Effects of ropivacaine combined with fentanyl for epidural labor analgesia

Objective To evaluate effects of ropivacaine combined with different concentrations of fentanyl for epidural labor analgesia. Methods In this multicenter double-blinded randomized study 128 parturients at full term and 2-3 cm of cervical dilatation who requested epidural analgesia were randomly allocated to one of 4 groups: group F0 received epidural ropivacaine alone (n = 33); group F1 received epidural ropivacaine with fentanyl 1 μg·ml-1 (n = 30) ; group F2 epidural ropivacaine + fentanyl 2μg·ml-1(n = 33) and group F3 epidural ropivacaine + fentanyl 3 μg·ml-1(n = 32). Epidural catheter was placed at L2,3 and advanced 4 cm into the epidural space in cephalad direction. A bolus of 15 ml of ropivacaine alone or with fentanyl was given after correct epidural placement was confirmed. EC50 of epidural ropivacaine was determined by up-and-down sequential experiment. The initial concentration of epidural ropivacaine was 0. 12% . If effective the next parturient received ropivacaine of lower concentration; if ineffective the ropivacaine concentration was increased. Each time the concentration of epidural ropivacaine increased/decreased by 0.01% . The analgesia was assessed using VAS score (0-10 0 = no pain, 10 = worst pain) . If VAS score was less than 3 within 30 min of ropivacaine administration, analgesia was defined as effective. EC50 of ropivacaine was calculated according to Dixon and Massey. Results Four of the 128 parturients enrolled were excluded because of uncertain results of interrupted observation. The EC50 of epidural ropivacaine for labor analgesia and the 95% confidence interval (95% CI) of EC50 were 0.110% (95% CI 0.109 0%-0.111 6%) in group F0; 0.089% (95% CI 0.087 7%-0.091 1%) in group F1; 0.073% (95% CI 0. 071 7%-0.0744%) in group F2 and 0.060% (95% CI 0.056 0%-0.634%) in group F3 respectively. The EC50 was significantly higher in group F0 than in group F1, F2 and F3 (P0.05). There was no significant decrease in SP within 30 min after ropivacaine administration as compared with SP before epidural analgesia, but the heart rates of the parturients and fetuses were significantly decreased within 30 min of analgesia in group F0, F1 and F2 (P0.05 or 0.01) . There was no significant difference in motor block among the 4 groups (P0.05) . The incidence of side-effect was significantly higher in group F3 than in group F0(P0.05) .Conclusions The epidural labor analgesia of ropivacaine is enhanced by additional fentanyl 1-3 μg·ml-1. Fentanyl at concentration of 1-2 μg·ml-1 enhances analgesic effect of epidural ropivacaine with less side-effect.