title: On the ropivacaine-reducing effect of low-dose sufentanil in intrathecal labor analgesia.
abstract: BACKGROUND
  Combining ropivacaine with sufentanil for intrathecal (i.t.) analgesia in labor is well recognized, but information on dosing is limited. This study aimed to determine the ED 50 of i.t. ropivacaine and to assess the effect of adding defined low doses of sufentanil.
  
  
  METHODS
  This was a two-phase, double-blind, randomized and prospective study. One hundred and fifteen parturients receiving combined spinal epidural analgesia were allocated to one of four groups to receive ropivacaine or sufentanil alone or in combination. In phase one, sufentanil dose-response was calculated using logistic regression. In phase two, ED 50 of ropivacaine and of the combination with a fixed dosage of sufentanil at ED 20 and ED 40 was evaluated using the technique of up-down sequential allocation. Analgesic effectiveness was assessed 15 min after injection using a 100 mm visual analog scale, with <10 mm lasting for 45 min defined as effective. Furthermore, side effects and duration were recorded.
  
  
  RESULTS
  The ED 50 of i.t. ropivacaine was 4.6 mg [95% confidence intervals (95% CI) 4.28, 5.31]. Adding sufentanil at ED 20 significantly decreased the ED 50 of i.t. ropivacaine to 2.1 mg (95%CI 1.75, 2.5) (P<0.005); at ED 40, the reduction was similar (P<0.005). Combining sufentanil with ropivacaine resulted in a dose-independent prolongation of analgesia. Besides pruritus, which was well tolerated, there were no differences in side effects.
  
  
  CONCLUSIONS
  Adding sufentanil at ED 20 results in a more than 50% dose-sparing effect of ropivacaine and considerably prolongs analgesia. Increasing dosage implicates no clinical benefit.
authors.affiliation: Department of Anesthesia, General Intensive Care and Pain Control, Medical University Vienna, Vienna, Austria. clemens.ortner@meduniwien.ac.at
authors.forename: C M
authors.initials: CM
authors.lastname: Ortner
authors.forename: M
authors.initials: M
authors.lastname: Posch
authors.forename: B
authors.initials: B
authors.lastname: Roessler
authors.forename: P
authors.initials: P
authors.lastname: Faybik
authors.forename: K
authors.initials: K
authors.lastname: Rützler
authors.forename: J
authors.initials: J
authors.lastname: Grabovica
authors.forename: O
authors.initials: O
authors.lastname: Kimberger
authors.forename: B
authors.initials: B
authors.lastname: Gustorff
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D016362:Analgesia, Obstetrical; D000775:Anesthesia, Spinal; D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D016015:Logistic Models; D011247:Pregnancy; D000077212:Ropivacaine; D017409:Sufentanil
chemical_list: D000577:Amides; D018686:Anesthetics, Intravenous; D000779:Anesthetics, Local; D000077212:Ropivacaine; D017409:Sufentanil