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.
Keywords: Etomidate; Myoclonus; Pretreatment; Remifentanil.