Abstract: AIM: To investigate the ED₅₀ of butorphanol combined with 0.15% ropivacaine and the most effective concentration of ropivacaine combined with butorphanol in labor epidural analgesia.METHODS: 121 nulliparous women undergoing labor selected for delivery with epidural analgesia. The first of the top 31 woman received 0.15% ropivacaine plus 20 μg/mL butorphanol 10 mL, the next woman's dose of the butorphanol was determined by a modification of sequential method. The other 90 women received 0.08% ropivacaine and butorphanol 16 μg/mL (Group B1), 0.10% ropivacaine and butorphanol 16 μg/mL (group B2), 0.12% ropivacaine and butorphanol 16 μg/mL(group B3) respectively.In the course of labor, block levels of epidural analgesia, the Bromage scores, Ramsay scores, fetal heart rate-uterine contraction were monitored. In addition, onset time of anesthesia, labor time, the cases of oxytocin using, Apgar scores of neonates and side-effect were recorded.RESULTS: There were no significant differences in age, height, weight and gestational weeks in every woman.The ED₅₀ of butorphanol was 14.79 μg/mL (95%CI 13.91～15.61 μg/mL). The ED₉₅ of butorphanol was 16.84 μg/mL (95%CI 15.86～20.97 μg/mL). The onset of anesthesia in group B1 was significantly longer than other two groups (P<0.05). The VAS scores at 30 min, 60 min, 90 min after injection in group B1 was significantly higher than those in other two groups(P<0.05), and the VAS scores when drug withdraw in group B1 was significantly higher than those in group B3(P<0.05). Group B3 showed higher motor block than other two groups (P<0.05).CONCLUSION: 0.10% ropivacaine combined with butorphanol 16 μg/mL is the most effective for epidural analgesia in labor. It is worth clinical application for its kind analgesic effect, slight motor block and high safety.

Key words: Ropivacaine, Butorphanol, Labor analgesia