ED90 of Sufentanil in Epidural Initiation for Labor Analgesia in Latent Phase and Active Phase During the First Labor Stage

Background: The standard solutions for epidural labor analgesia include both local anesthetics and opioids. The concept of the standard epidural use of local anesthetics in labor analgesia has shifted from high concentrations to high volumes with low concentrations. However, the optimal dosage of opioids needed to initiate and maintain epidural labor analgesia in different phases during the first labor stage has rarely been studied.

Objective: The present study aimed to determine the optimal sufentanil dose for epidural initiation in the latent and active phases during the first stage of labor.

Study design: A prospective, double-blind, sequential dose-finding study.

Setting: A Class A tertiary obstetrics and gynecology hospital.

Methods: The study included 80 nulliparae with cervical dilatation of 2-4 cm and 5-6 cm, with 40 nulliparae in each group. A research dose of sufentanil combined with ropivacaine 13 mg in epidural initiation with a volume of 15 mL was administered to the puerperant. A 1-microgram sufentanil dose and a 2.5-micrograms sufentanil dose were used for the first puerperant of each group. The dose of sufentanil for the subsequent puerperant was determined by the response of the previous puerperant according to the biased coin up-and-down design in each trial. The primary outcome was a visual analog scale score of <= 3 at 15, 30, and 45 minutes after epidural administration, including the given dose of sufentanil. According to the response of each puerperant, the 90% effective doses and their 95% confidence intervals were estimated by isotonic regression and bootstrapping according to the response of each puerperant.

Results: The 90% effective doses of sufentanil for puerperants were 1.91 micrograms (95% confidence intervals 1.82-2.35 micrograms) and 4.90 micrograms (95% confidence intervals 4.82-5.35 micrograms) in epidural initiation in the latent and active phases, respectively. The 90% effective doses were 62.5% (95% confidence intervals 50.8-64.0%) lower in the latent phase than that in the active phase during the first stage of labor.

Limitations: Both spontaneous labor and induced labor were included in this study, and the degree of pain in these 2 types of labor is different. Further, only nulliparae were recruited in the study.

Conclusions: Different sufentanil doses should be adopted in epidural initiation in different phases during the first stage of labor due to the large differences in the demand for sufentanil.