Reducing myoclonus after etomidate

Background: The authors hypothesized that myoclonus after etomidate is dose -related, could be suppressed when small doses of etomidate were administer ed before induction, and is unassociated with seizure-like activity on elec troencephalogram (EEG). Methods: Three studies were performed. In the first study, 36 men were rand omly 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 allocate d 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 subje cts in the first two studies. In a third study, 60 patients were randomly a llocated 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 afte r 0.300 mg/kg, Incidence of myoclonus was dose-related (P less than or equa l to 0.01), In Study 2, two volunteers (25%) with etomidate pretreatment ha d mild myoclonus compared to six (75%) with placebo pretreatment (P less th an or equal to 0.05). EEG changes, other than delta waves, were not seen du ring myoclonic epochs. In Study 3, myoclonus was less likely after the smal l pretreatment doses (0.030 or 0.050 mg/kg) than after the large dose (0.07 5 mg/kg, P 0.01). Conclusions: Incidence and intensity of myoclonus after induction with etom idate are dose-related, suppressed by pretreatment, and unassociated with s eizure-like EEG activity.