Remifentanil Pretreatment Prevents Myoclonus After Propofol Injection

Objective:To investigate the incidence of myoclonus induced by propofol infusion and the effect of remifentanil pretreatment on myoclonus after propofol infusion.Methods:64ASA physical status I-II, aged18to40years old, undergoing general anesthesia patients were randomly divided into two groups (n=32). Group C received4000mg/h propofol infusion until either the burst suppression ratio (BSR) on Bispectral index (BIS) monitor reached up to40%or the consumption of propofol greater than500mg. Then fentanyl and muscle relaxants were given for intubation. In group R the patients were first infused with remifentanil by target-controlled infusion. Target-controlled settings:plasma concentrations, Minto pharmacokinetic parameters, target concentration4ng/ml.10minutes after achievement of target concentration, propofol infusion was started using the same protocol of group C. During the trials, the occurrence of myoclonus and the severity of myoclonus were investigated by anesthesiologist, and the level of consciousness of each patient at time of myoclonus occurrence was also assessed. The effect-site propofol concentration was calculated by the pharmacokinetic model described by Marsh.Results:In group C, the myoclonus after propofol infusion was observed in24patients and the incidence of myoclonus reach was75%. No myoclonus was observed in group R. The BIS value at time of myoclonus occurrence was noted in the24patients and had a mean of29.8±5.3. The occurrence of myoclonus in22patients was prior to the occurrence of burst suppression and in2cases the myoclonic movements occurred after the burst suppression. The effect-site propofol concentration when the myoclonus occurred in24patients was5.28±1.75?g/ml, and was lower than the effect-site concentration of burst suppression (p<0.05).Conclusions:When the myoclonus was induced by propofol infusion, the patients were always in deep anesthetic state, and occurrence of myoclonus has shown to have no relation with the burst suppression of EEG; Remifentanil pretreatment at4ng/ml target concentration can effectively prevent myoclonus after propofol infusion.