Paravertebral versus Pectoralis-II (Interpectoral and Pectoserratus) Nerve Blocks for Postoperative Analgesia after Nonmastectomy Breast Surgery: A Randomized, Controlled, Observer-masked Noninferiority Trial

Background: Pectoralis-II and paravertebral nerve blocks are both used to treat pain after breast surgery. Most previous studies involving mastectomy identified little difference of significance between the two approaches. Whether this is also accurate for nonmastectomy procedures remains unknown. Methods: Participants undergoing uni- or bilateral nonmastectomy breast surgery anticipated to have at least moderate postoperative pain were randomized to a pectoralis-II or paravertebral block (90 mg ropivacaine per side for both). Surgeons and recovery room staff were masked to treatment group assignment, and participants were not informed of their treatment group. Injectate for pectoralis-II blocks was ropivacaine 0.3% (30 ml) per side. Injectate for paravertebral blocks was ropivacaine 0.5% (9 ml in each of two levels) per side. This study hypothesized that pectoralis-II blocks would have noninferior analgesia (numeric rating scale) and noninferior cumulative opioid consumption within the operating and recovery rooms combined (dual primary outcomes). The study was adequately powered with n = 100, but the target enrollment was raised to n = 150 to account for higher-than-anticipated variability. Results: The trial was ended prematurely with 119 (79%) of the original target of 150 participants enrolled due to (masked) surgeon preference. Within the recovery room, pain scores were higher in participants with pectoralis-II (n = 60) than paravertebral blocks (n = 59): median [interquartile range], 3.3 [2.3, 4.8] versus 1.3 [0, 3.6] (95% CI, 0.5 to 2.6; P < 0.001). Similarly, intravenous morphine equivalents were higher in the pectoralis-II group: 17.5 [12.5, 21.9] versus 10.0 mg [10, 20] (95% CI, 0.1 to 7.5; P = 0.004). No block-related adverse events were identified in either group. Conclusions: After nonmastectomy breast surgery, two-level paravertebral blocks provided superior analgesia and opioid sparing compared with pectoralis-II blocks. This is a contrary finding to the majority of studies in patients having mastectomy, in which little significant difference was identified between the two types of blocks.