[A concentration-response observation of hydromorphone combined with ropivacaine in labor analgesia]

Objective: To investigate the median effective dose (ED(50)) of hydromorphone and the appropriate concentration of ropivacaine combined with hydromorphone in epidural labor analgesia. Methods: One hundred and forty nulliparous women undergoing labor selected for delivery with epidural analgesia were enrolled in our hospital from January to June 2016. The first of top 50 women received 0.12% ropivacaine plus 20 μg/ml hydromorphone complex solution, then sequential women were used the modified sequential method to determine the ED(50) and ED(95) of hydromorphone. The other 90 women were randomly divided and receieved 0.08% ropivacaine and 15 μg/ml hydromorphone(H1 group), 0.10% ropivacaine and 15 μg/ml hydromorphone (H2 group), 0.12% ropivacaine and 15 μg/ml hydromorphone (group H3) respectively for epidural labor analgesia. In the course of labor, block levels of epidural analgesia, the Bromage scores, analgesia scores and fetal heart rate-uterine concraction were monitored. In addition, onset time of anesthesia, labor time, mode of delivery, cases of increased oxytocin using, neonatal Apgar score, incidence of nausea and vomiting, itching and fetal heart reduction were recorded. Results: The ED(50) and ED(95) values of hydromorphone were 10.49 (95% CI: 8.89-11.79) and 15.15 (95% CI: 13.25-22.25) μg/ml respectively. The onset time in group H1 was significantly longer than those in group H2 and H3((14.23±3.82) , ( 11.32±2.16), (10.83±2.56)min, respectively), the difference was statistically significant (t=5.854, 6.212, all P<0.05). Analgesic VAS score at 30, 60 and 90 min time points in H1 group was significantly higher than that in H2 group and H3 group (all P<0.05). VAS score at withdrawal in H1 group was significantly higher than that in group H3 ( (3.25±0.75) vs (0.27±0.12) ), the difference was statistically significant ( t=9.314, P<0.05). VAS scores at the fourth, fifth, sixth contractions after analgesia in H1 group were significantly higher than those in H2 and H3 groups (all P<0.05). The incidence of motor nerve block in group H3 was higher than that in group H1 and group H2 (26.67%, 6.66%, 3.33%, respectively), the difference was statistically significant (χ(2)=6.413, 4.320, all P<0.05). Conclusions: 0.10% ropivacaine combined with 15 μg/ml hydromorphone has a good analgesic effect, slight motor block, high safety and worthy clinical application for labor analgesia.