Oblique subcostal transverse abdominis plane block for postoperative pain control in patients undergoing open sublay mesh hernia repair: a prospective double-blind randomized placebo-controlled clinical trial

Background A bilateral oblique subcostal transverse abdominis plane block may help provide perioperative analgesia and reduce opioid use in patients undergoing sublay mesh hernia repair, but its clinical value is unclear. Methods In a single-centre, prospective, placebo-controlled, double-blind study, patients scheduled for sublay mesh hernia repair were randomized to receive oblique subcostal transverse abdominis plane blocks with either 60 ml of 0.375% ropivacaine (n=19) or isotonic saline (placebo, n=17). The primary outcome was patient-controlled total morphine consumption at 8:00 p.m. on the second postoperative day (POD), while secondary outcomes included the total morphine consumption during the post-anesthesia care unit stay and the occurrence of adverse events. Results Total morphine consumption at 8:00 p.m. on the second POD was higher in patients receiving ropivacaine (39 mg, IQR 22, 62) compared with placebo (24 mg, IQR 7, 39), p value = 0.04. In contrast, the ropivacaine group received 2 mg less morphine during the post-anesthesia care unit stay (4 mg, IQR: 4, 9 mg vs 2 mg, IQR: 2,6 mg, p = 0.04). Patients receiving ropivacaine used more morphine (8:00 p.m. on the first POD until 8:00 a.m. on the second POD: 8 mg, IQR: 4, 18 mg vs 2 mg, IQR: 0, 9 mg, p = 0.01) and reported higher maximum pain scores since the last assessment (8:00 a.m. on the second POD: 5, IQR: 4, 7 vs 4, IQR: 3, 5, p = 0.03). There were no differences in adverse events between groups. Conclusions Bilateral oblique subcostal transverse abdominis plane blocks in patients undergoing sublay mesh hernia repair were not associated with a prolonged reduction in patient-controlled total morphine consumption in the evening of the second POD in this study. Rebound pain might explain the additional excess opioid required by the ropivacaine group.