Duration of analgesic effectiveness after the posterior and lateral transversus abdominis plane block techniques for transverse lower abdominal incisions: a meta-analysis

Both posterior and lateral transversus abdominis plane (TAP) block techniques provide effective early (012 h) postoperative analgesia after transverse incision surgery. However, whether either technique produces prolonged analgesia lasting beyond 12 h remains controversial. This meta-analysis examines the duration of analgesia associated with posterior and lateral TAP blocks in the first 48 h after lower abdominal transverse incision surgery. We retrieved randomized controlled trials (RCTs) investigating the analgesic effects of TAP block compared with control in patients undergoing lower abdominal transverse incision surgery. Outcomes sought included interval postoperative i.v. morphine consumption and also rest and dynamic pain scores at 12, 24, 36, and 48 h postoperatively. Opioid-related side-effects and patient satisfaction at 24 and 48 h were also assessed. The 1224 h interval morphine consumption was designated as a primary outcome. Twelve RCTs including 641 patients were analysed. Four trials examined the posterior technique and eight assessed the lateral technique. Compared with control, the posterior TAP block reduced postoperative morphine consumption during the 1224 h and 2448 h intervals by 9.1 mg (95 CI: 16.83, 1.45; P0.02) and 5 mg (95 CI: 9.54, 0.52; P0.03), respectively. It also reduced rest pain scores at 24, 36, and 48 h, and also dynamic pain scores at 12, 24, 36, and 48 h. Differences were not significant with the lateral TAP block. Based on the comparisons with control, the posterior TAP block appears to produce more prolonged analgesia than the lateral TAP block. Future RCTs comparing these two techniques are required to confirm our findings.