A Randomized Clinical Trial Comparing Different Concentrations of Chloroprocaine with Lidocaine for Activating Epidural Analgesia During Labor

PURPOSE: This study aimed to explore the efficacy and safety of chloroprocaine for activating labor analgesia and the optimal concentration compared to lidocaine. PATIENTS AND METHODS: Ninety-six nulliparous parturients were randomly assigned to three groups: LD group, patients received the conventional initial dose of 6 mL of 1% lidocaine; CP1.5 group, patients received 6 mL of 1.5% chloroprocaine as the initial dose; and CP1.2 group, patients received 7.5 mL of 1.2% chloroprocaine as initial dose. Labor analgesia was maintained in all patients via a programmed intermittent epidural bolus (PIEB). The primary outcome was the analgesia onset time. Secondary outcomes included the visual analog scale (VAS) scores, the interval and duration of uterine contractions during the first 12 contractions, failure to reach adequate analgesia, labor and neonatal outcomes, maternal satisfaction and adverse effects. RESULTS: Parturients in the CP1.5 and CP1.2 groups achieved a shorter onset time than those in the LD group (hazard ratio (HR) = 6.540; 95% confidence interval (CI), 3.503–12.210; P < 0.001 and HR = 3.460; 95% CI, 1.905–6.282; P < 0.001, respectively). The median time (95% CIs) to adequate analgesia was 12.0 (10.9–13.1), 7.0 (6.2–7.8) and 8.0 (7.5–8.5) minutes in the LD, CP1.5 and CP1.2 groups, respectively. PIEB in the CP1.5 group was associated with lower VAS scores, patient-controlled epidural analgesia (PCEA) boluses, and analgesic consumption; a shorter time from epidural initiation to the first PCEA demand; and higher maternal satisfaction scores than the other two groups (P < 0.01). The interval and duration of uterine contractions, labor and newborn outcomes and adverse effects were comparable among the three groups. CONCLUSION: Chloroprocaine provided a faster onset of labor analgesia than lidocaine. Thus, 6 mL of 1.5% chloroprocaine might be a superior volume and concentration regimen to 7.5 mL of 1.2% chloroprocaine for activating labor analgesia. CLINICAL TRIAL REGISTRATION STATEMENT: The study was registered prior to subject enrollment at www.chictr.org.cn (ChiCTR2100049113).