Comparison of priming versus slow injection for reducing etomidate-induced myoclonus: a randomized controlled study.

Background: Etomidate injection is often associated with myoclonus. Etomidate injection technique influences the incidence of myoclonus. This study was designed to clarify which of the two injection techniques-slow injection or priming with etomidate-is more effective in reducing myoclonus.

Methods: This prospective randomized controlled study was conducted on 189 surgical patients allocated to three study groups. Control group (Group C, n = 63) received 0.3 mg/kg etomidate (induction dose) over 20 s. Priming group (Group P, n = 63) received pretreatment with 0.03 mg/kg etomidate, followed after 1 min by an etomidate induction dose over 20 s. Slow injection group (Group S, n = 63) received etomidate (2 mg/ml) induction dose over 2 min. The patients were observed for occurrence and severity of myoclonus for 3 min from the start of injection of the induction dose.

Results: The incidence of myoclonus in Group P (38/63 patients [60.3%], 95% CI [48-71.5%]) was significantly lower than in Group C (53/63 patients [84.1%], 95% CI [72.9-91.3%], P = 0.003) and Group S (49/63 patients [77.8%], 95% CI [66-86.4%], P = 0.034). Myoclonus of moderate or severe grade occurred in significantly more patients in Group C (68.3%) than in Group P (36.5%, P < 0.001) and Group S (50.8%, P = 0.046), but the difference between Groups P and S was not significant (P = 0.106).

Conclusions: Priming is more effective than slow injection in reducing the incidence of myoclonus, but their effects on the severity of myoclonus are comparable.