Comparison of the analgesic efficacy of superficial and deep serratus anterior plane blocks in patients undergoing breast cancer surgery: a prospective randomized single blind study

This study aimed to investigate the efficacy of superficial and deep serratus anterior plane blocks (SAPB) for simple mastectomy and modified radical mastectomy (MRM). The primary outcome was cumulative morphine consumption at 24 h. Secondary aims included pain scores, rescue analgesic and antiemetic requirement, nausea and vomiting incidence, and patient satisfaction. Patients were randomized to the superficial or deep SAPB group. Superficial or deep SAPB was applied with 30 ml of 0.25% bupivacaine above or below the serratus anterior muscle, respectively. Postoperative pain control was provided by patient-controlled analgesia (PCA) with morphine. Pain was assessed in the post-anesthesia care unit (PACU), whereas both pain and morphine consumption were evaluated at 2, 6, 12, and 24 h postoperatively. Rescue analgesic and anti-emetic requirement, rescue analgesic dose, PCA bolus request count, nausea and vomiting severity, and satisfaction scores were also evaluated. Cumulative morphine consumption at 24th hour was similar between groups (p = 0.248, effect size = -0.17). Numeric rating scale (NRS) pain scores were slightly lower in the Deep SAPB group at PACU at 6, 12, and 24 h (p < 0.001, p = 0.020, 0.034, and 0.020, respectively; effect sizes = -0.46, -0.33, -0.31, and − 0.33, respectively). Anti-emetic use was lower (p = 0.017, effect size = 0.370), whereas patient satisfaction was higher in the deep SAPB group (p = 0.024, effect size = 0.280). There was no significant difference in PCA bolus request count, rescue analgesic requirement, and dose. Although cumulative morphine consumption was similar, deep SAPB yielded slightly lower NRS scores, reduced the need for antiemetics, and modestly higher patient satisfaction, warranting further studies to determine the clinical advantage. The study was prospectively registered in ClinicalTrials.gov on 29 May 2024 and can be retrieved via https://clinicaltrials.gov/study/NCT06438211 (NCT06438211).