Background. In children, the incidence of injection pain at i.v. anaesthetic induction with Etomidate-Lipuro is low when compared with propofol mixed with lidocaine (5%). However, the incidence of involuntary myoclonic movements (MM) after induction of anaesthesia is higher compared with propofol (85% vs 15%). In adults, the incidence of MM is reported to be significantly reduced if a small priming dose is administered immediately before the main injection of etomidate. The aim of this prospective, randomized, double-blind, placebo-controlled clinical trial was to investigate if a small priming dose of etomidate effectively can reduce the incidence of MM also in children. Methods. Eighty ASA I-II children (1-15 yr) were randomized to receive either a small priming dose of etomidate (0.03 mg kg(-1)) or a lipidemulsion placebo. A standardized induction dose of etomidate (0.3 mg kg(-1)) was administered 60 s after the priming dose. The occurrence and severity (observational score 0-3) of MM was defined as the primary endpoint of the study and was recorded during a 2 min period after induction of anaesthesia. A post hoc analysis was performed regarding the incidence of MM with respect to age. Results. No difference in the occurrence or severity of MM was found between the two study groups, the total incidence of MM being 73.8% (95% confidence interval: 62.7-83.0%). The incidence of MM (score >0) was found to be statistically higher in the age group 5-10 yr compared with <5 yr; and >10 yr (P=0.0008 and 0.01730, respectively). The MM scores were highest in patients aged 5-10 yr (P=0.0021). Conclusions. Children in the age range of 5-10 yr appear to be especially prone to react with involuntary MM after i.v. induction of anaesthesia with etomidate. The use of a small, non-sedative, priming dose did not influence the incidence of involuntary MM after i.v. induction of anaesthesia with etomidate in children 1-15 yr of age.
