title: Optimal effective concentration of ropivacaine for postoperative analgesia by single-shot femoral-sciatic nerve block in outpatient knee arthroscopy.
abstract: OBJECTIVE
  To compare analgesic and mobility effects of different ropivacaine concentrations in femoral-sciatic nerve block, for postoperative analgesia in knee arthroscopy.
  
  
  METHODS
  Outpatients (American Society of Anesthesiologists physical classification status of I or II), scheduled for elective knee arthroscopy, were randomly allocated to one of seven groups, prospectively investigating different concentrations of ropivacaine (0.12%; 0.14%; 0.16%; 0.18%; 0.20%; 0.22% or 0.50%), for ultrasound-guided femoral-sciatic nerve block procedures for postoperative analgesia. Visual analogue scale (VAS) pain scores and motor block evaluation scales were observed at 4, 8, 16 and 24 h postsurgery.
  
  
  RESULTS
  In total, 105 patients were enrolled; results were analysed for 103. VAS scores for the 0.12%, 0.14% and 0.16% groups were significantly different from the 0.50% group. There were no significant differences between the 0.18%, 0.20%, 0.22% and 0.50% groups: half maximal effective concentrations and 95% maximal effective concentrations of ropivacaine were 0.158 (95% confidence intervals [CI] 0.149, 0.167) and 0.198 (95% CI 0.186, 0.221), respectively. Rates of motor blockade (Bromage score or hip motor function scale > 0) were significantly different between the 0.50% group and all other ropivacaine doses.
  
  
  CONCLUSIONS
  The 0.20% ropivacaine dose for femoral-sciatic nerve block in knee arthroscopy provided satisfactory postoperative analgesia, while preserving ability of motion.
authors.affiliation: Department of Anaesthesiology, The Sixth People's Hospital Affiliated to Shanghai Jiaotong University, Shanghai, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yao
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zeng
authors.forename: Zhi-Hua
authors.initials: ZH
authors.lastname: Jiao
authors.forename: Ai-Zhong
authors.initials: AZ
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Ang
authors.initials: A
authors.lastname: Yu
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D000698:Analgesia; D001182:Arthroscopy; D003710:Demography; D004305:Dose-Response Relationship, Drug; D005260:Female; D005267:Femoral Nerve / Q000601:surgery*; D006615:Hip / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D009407:Nerve Block; D010045:Outpatients; D010149:Postoperative Pain / Q000188:drug therapy*; D000077212:Ropivacaine; D012584:Sciatic Nerve / Q000601:surgery*; D064232:Visual Analog Scale
chemical_list: D000577:Amides; D000077212:Ropivacaine
keywords: Analgesia; femoral–sciatic nerve block; knee arthroscopy; ropivacaine