Clinical Research Article Korean J Anesthesiol 2011 August 61(2): 127-132 http://dx.doi.org/10.4097/kjae.2011.61.2.127 The proper effect site concentration of remifentanil for prevention of myoclonus after etomidate injection Hyun Su Ri, Sang Wook Shin, Tae Kyun Kim, Seung Wan Baik, Ji Uk Yoon, and Gyeong Jo Byeon Department of Anesthesiology and Pain Medicine, Pusan National University School of Medicine, Yangsan, Korea Background: Etomidate frequently induces myoclonus when administered intravenously with bolus injection during anesthetic induction. This can be bothersome for the anesthesiologist. The dose of remifentanil appropriate for preventing myoclonus without side effects was investigated. Methods: All patients with American Society of Anesthesiologists (ASA) physical status I-III were divided into three groups (n = 33 per group) according to the pretreatment effect site concentration of remifentanil (Ultiva, Glaxo- Wellcome, München, Germany) of 0, 2 or 4 ng/ml (Group N: 0 ng/ml, Group R: 2 ng/ml, Group Q: 4 ng/ml) by a target controlled infusion (TCI) system. After a 0.3 mg/kg dose of etomidate was injected intravenously for over 1 minute for anesthetic induction, myoclonus was observed. Before the etomidate injection, the patients were pretreated with remifentanil and their side effects were monitored. Results: The number of patients showing myoclonus was significantly different among the groups. The incidence of myoclonus was 81%, 12% and 0% (groups N, R, and Q, respectively, P < 0.01). Side effects including bradycardia and hypotension did not occur in either Group R or Q. Chest wall rigidity occured in 45% of patients in Group Q. Conclusions: Administration with a 2 ng/ml effect site concentration of remifentanil could reduce the incidence of myoclonus caused by etomidate bolus injection without chest wall rigidity. (Korean J Anesthesiol 2011; 61: 127-132) Key Words: Etomidate, Myoclonus, Remifentanil. Received: April 30, 2010. Revised: 1st, May 24, 2010; 2nd, July 17, 2010. Accepted: January 6, 2011. Corresponding author: Sang Wook Shin, M.D., Department of Anesthesiology and Pain Medicine, Pusan National University Yangsan Hospital, Beomeo-ri, Mulgeum-eup, Yangsan 626-770, Korea. Tel: 82-55-360-2129, Fax: 82-55-360-2149, E-mail: shinsw@pusan.ac.kr This is a theisis for a master's degree. CC This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http:// creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright ⓒ the Korean Society of Anesthesiologists, 2011 www.ekja.org