Levobupivacaine for Epidural Analgesia in Labor: The Sparing Effect of Epidural Fentanyl

Abstract

Evidence suggests that levobupivacaine has similar pharmacodynamic properties to racemic bupivacaine. We sought to investigate whether this similarity extends to opioid sparing when levobupivacaine is used for epidural analgesia in laboring women by quantifying the effect of fentanyl on the minimum local analgesic concentration (MLAC) of levobupivacaine. One-hundred-six women requesting epidural analgesia for labor pain were recruited in this randomized, double-blinded, up-down sequential allocation study. Each received 20 mL of one of three test solutions: levobupivacaine control, levobupivacaine and fentanyl 2 μg/mL, or levobupivacaine and fentanyl 3 μg/mL. The initial levobupivacaine concentration was 0.07% wt/vol in each group, with subsequent concentrations of levobupivacaine being determined by the response of the previous patient (testing interval 0.01% wt/vol). Efficacy was accepted if the visual analog score decreased to 10 mm or less on a 100-mm scale within 30 min. The MLAC of levobupivacaine in the control group was 0.091% wt/vol (95% CI, 0.052–0.130). Fentanyl at concentrations of 2 μg/mL and 3 μg/mL significantly reduced the MLAC of levobupivacaine to 0.047% wt/vol (95% CI, 0.023–0.072) and 0.050% wt/vol (95% CI, 0.035–0.065), respectively (P < 0.001). A dose-dependent effect was not demonstrated. We conclude that fentanyl significantly reduces levobupivacaine requirements for epidural analgesia in labor. Implications Determination of minimum local analgesic concentrations by the technique of sequential allocation allows the interaction between epidural opioids and local anesthetics to be quantified. This study demonstrates that the addition of fentanyl significantly reduces levobupivacaine requirements for epidural analgesia.