Effects of dural puncture epidural technique at different lumbar interspaces on labor analgesia: a randomized controlled trial

Dural puncture epidural (DPE) technique is increasingly used for labor analgesia, but evidence for optimal lumbar interspace selection remains limited. Although lumbar interspace selection has been reported to influence the onset of conventional epidural analgesia, whether a similar effect occurs with DPE remains unclear. We therefore compared the effects of DPE performed at the L2–3, L3–4, and L4–5 interspaces on labor analgesia. In this single-center, prospective, randomized controlled trial, nulliparous women requesting labor analgesia were randomly assigned in a 1:1:1 ratio to receive DPE at the L2–3, L3–4, or L4–5 interspace. After the initial loading dose, programmed intermittent epidural bolus analgesia was initiated 1 h later. The primary outcome was time to adequate analgesia within 40 min, defined as a Numerical Rating Scale ≤ 3 during uterine contractions. Secondary outcomes included analgesic quality, ropivacaine consumption, block characteristics, maternal and neonatal outcomes, adverse events, and maternal satisfaction. A total of 118 parturients were included in the modified intention-to-treat analysis. Median [IQR] time to adequate analgesia was 11 minutes in the L2–3 group, 13 [7.75–19.75] minutes in the L3–4 group, and 23 [15–34] minutes in the L4–5 group. Compared with L4–5, adequate analgesia was achieved faster with DPE at L2–3 (HR, 4.387; 95% CI, 2.467–7.799; P < 0.001) and L3–4 (HR, 1.976; 95% CI, 1.153–3.385; P = 0.013), with L2–3 also faster than L3–4 (HR, 2.220; 95% CI, 1.333–3.698; P = 0.002). Among the 116 parturients included in the per-protocol analysis, hourly ropivacaine consumption was lower in the L2–3 group than in the L4–5 group (14.7 [14.6–15.3] vs. 15.4 [14.7–16.5] mg/h; P = 0.002). No statistically significant differences in the recorded adverse events were observed among the groups. In nulliparous women, DPE performed at the L2–3 interspace was associated with a faster onset of analgesia than at L3–4 and L4–5 and lower local anesthetic consumption than at L4–5. These findings extend the evidence on interspace-related differences in analgesic onset to DPE labor analgesia. Chinese Clinical Trial Registry (ChiCTR2500101309, Xin Fang, April 23, 2025).