title: The optimal effect-site concentration of remifentanil to attenuate the pain caused by propofol.
abstract: BACKGROUND
  The injection pain of propofol is a frequent and well-known adverse effect. This study was designed to determine the optimal effect-site concentration of remifentanil for minimizing injection pain during induction with propofol.
  
  
  METHODS
  A total intravenous anesthetic technique was used for patients undergoing general anesthesia and remifentanil was pretreated to reach a certain target concentration before propofol injection. Using Dixon's up-and-down method, the degree of pain described by the patient was used to adjust the target concentration of remifentanil for the next patient. Ten success-failure curves (crossovers) were sought to find the effect-site concentration (EC) of remifentanil for minimizing injection pain of propofol.
  
  
  RESULTS
  The EC of remifentanil in 50% and 95% of adult female population (EC(50) and EC(95)) for minimizing injection pain of propofol were 3.09 ng/ml (95% confidence limits [CI] 2.92-3.30 ng/ml) and 3.78 ng/ml (95% CI 3.45-3.95 ng/ml), respectively. Clinically significant hemodynamic compromise or respiratory complications were not found during remifentanil infusion.
  
  
  CONCLUSIONS
  Maintaining 3.78 ng/ml EC of remifentanil during induction with propofol attenuate propofol injection pain without serious adverse events in female patients undergoing general anesthesia and this method may provide the patient's comfort without preparing other drugs for pain relief.
authors.affiliation: Department of Anesthesiology and Pain Medicine, CHA Bundang Medical Center, CHA University, Seongnam, Korea.
authors.forename: Jong-Yeon
authors.initials: JY
authors.lastname: Lee
authors.forename: Hyeonjeong
authors.initials: H
authors.lastname: Yang
authors.forename: Seok Hwan
authors.initials: SH
authors.lastname: Choi
authors.forename: Dong Wook
authors.initials: DW
authors.lastname: Shin
authors.forename: Seung-Ki
authors.initials: SK
authors.lastname: Hong
authors.forename: Duk-Hee
authors.initials: DH
authors.lastname: Chun