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 mu g with bilateral TAP block using 15 mL of 0.375% ropivacaine per side (TF group) or intrathecal morphine 75 mu g 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) mu g; 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.