Transversus abdominis plane block combined with intrathecal fentanyl versus intrathecal morphine for post-cesarean analgesia: a randomized non-inferiority clinical trial

Background Intrathecal morphine is the standard for post-cesarean analgesia but often causes pruritus and may be unavailable in resource-limited settings. This study assessed whether a combination of bilateral transversus abdominis plane (TAP) block and intrathecal fentanyl provides non-inferior analgesia compared with intrathecal morphine following cesarean delivery within the multimodal analgesia context. Methods Eighty mothers were randomized to receive either intrathecal fentanyl 10 µg with bilateral TAP block using 15 mL of 0.375% ropivacaine per side (TF group) or intrathecal morphine 75 µg with a saline sham block (M group). All patients received standard multimodal analgesia. Primary outcome was pain score with movement at 24 hours postoperatively, with a non-inferiority margin of 1 on the numeric rating scale. Secondary outcomes included opioid consumption, time to first opioid, pruritus, nausea/vomiting, patient satisfaction, and neonatal outcomes. Results The mean pain score with movement at 24 hours was 5.4 in the TF group and 4.8 in the M group (mean difference (95% CI), 0.6 (−0.3 to 1.5), p=0.202), with the upper margin of 95% CI exceeding the non-inferior margin. Postoperative fentanyl consumption was higher in the TF group (median (IQR), 585 (390–745) vs 140 (55–405) µg; p<0.001). Pruritus was more frequent in the M group (60% vs 10%; p<0.001). Conclusions Bilateral TAP block with intrathecal fentanyl is not non-inferior to intrathecal morphine for post-cesarean analgesia. However, intrathecal morphine was associated with a higher incidence of pruritus, suggesting TAP block with intrathecal fentanyl as a suitable alternative when reducing pruritus is a priority. Trial registration number NCT04824274 .