Analgesic efficacy of postoperative bilateral, ultrasound-guided, posterior transversus abdominis plane block for laparoscopic colorectal cancer surgery: a randomized, prospective, controlled study

BACKGROUND: We assessed whether a postoperative bilateral, ultrasound-guided, posterior transversus abdominis plane (TAP) block could reduce 24 h rescue tramadol requirement compared with placebo in patients undergoing elective laparoscopic colorectal cancer surgery. METHODS: Patients scheduled to undergo elective laparoscopic surgery following the diagnosis of colorectal cancer were included in this study and randomized into Group and Group Control. The patients received a postoperative bilateral, ultrasound-guided, posterior TAP block in either 20 mL of 0.5% ropivacaine (Group TAP) per side or an equivalent volume of normal saline (Group Control). The primary outcome was the cumulative consumption of rescue tramadol within 24 h after the surgery. Secondary endpoints included (1) resting and movement numerical rating scale (NRS) pain scores at 2, 4, 6, 12, 24, 48, and 72 h; (2) incidences of related side effects; (3) time to the first request for rescue tramadol; (4) patient satisfaction regarding postoperative analgesia; (5) time to restoration of intestinal function; (6) time to mobilization; and (7) the length of hospital stay. RESULTS: In total, 92 patients were randomized, and 82 patients completed the analysis. The total rescue tramadol requirement (median [interquartile range]) within the first 24 h was lower in Group TAP (0 [0, 87.5] mg) than in Group Control (100 [100, 200] mg), P < 0.001. The posterior TAP block reduced resting and movement NRS pain scores at 2, 4, 6, 12, and 24 h after surgery (all P < 0.001) but showed similar scores at 48 h or 72 h. A higher level of satisfaction with postoperative analgesia was observed in Group TAP on day 1 (P = 0.002), which was similar on days 2 (P = 0.702) and 3 (P = 0.551), compared with the Group Control. A few incidences of opioid-related side effects (P < 0.001) and a lower percentage of patients requiring rescue tramadol analgesia within 24 h (P < 0.001) were observed in Group TAP. The time to the first request for rescue analgesia was prolonged, and the time to mobilization and flatus was reduced with a shorter hospital stay in Group TAP as compared with Group Control. CONCLUSIONS: A postoperative bilateral, ultrasound-guided, posterior TAP block resulted in better pain management and a faster recovery in patients undergoing laparoscopic colorectal cancer surgery, without adverse effects. TRIAL REGISTRATION: The study was registered at http://www.chictr.org.cn (ChiCTR-IPR-17012650; Sep 12, 2017).