Postoperative Analgesia by a Transversus Abdominis Plane Block Using Different Concentrations of Ropivacaine for Abdominal Surgery A Meta-Analysis

Background: Transversus abdominis plane block (TAPB) has been proven to be an effective means of postoperative anesthesia, but the optimum effective concentration of ropivacaine warrants further research. Objective: This study aimed to identify the optimal ropivacaine concentration of TAPB using a meta-analysis. Materials and Methods: This study consisted of a meta-analysis of randomized controlled trials (RCTs). We searched online data-bases, including PubMed, Embase, the Cochrane Database of Systematic Reviews, and Web of Science. RCTs investigating the 24-hour postoperative opioid consumption and the rest and dynamic pain scores 2, 12, and 24 hours after surgery were included in this analysis. We also assessed opioid-related side-effects and patient satisfaction 24 hours after surgery. Results: Nineteen RCTs (1217 patients) were included in this meta-analysis, which showed that only TAPB with 0.375% and 0.5% ropivacaine was able to reduce opioid consumption 24 hours after surgery by weighted mean differences of -6.55 and -4.44mg (morphine IV equivalents), respectively (P < 0.05). A meta-regression analysis did not reveal an association between the local anesthetic dose (in mg), surgery, anesthesia, block timing, and the TAPB effect on opioid consumption. Ropivacaine concentrations of 0.375% and 0.5% reduced the 2-hour postoperative pain score and reduced the incidence of nausea and vomiting, but this analgesic effect disappeared at 12 and 24 hours. Only TAPB with 0.375% ropivacaine improved the degree of satisfaction 24 hours after surgery (weighted mean difference of 0.87 [0.08-1.66], P = 0.03). Conclusion: In terms of efficacy and safety, the use of 0.375% ropivacaine for TAPB is preferred in the clinical work.