title: Dose-dependent reduction of the minimum local analgesic concentration of bupivacaine by sufentanil for epidural analgesia in labor.
abstract: BACKGROUND
  The minimum local analgesic concentration (MLAC) has been defined as the median effective local analgesic concentration in a 20-ml volume for epidural analgesia in the first stage of labor. The aim of this study was to determine the local anesthetic-sparing efficacy of epidural sufentanil by its effect on the MLAC of bupivacaine.
  
  
  METHODS
  In this double-blind, randomized, prospective study, 147 parturients at < or = 7 cm cervical dilation who requested epidural analgesia were allocated to one of four study groups. After a lumbar epidural catheter was placed, study participants received 20 ml bupivacaine (n = 38), bupivacaine with sufentanil 0.5 microg/ml (n = 38), bupivacaine with sufentanil 1 microg/ml (n = 33), or bupivacaine with sufentanil 1.5 microg/ml (n = 38). The concentration of bupivacaine was determined by the response of the previous patient using up-down sequential allocation. The analgesic efficacy was assessed using 100-mm visual analog pain scores, with < or = 10 mm within 30 min defined as effective.
  
  
  RESULTS
  The MLAC of bupivacaine alone was 0.104% wt/vol (95% CI, 0.090-0.117). The addition of sufentanil at doses of 0.5 microg/ml, 1 microg/ml, and 1.5 microg/ml resulted in significant reductions (P < 0.0001) in the MLAC of bupivacaine to 0.048% wt/vol (95% CI, 0.030- 0.065), 0.021% wt/vol (95% CI, 0-0.055), and 0.009% wt/vol (95% CI, 0-0.023), respectively.
  
  
  CONCLUSIONS
  This study showed a significant (P < 0.0001) dose-dependent reduction in the MLAC ofbupivacaine by sufentanil.
authors.affiliation: Department of Anesthesiology, Women's Hospital, University of Michigan Medical Center, Ann Arbor, USA. lpolley@umich.edu
authors.forename: L S
authors.initials: LS
authors.lastname: Polley
authors.forename: M O
authors.initials: MO
authors.lastname: Columb
authors.forename: D S
authors.initials: DS
authors.lastname: Wagner
authors.forename: N N
authors.initials: NN
authors.lastname: Naughton
mesh_terms: D015360:Analgesia, Epidural; D016362:Analgesia, Obstetrical; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000779:Anesthetics, Local / Q000493:pharmacokinetics*; D002045:Bupivacaine / Q000493:pharmacokinetics*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D011247:Pregnancy; D011446:Prospective Studies; D017409:Sufentanil / Q000494:pharmacology*
chemical_list: D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D017409:Sufentanil; D002045:Bupivacaine