Effects of transversus abdominis plane blocks after hysterectomy: a meta-analysis of randomized controlled trials

Background: Transversus abdominis plane (TAP) block can provide effective analgesia for abdominal surgery. However, many randomized controlled trials (RCTs) have shown controversial results in hysterectomy. We conducted a meta-analysis of RCTs to investigate the effectiveness of TAP block after hysterectomy. Methods: Studies were gathered from PubMed, MEDLINE, EMBASE, Cochrane Library, Web of Science, and ClinicalTrials. gov databases up to March 2018. RCTs involving TAP blocks in women undergoing hysterectomy were selected. The primary outcome of mean 24 hours morphine consumption and other outcomes, such as time to first request for analgesic, rest, and pain scores on movement at different times, and rates of nausea and vomiting, were compared between TAP block and no or sham block groups. Results: A total of 841 participants were included in the 13 selected RCTs. Compared with no or sham blocks, TAP block reduced mean 24-hour morphine consumption in abdominal hysterectomy (AH) (weighted mean difference [WMD] -10.77 mg, P= 0.04) but not in laparoscopic hysterectomy (LH)/robotic-assisted hysterectomy (RH) (WMD -1.39 mg, P= 0.24). TAP block in AH prolonged analgesic time and reduced nausea and vomiting rates. TAP block also reduced the postoperative pain score at rest and on movement at different times in the AH subgroup, but it did not significantly reduce the postoperative pain score at rest, 6-8, and 24 hours, as well as the pain score on movement at 2, 6-8, and 24 hours in the LH/ RH subgroup. Conclusion: TAP block is an effective analgesic for AH. TAP block can reduce postoperative morphine consumption in AH and pain scores at rest and on movement for AH without increasing side effects. However, TAP block has limited analgesic effects for women undergoing LH/ RH, as it does not reduce postoperative morphine consumption and pain scores at rest and on movement.