• Liang He, Ying Ding, Huiyu Chen, Yanning Qian, and Zhong Li.
• Department of Anaesthesiology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, China.
• Swiss Med Wkly. 2014 Jan 1;144:w14042.

Questions Under StudyMyoclonic 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.MethodsPatients (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.ResultsThe 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.ConclusionsInfusion of 0.015 mg/kg butorphanol 2 minutes before etomidate administration is effective for suppressing myoclonus induced by etomidate during induction of general anaesthesia.

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