The optimal concentration of bupivacaine and levobupivacaine for labor pain management using patient-controlled epidural analgesia: a double-blind, randomized controlled trial.

BACKGROUND:The study aim was to evaluate the efficacy and safety of different low concentrations of two local anesthetics for labor analgesia using patient-controlled epidural analgesia. METHODS:A double-blind, randomized controlled trial recruiting healthy nulliparous women was conducted from 2014 to 2017. Epidural analgesia was provided using local anesthetic and fentanyl. Patients were allocated to six groups, according to the concentration of bupivacaine or levobupivacaine (0.0625%, 0.1%, 0.125%). Analgesic efficacy, vital parameters, and side effects were evaluated at different time points. Satisfaction was evaluated using verbal and written scores. The primary outcome was the total dose of local anesthetic used. RESULTS:Two-hundred-and-thirty-seven cases were analyzed. The total dose of local anesthetic was significantly lower in the two lower concentration groups (P <0.0001). The rate of cesarean section was lower in 0.1% bupivacaine versus 0.1% levobupivacaine (P=0.005), 0.125% levobupivacaine (P=0.049) and 0.125% bupivacaine (P=0.002) groups. Pain breakthrough, patient-controlled and rescue boluses were significantly different between groups (P=0.03, P=0.003 and P <0.0001 respectively). The rate of motor block increased with higher concentrations (P=0.033), but the incidence of other maternal and fetal side effects was not significantly different. Satisfaction with labor analgesia did not differ across groups. Satisfaction score 72 hours after delivery was significantly lower than that two hours after delivery (P <0.0001). CONCLUSIONS:Higher local anesthetic concentration resulted in higher total doses infused and greater motor block. Labor analgesia was less effective when the lowest concentrations were used, but patient satisfaction was unaffected.