The effect of remifentanil for reducing myoclonus during induction of anesthesia with etomidate.

BACKGROUND Myoclonic movement is a common problem during induction of anesthesia with etomidate. We investigated the influences of pretreatment with remifentanil on etomidate induced myoclonus. METHODS Ninety ASA class I patients were divided randomly into three groups. Group NS received normal saline 2 ml as placebo (n = 30), group R0.5 and group R1.0 were pretreated with remifentanil 0.5 microgram/kg (n = 30) or 1.0 microgram/kg (n = 30) 1 minute before induction with etomidate 0.3 mg/kg. Orotracheal intubation was performed after administration of rocuronium 0.5 mg/kg. We assessed the incidence, onset, duration and intensity of myoclonus. Mean arterial pressure (MAP), heart rate (HR) and bispectral index (BIS) were recorded during induction. RESULTS Twenty five patients developed myoclonus in group NS (83.3%), 3 patients in group R0.5 developed myoclonus (10%), as did 5 patients in group R1.0 (16.7%). Moderate to severe myoclonus of grade 3 and 4 were found 66.7% of patients in group NS, whereas no patients in both remifentanil pretreated groups developed this grade of myoclonus. The duration of myoclonus was reduced significantly in the remifentanil groups: 93.8 +/- 59.5 sec in group NS, 49.3 +/- 34.9 sec in group R0.5, 36.0 +/- 27.0 sec in group R1.0 (P < 0.05). HR was decreased by pretreatment with remifentanil prior to induction, while MAP and HR were decreased after induction with etomidate (P < 0.05). BIS changes were not different among the three groups. The dose dependent differences between the two remifentanil doses were not noticed. CONCLUSIONS Pretreatment with remifentanil significantly reduced the incidence, duration and intensity of etomidate induced myoclonus.