Pretreatment Of Ci-satracurium Reduces The Frequency And Severity Of Etomidate-induced Myoclonus

Objective To investigate the effect of pretreatment with a low dose of cis-atracurium on the occurrence of etomidate-induced myoclonus.Methods120ASA physical status I and II patients scheduled for elective surgery with general anesthesia. All patients were divided ramdomly and blindly into two groups with60cases each. A low dose of cis-atracurium (0.01mg/kg; Group A) or placebo (saline; Group C) was injected intravenously, which was followed by etomidate0.3mg/kg for anesthesia induction4minutes later within30seconds.1minute after the injection of etomidate, cis-atracurium0.14mg/kg and0.15mg/kg were given respectively. Both groups received fentanyl4ug/kg1minute later, tracheal intuhation was performed after muscle relaxant completely. Patients were monitored for myoclonic movements and pain on a scale of0-3. Patients were observed continuously by one anesthesiologist who was blinded as to group allocation, and who asked about injection site pain while infusing the etomidate Pain was graded as0(none),1(mild; reported only in response to questioning and without any behavioral signs),2(moderate; reported in response to questioning and accompanied by behavioral signs, or reported spontaneously without questioning), or3(severe; strong vocal response or response accompanied by facial grimacing, arm withdrawal, or tears). Patients were also observed continuously for occurrence of myoclonus, defined as an involuntary, short contraction of some muscle fibers, of a whole muscle, or of different muscles of one group, leading to a short observable movement of the corresponding body part. Intensity of myoclonus after injection of etomidate was graded as0(none),1(mild; movement at the finger or wrist only),2(moderate; involving the face and leg), or3(severe; generalized response or fast abduction of a limb). Bispectral index (BIS) was recorded continuously throughout the procedure. Noninvasive arterial blood pressure, and heart rate were recorded during the study period.Results The incidences of myoclonus was lower in group A(30.0%) than those in group SC(63.3%). In the latter group, there was no difference in the frequency of male (61.3%) and female (58.6%) patients experiencing myoclonus. The incidences of pain was no significant difference between two groups. BIS value was no significant defference between two groups. There was no significant difference in hemodynamics between two groups during anesthesia induction.Conclusion Preinjection with a small dose of cis-atracurium can effectively reduce etomidate-induced myoclonus during anesthesia induction.