Reducing myoclonus after etomidate

Background: The authors hypothesized that myoclonus after etomidate is dose-related, could be suppressed when small doses of etomidate were administered before induction, and is unassociated with seizure-like activity on electroencephalogram (EEG). Methods: Three studies were performed. In the first study, 36 men were randomly assigned to receive 0.025, 0.050, 0.075, 0.100, 0.200, or 0.300 mg/kg of etomidate, In a second crossover study, eight men were randomly allocated to receive either a pretreatment dose of 0.050 mg/kg etomidate or placebo 50 s before 0.300 mg/kg etomidate was injected. EEG was recorded for subjects in the first two studies. In a third study, 60 patients were randomly allocated to one of three pretreatment doses of etomidate: 0.030, 0.050, or 0.075 mg/kg before 0.300 mg/kg was given. Results: In Study 1, myoclonus was not observed after 0.025 or 0.050 mg/kg etomidate, One volunteer had myoclonus after 0.075 mg/kg and another after 0.100 mg/kg etomidate; three had myoclonus after 0.200 mg/kg; and five after 0.300 mg/kg, Incidence of myoclonus was dose-related (P less than or equal to 0.01), In Study 2, two volunteers (25%) with etomidate pretreatment had mild myoclonus compared to six (75%) with placebo pretreatment (P less than or equal to 0.05). EEG changes, other than delta waves, were not seen during myoclonic epochs. In Study 3, myoclonus was less likely after the small pretreatment doses (0.030 or 0.050 mg/kg) than after the large dose (0.075 mg/kg, P 0.01). Conclusions: Incidence and intensity of myoclonus after induction with etomidate are dose-related, suppressed by pretreatment, and unassociated with seizure-like EEG activity.