Introduction The intertransverse process (ITP) block mimics the thoracic paravertebral block and allegedly ameliorates hemithoracic postoperative pain. However, concerning major reconstructive breast cancer surgery the modality has never been tested against placebo in a randomized clinical trial. We aimed to assess the efficacy of the multiple-injection ITP block and hypothesized that the blockade would reduce postoperative opioid consumption.

Methods We screened 58 patients with breast cancer scheduled for unilateral subpectoral implant-based primary breast reconstruction, involving mastectomy with complete fascial dissection of the major pectoral muscle. A randomization procedure allowed for the allocation of 36 patients to receive either unilateral multiple-injection active ITP block (0.5% ropivacaine 3×10 mL) or placebo ITP block (isotonic saline 3×10 mL) at T2, T4, T6 in a prospective, blinded, clinical trial. The primary outcome was total opioid consumption within the first 24 postoperative hours. Secondary outcomes included opioid consumption at 4-hour intervals, postoperative pain, patient satisfaction with block application, time to first opioid, ambulation and discharge, opioid-related side effects, and quality of recovery.

Results Opioid consumption within the first 24 postoperative hours showed no significant reduction when comparing the active and placebo group median (IQR): 75.0 mg (45–135) vs 62.5 mg (30–115), p=0.5, respectively. We did not find any consequential clinically relevant results of the secondary outcomes.

Conclusions Following major reconstructive breast cancer surgery, a preoperative multiple-injection ITP block neither reduces 24-hour opioid consumption postoperatively nor promotes substantial clinical positive outcomes.