Comparison of butorphanol or midazolam alone and combination of the two drugs in preventing etomidate-induced myoclonus during anesthesia induction

Objective To compare butorphanol or midazolam alone and combination of the two drugs in preventing etomidate-induced myoclonus during anesthesia induction. Methods One hundred sixty patients, aged 40–64 yr, with body mass index of 20–25 kg/m2, of American Society of Anesthesiologists physical statusⅠ or Ⅱ, scheduled for elective operations under general anesthesia, were randomly allocated into 4 groups with 40 patients in each group: control group(group C), butorphanol group(group B), midazolam group(group M), and butorphanol combined with midazolam group(group BM). Before induction of anesthesia, butorphanol 15.0 μg/kg, midazolam 50 μg/kg, and butorphanol 7.5 μg/kg combined with midazolam 25 μg/kg were injected intravenously over 30 s in B, M and BM groups, respectively.The equal volume of normal saline was given in group C. And 2 min later, etomidate 0.3 mg/kg was injected intravenously over 1 min.The occurrence of myoclonus was recorded within 2 min after administration of etomidate, and the severity of myoclonus was assessed. Results Compared with group C, the incidence and severity of myoclonus were significantly decreased in B, M and BM groups(P 0.05). Conclusion Butorphanol or midazolam alone produces similar efficacy in preventing etomidate-induced myoclonus during anesthesia induction, and the combination of the two drugs provides better efficacy than either alone in the patients. Key words: Butorphanol; Midazolam; Etomidate; Myoclonus