Prevention of etomidate-induced myoclonus: Which is superior: Fentanyl, midazolam, or a combination? A Retrospective comparative study

BACKGROUND In this retrospective comparative study, we aimed to compare the effectiveness of fentanyl, midazolam, and a combination of fentanyl and midazolam to prevent etomidate-induced myoclonus. MATERIAL AND METHODS This study was performed based on anesthesia records. Depending on the drugs that would be given before the induction of anesthesia with etomidate, the patients were separated into 4 groups: no pretreatment (Group NP), fentanyl 1 µg·kg-1 (Group F), midazolam 0.03 mg·kg-1 (Group M), and midazolam 0.015 mg·kg-1 + fentanyl 0.5 µg·kg-1 (Group FM). Patients who received the same anesthetic procedure were selected: 2 minutes after intravenous injections of the pretreatment drugs, anesthesia is induced with 0.3 mg·kg-1 etomidate injected intravenously over a period of 20-30 seconds. Myoclonic movements are evaluated, which were observed and graded according to clinical severity during the 2 minutes after etomidate injection. The severity of pain due to etomidate injection, mean arterial pressure, heart rate, and adverse effects were also evaluated. RESULTS Study results showed that myoclonus incidence was 85%, 40%, 70%, and 25% in Group NP, Group F, Group M, and Group FM, respectively, and were significantly lower in Group F and Group FM. CONCLUSIONS We conclude that pretreatment with fentanyl or combination of fentanyl and midazolam was effective in preventing etomidate-induced myoclonus.