Impact of Transversus Abdominis Plane Block With Bupivacaine or Ropivacaine Versus Intrathecal Morphine on Opioid-related Side Effects After Cesarean Delivery A Meta-analysis of Randomized Controlled Trials

Objectives: Intrathecal morphine (ITM) is frequently associated with side effects such as postoperative nausea and vomiting (PONV) and pruritus. The aim of this meta-analysis was to compare the impact of transversus abdominis plane (TAP) block versus ITM on side effects following cesarean delivery. Materials and Methods: PubMed, Embase, Web of Science, and CENTRAL were searched for randomized controlled trials that compared TAP with ITM for cesarean delivery. The primary outcomes were opioid-related side effects. The secondary outcomes included pain scores, opioid consumption, patient satisfaction, and time to the first analgesia request. Results: Seven studies involving 660 patients were included. TAP blocks were performed with bupivacaine or ropivacaine. There was less PONV with TAP versus ITM (risk ratio [RR]=0.45, 95% confidence interval [CI]: 0.33-0.63, PI (2)=0%), but no significant difference in pruritus (RR=0.76, 95% CI: 0.49-1.18, P=0.22; I (2)=78%) and sedation (RR=0.44, 95% CI: 0.19-1.00, P=0.05; I (2)=0%). TAP had a greater morphine consumption in 24 hours (mean difference: 5.80 mg; 95% CI: 1.38-10.22 mg, P=0.01; I (2)=89%) and higher pain score at rest at 6 hours (mean difference: 0.70, 95% CI: 0.39-1.02, PI (2)=56%), but similar pain at rest at 24 hours and on movement compared with ITM. No differences were found in time to first analgesia and patient satisfaction. Discussion: Compared with ITM, TAP block is associated with less PONV but inferior early analgesia after cesarean delivery. However, the heterogeneity among the studies highlights the need for more well-designed studies to obtain more robust conclusions.