Purpose: Worldwide, there are only few studies focusing on labor analgesia on the MLAC (minimum local analgesic concentration) or EC50 (median effective concentration) of sufentanil and ropivacaine. Therefore, we determine the MLAC or EC50 of sufentanil and ropivacaine for epidural analgesia by using an up-down sequential allocation and survey its adverse effect in a prospective blinded randomized trial.
Methods: Sixty nulliparous full-term parturients who required labor analgesia were recruited and randomly divided into the sufentanil and ropivacaine groups. The formulation was 25 μg sufentanil combined with 0.1% ropivacaine (added 0.9% normal saline to 75 ml). According to the response of a previous parturient, the dosage of sufentanil was increased or decreased by 5 μg in the sufetanil group; meanwhile, we also administrated an initial concentration of 0.1% ropivacaine combined with 22.5 μg sufentanil (added 0.9% normal saline to 75 ml) in the ropivacaine group. The concentration of ropivacaine was increased or decreased by 0.01% following the response of the previous parturient. The Brownlee up-down sequential allocation was used to estimate the MLAC of epidural ropivacaine and its 95% confidence intervals in labor analgesia.
Findings: There were no significant changes for the two groups, including for age, height weight, active stage, second stage of labor, and gestational weeks (P = 0.769, 0.900, 0.603, 0.441, 0.577, and 0.695, respectively). The VAS scores of the parturient decreased to varying degrees (P < 0.0001) after labor analgesia compared with VAS before labor analgesia, and the most effective analgesia was reached in 60 min. The EC50 dose of epidural ropivacaine combined with 0.3 μg/mL sufentanil was 0.09687%, and the 95% CI was 0.08944%~0.1043%. Five parturients had PONV, and the incidence rate was 16.7%; one parturient had pruritus, so the incidence rate was 3.3%. The EC50 dose of epidural sulfetanil combined with 0.1% ropivacaine was 18.76 μg with a 95% confidence interval of 13.5-24.48 μg. There were no significant differences in the active stage, second stage of labor, and maternal and fetal hemodynamic data between the two groups. Notably, the Apgar scores for 1 min and 5 min were 10 scores for almost all of these patients. There were no significant differences between the two groups for maternal and fetal side effects, which had very low incidence rates.
Implications: The MLAC of epidural sufentanil or ropivacaine could provide satisfactory and safe analgesia for parturients while having a low incidence rate of side effects.
Keywords: EC50; Ropivacaine; dose effect relation; epidural labor analgesia; sufentanil.
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