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.

Keywords: Myoclonus - chemically induced, Etomidate, Anesthetics, Intravenous - adverse effects, Blood Pressure - drug effects, Drug Therapy, Combination - methods, Etomidate - adverse effects, Fentanyl - therapeutic use, Heart Rate - drug effects, Midazolam - therapeutic use, Myoclonus - prevention & control