title: The proper effect site concentration of remifentanil for prevention of myoclonus after etomidate injection.
abstract: 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.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Pusan National University School of Medicine, Yangsan, Korea.
authors.forename: Hyun Su
authors.initials: HS
authors.lastname: Ri
authors.forename: Sang Wook
authors.initials: SW
authors.lastname: Shin
authors.forename: Tae Kyun
authors.initials: TK
authors.lastname: Kim
authors.forename: Seung Wan
authors.initials: SW
authors.lastname: Baik
authors.forename: Ji Uk
authors.initials: JU
authors.lastname: Yoon
authors.forename: Gyeong Jo
authors.initials: GJ
authors.lastname: Byeon