Role of lumbar puncture level on the onset of epidural labor analgesia: a randomized controlled trial

To compare the speed of achieving painless uterine contractions in parturients undergoing epidural analgesia at different lumbar puncture levels. This study is a randomized controlled trial at a tertiary A hospital with a history of over 80 years in Sichuan Province, China. Parturients aged 22-40 years old scheduled for vaginal delivery under epidural analgesia were recruited. Eligible patients were randomly allocated into lumbar 2-3 (L2-3) or lumbar 3-4 (L3-4) groups. Epidural analgesia was performed through the interspaces according to grouping. The primary outcome was the percentage of painless uterine contractions 15 min after the initiation of analgesia. The secondary outcomes included the percentage of painless status at 5 and 10 min, sensory block plane, motor block evaluation, adverse events of parturients, epidural analgesic consumption, Apgar score, and the parturients' evaluation of analgesia. Between April 2023 and August 2023, a total of 150 women were finally recruited, and 136 of them were analyzed (68 in each group). In comparison with the L3-4 groups, there was a significantly larger proportion of painless uterine contractions at 5, 10, and 15 min after analgesia initiation in the L2-3 group (20.6% vs. 7.4%, 52.9% vs. 26.5%, and 80.9% vs. 64.7%, P = .026, .002, and .034, respectively). Similarly, the pain scores were lower in the L2-3 group at 5, 10, and 15 min than that in the L3-4 group (5(4,7) vs. 6(5,7), 3(2,5) vs. 4(3,6), and 2(1,3) vs. 3(2,5), P = .006, .004, and .020, respectively). Furthermore, puncturing through the L2-3 interspace contributed to a higher evaluation of parturients to the analgesia procedure (9(8,9) vs. 8(8,9), P