title: Butorphanol pre-treatment prevents myoclonus induced by etomidate: a randomised, double-blind, controlled clinical trial.
abstract: OBJECTIVE
  Myoclonic movements are common problems during induction of anaesthesia with etomidate. The myoclonus occurring after etomidate administration may represent a form of seizure. Agonistic modulation of the κ opiate receptor may reduce seizures, and butorphanol acts in such a manner. The aim of this randomised, double-blind, placebo-controlled clinical trial was to test our hypothesis that pre-treatment with butorphanol might reduce the incidence and severity of myoclonus induced by etomidate.
  
  
  METHODS
  Patients (108) with American Society of Anaesthesiologists physical status I or II were randomly assigned to one of two groups to receive either 0.015 mg/kg of butorphanol (n = 54) or saline (n = 54) intravenously. At two minutes after infusion of butorphanol or saline, 0.3 mg/kg etomidate was given. The occurrence and severity (observational score of 0-3) of myoclonus was assessed during 2 minutes after administration of etomidate. For each patient, blood pressure (BP), saturation of peripheral oxygen (SpO₂), and heart rate (HR) were measured.
  
  
  RESULTS
  The incidence of myoclonus was significantly lower in Group Butorphanol than in Group Saline (13.0% vs 79.6%; RR = 0.163, 95%CI: 0.081-0.329; χ² = 48.265, p <0.0001). The severity levels of myoclonic movement were also significantly lower in Group Butorphanol than in Group Saline (p <0.0001). Throughout the procedure, changes of BP, SpO₂, and HR did not differ between the groups. There were no problems with bradycardia or hypotension.
  
  
  CONCLUSIONS
  Infusion of 0.015 mg/kg butorphanol 2 minutes before etomidate administration is effective for suppressing myoclonus induced by etomidate during induction of general anaesthesia.
authors.affiliation: Department of Anaesthesiology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Liang
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Anaesthesiology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Ding
authors.affiliation: Department of Anaesthesiology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Huiyu
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Anaesthesiology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.
authors.forename: Yanning
authors.initials: Y
authors.lastname: Qian
authors.affiliation: Key Laboratory of Modern Toxicology (Ministry of Education), School of Public Health, Nanjing Medical University, Nanjing, China.
authors.forename: Zhong
authors.initials: Z
authors.lastname: Li
mesh_terms: D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D018686:Anesthetics, Intravenous / Q000009:adverse effects*; D002077:Butorphanol / Q000008:administration & dosage*; D004311:Double-Blind Method; D005045:Etomidate / Q000009:adverse effects*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009207:Myoclonus / Q000139:chemically induced* / Q000517:prevention & control*
chemical_list: D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D002077:Butorphanol; D005045:Etomidate