The comparison of clinically relevant doses of intrathecal ropivacaine and levobupivacaine with fentanyl for labor analgesia

Background: Intrathecal labor analgesia using new local anesthetics such as ropivacaine or levobupivacaine becomes more popular by virtues of their safety and decreased motor weakness. However, the analgesic efficacy of the clinically effective intrathecal doses of these new local anesthetics combined with fentanyl has yet to be determined. Methods: Sixty parturients who requested neuraxial analgesia in early active labor were randomly assigned to either ropivacaine (group R, n = 30) or levobupivacaine (group L, n = 30) group. Group R received 3 mg of intrathecal ropivacaine and the group L received 3 mg of intrathecal levobupivacaine mixed with 20 mu g of fentanyl as part of a combined spinalepidural (CSE) technique. The associated block parameters, such as pain scores, duration of analgesia, the highest levels of the sensory block and motor block scores 30 mins after the injection were compared between two groups. Results: Intrathecal ropivacaine offered shorter analgesia (87 +/- 41 min vs. 122 +/- 56 min, P < 0.05) with lower sensory height (T8.5 vs. T6, P < 0.05) and led to lower incidence of complete analgesia (73 vs. 97%, P < 0.05) compared with intrathecal levobupivacaine. Although motor weakness was comparable in both groups, significantly weak perineal squeezing was noticed in Group L (7 of 30 parturients vs. 16 of 30, P < 0.05). Conclusions: Clinically relevant doses of intrathecal levobupivacaine in combination with fentanyl as part of a CSE technique provides more effective analgesia than equivalent doses of intrathecal ropivacaine in early labor, but is accompanied by slight motor weakness.