title: Optimal effect-site concentration of remifentanil when combined with dexmedetomidine in patients undergoing cystoscopy.
abstract: BACKGROUND
  Cystoscopic procedure is a very common practice in the field of urology due to its ability to survey the bladder for a variety of indications. However, patients who undergo cystoscopy feel intense pain and discomfort. This study investigated the half maximal effective concentration (EC50) of remifentanil in preventing cystoscope insertion pain under sedation using dexmedetomidine.
  
  
  METHODS
  The study was prospectively conducted on 18 male patients, aged 18 to 65. Remifentail infusion was initiated together with dexmedetomidine, and started at a dose of 2.4 ng/ml on the first patient. The effect-site concentration (Ce) of remifentanil for each subsequent patient was determined by the previous patient's response using Dixon's up-and-down method with an interval of 0.3 ng/ml. Patients received a loading dose of 1.0 µg/kg dexmedetomidine over 10 minutes, followed by a maintenance dose of 0.6 µg/kg/hr. After the patient's OAA/S score (Observer's Assessment of Alertness/Sedation scale) reached 3-4, and the Ce of remifentanil reached target concentration, the urologist was allowed to insert the cystoscope and the pain responses were observed.
  
  
  RESULTS
  The effect-site concentration of remifentanil required to prevent cystoscope insertion pain in 50% of patients under sedation using dexmedetomidine was 1.30 ± 0.12 ng/ml by Dixon's up-and-down method. The logistic regression curve of the probability of response showed that the EC50 and EC95 values (95% confidence limits) of remifentanil were 1.33 ng/ml (1.12-1.52 ng/ml) and 1.58 ng/ml (1.44-2.48 ng/ml), respectively.
  
  
  CONCLUSIONS
  Cystoscopic procedure can be carried out successfully without any pain or adverse effects by optimal remifentanil effect-site concentration (EC50, 1.33 ng/ml; EC95, 1.58 ng/ ml) combined with sedation using dexmedetomidine.
authors.affiliation: Department of Anesthesioloy and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.
authors.forename: Bongha
authors.initials: B
authors.lastname: Heo
authors.affiliation: Department of Anesthesioloy and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.
authors.forename: Minsun
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Anesthesioloy and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Anesthesioloy and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.
authors.forename: Sanghee
authors.initials: S
authors.lastname: Park
authors.affiliation: Department of Anesthesioloy and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea.
authors.forename: Seongwook
authors.initials: S
authors.lastname: Jeong
keywords: Cystoscopy; Dexmedetomidine; Monitored anesthesia care; Remifentanil