Opioid-Sparing Effects of Transversus Abdominis Plane Block in Elective Hysterectomy: A Systematic Review and Meta-Analysis.

Posthysterectomy pain is caused by abdominal incision and traumatic manipulation of the intra-abdominal structures. Optimal pain management consists of a multimodal pain regimen combined with transversus abdominis plane (TAP) block. We searched PubMed, EMBASE, and Cochrane Database for randomized controlled trials evaluating the opioid-sparing effects of TAP block in patients undergoing hysterectomy. The primary outcome was morphine consumption in the perioperative phase extending to 48 hours after surgery. The secondary outcomes were pain scores at rest and during coughing, time of first postoperative analgesia, and incidence of postoperative nausea and vomiting (PONV) and sedation. Twenty-three trials were selected consisting of 1,554 patients. Morphine consumption showed a reduction of 3.6 mg intraoperatively (mean difference [MD], -3.57; 95% CI, -6.88 to -0.25); 2.9 mg in the recovery room (MD, -2.86; 95% CI, -5.55 to -0.15); 3.4 mg at 24 hours (MD, -3.43; 95% CI, -6.77 to -0.09), and 29 mg at 48 hours (MD, -28.68; 95% CI, -44.35 to -13.01) after surgery in favor of TAP block. Pain scores were lower at rest, and the incidence of PONV and sedation were reduced. Although opioid-sparing effects of TAP block were significant perioperatively, its clinical application is debatable because of substantial heterogeneity across studies.