Effect of Pretreatment with a Small Dose of Esketamine on Myoclonus Induced by Etomidate: A Randomized Controlled Trial.

Background: Etomidate has been observed to precipitate myoclonus in patients undergoing induction of general anaesthesia. This study was designed to investigate the effect of pretreatment with a small dose of esketamine on the incidence of myoclonus induced by etomidate.

Methods: One hundred adult patients, who were scheduled to undergo selective operations with general anesthesia, were randomly divided into two groups, with one group receiving esketamine (Group E) and the other receiving normal saline (Group C). The group receiving esketamine (Group E) was administered an injection of 0.15 mg/kg of esketamine, while the control group (Group C) was given an equivalent volume of normal saline two minutes before the administration of 0.3 mg/kg of etomidate. The primary objective was to determine the incidence of etomidate-induced myoclonus. Secondary endpoints included the severity of etomidate-induced myoclonus and changes in haemodynamic variables at various time intervals. Additionally, the incidence of adverse effects such as dizziness, bradycardia, hypotension and hallucination were recorded from the administration of esketamine or normal saline to the injection of etomidate.

Results: The incidence of myoclonus was significantly lower in Group E (20%) than in Group C (62%). Compared with the control group, the esketamine group also experienced a reduction in the moderate and severe of myoclonus. However, there was no statistically significant difference between the two groups for mild etomidate-induced myoclonus. The haemodynamic data (mean arterial pressure and heart rate) showed no statistically significant differences between two groups at the three time points. The incidence of dizziness, bradycardia, hypotension and hallucination was similar in both groups.

Conclusion: Pretreatment with 0.15 mg/kg esketamine prior to anaesthesia induction with etomidate was observed to markedly reduce the incidence and severity of myoclonus, while having no effect on mild etomidate-induced myoclonus and maintaining a stable haemodynamic status.