Etomidate is known to trigger myoclonus during the induction of general anesthesia. This study aimed to evaluate whether pretreatment with a low dose of esketamine could reduce the occurrence of etomidate-induced myoclonus.One hundred adult patients scheduled for elective surgeries under general anesthesia were randomly assigned to two groups: the esketamine group (Group E) and the control group (Group C). Group E received 0.15 mg/kg of esketamine, while Group C received an equal volume of normal saline, administered two minutes before 0.3 mg/kg of etomidate. The primary outcome was the incidence of etomidate-induced myoclonus. Secondary outcomes included myoclonus severity, changes in haemodynamic parameters at different time points, and the occurrence of adverse effects such as dizziness, bradycardia, hypotension, and hallucinations from the time of pretreatment until etomidate injection.The incidence of myoclonus was significantly lower in Group E (20%) compared to Group C (62%). Pretreatment with esketamine also reduced moderate and severe myoclonus, though no significant difference was observed for mild myoclonus between the groups. Haemodynamic parameters, including mean arterial pressure and heart rate, did not differ significantly at any time point. The rates of dizziness, bradycardia, hypotension, and hallucination were comparable between groups.Administering 0.15 mg/kg of esketamine before etomidate induction significantly decreased the incidence and severity of myoclonus without affecting mild cases and maintained stable haemodynamic conditions.
