Onset of labour epidural analgesia with low‐dose bupivacaine and different doses of fentanyl

Abstract

This study investigated the effects of different doses of epidural fentanyl on the time to onset of epidural analgesia in women in early labour. We hypothesised that onset of epidural labour analgesia (the primary outcome defined as time in minutes from completion of epidural bolus to the first uterine contraction with a numeric pain rating scale [NPRS] score ≤ 3) would be faster with 100 μg of fentanyl epidural bolus compared with 20 μg or 50 μg. Epidural labour analgesia was initiated with 20 μg of fentanyl (F20 group), 50 μg (F50 group) or 100 μg (F100 group) along with 10 ml bupivacaine 0.08% as the loading dose. We randomly allocated 105 patients, with 35 patients in each group. Median (IQR [range]) time to achieve NPRS ≤ 3 was 18 (11-30 [6-20]) min in F20, 10 (8-19 [4-30]) min in F50 and 10 (6-16 [3-30]) min in F100 groups. There was a significant difference in onset times comparing F100 with F20 (p < 0.001) and F50 with F20 (p = 0.007), but not significantly different comparing F100 with F50 (p = 0.19). The median (IQR [range]) time from the epidural loading dose to first patient controlled epidural analgesia bolus was 61 min (20-165 [20-420]) in F20, 118 min (66-176 [20-396]) in F50 and 150 min (66-214 [30-764]) in F100 groups. This was not statistically significant (p = 0.16) comparing the F20 with the F100 group. There were no significant differences in maternal side-effects, mode of delivery, patient satisfaction scores or neonatal Apgar scores between all groups. We conclude that the 50 μg and 100 μg fentanyl doses were associated with reduced onset times to effective analgesia compared with the 20 μg dose.

The 90% Effective Dose of Sufentanil for Epidural Analgesia in the Early First Stage of Labor: A Double-blind, Sequential Dose-Finding Study

“…Kalra et al 13 found a potency ratio of 1:10 between sufentanil and fentanyl for epidural labor analgesia. Hence, the result of the initiating sufentanil dose in our study and fentanyl 20 μg used by Vedagiri Sai et al 12 may have the same analgesic efficacy with fewer adverse effects. Bernard et al 14 also found that a reduction in sufentanil concentration to 0.156 μg/mL could decrease the pruritus intensity without impeding the quality of labor analgesia, and their recommended sufentanil concentration was close to that of the present study.…”

“…This was not the first time that such a small dose of opioids was used for epidural initiation in the early first stage of labor analgesia. Vedagiri Sai et al 12 used a minimal fentanyl dose of 20 μg for epidural initiation with 10 mL of 0.08% bupivacaine in the early first stage, and the median onset time was 18 minutes with a high success rate. Although these investigators found that administration of 50 and 100 μg of fentanyl could reduce the onset time without increase in the adverse effects, fetal bradycardia incidence did increase compared with that of the 20 μg of fentanyl group.…”