacurium is the shortest acting nondepolarizing muscle relaxant currently available; however, the effect of different dosages and injection times of intravenous mivacurium administration in children of different ages has rarely been reported. This study was aimed to evaluate the muscle relaxant effects and safety of different mivacurium dosages administered over different injection times in pediatric patients.

Methods: Six hundred forty cases of pediatric patients, aged 2 m-14 years, ASA I or II, were divided into four groups (Groups A, B, C, D) according to the age class (2-12 m, 13-35 m, 3-6 years and 7-14 years) respectively, also each group were divided into four subgroups by induction dose (0.15, 0.2 mg/kg in 2-12 m age class; 0.2, 0.25 mg/kg in other three age classes), and mivacurium injection time (20 s, 40 s), totally 16 subgroups. Neuromuscular transmission was monitored with supramaximal train-of-four stimulation of the ulnar nerve. Radial artery blood (1 ml) was sampled to quantify plasma histamine concentrations before and 1, 4, and 7 min after mivacurium injection (P0, P1, P2 and P3).

Results: Five hundred sixty-two cases completed the study. There were no demographic differences within the four groups. The onset time of 0.2 mg/kg groups in 2-12 m aged patients were shorter than those of 0.15 mg/kg groups (189 ± 64 s vs. 220 ± 73 s, 181 ± 60 s vs. 213 ± 71 s, P <0.05), and the recovery times were no statistical differences. The T1 25% recovery time of 0.2 mg/kg in 3-6 years aged patients was shorter than that of 0.25 mg/kg group (693 ± 188 s vs. 800 ± 206 s, P <0.05). The onset and recovery times of mivacurium were not different in 13-35 m and 7-14 years aged patients. The plasma concentrations of histamine at P0, P1, P2 and P3 were not different within four groups.

Conclusions: The induction dose and injection time of mivacurium had mostly insignificant effects on onset and recovery times. The main exception to this was that in 2-12 m aged patients, increasing the dose of mivacurium from 0.15 to 0.2 mg/kg accelerated the onset time by about 30 s. Mivacurium produced no significant release of histamine in any age group at the doses studied.

Trial Registration: ClinicalTrials.gov Identifier- NCT02117401 , July 14, 2014. (Retrospectively registered).