Effect of adding a superficial parasternal intercostal plane block to the serratus anterior plane block on postoperative analgesic outcomes in breast cancer surgery: a prospective, randomized, double-blind trial

Background: Breast cancer surgery is frequently associated with moderate to severe postoperative pain. While the serratus anterior plane block (SAPB) provides effective anterolateral chest wall analgesia, it may inadequately cover the anterior intercostal nerve branches. This study aimed to determine whether adding a superficial parasternal intercostal plane block to SAPB improves postoperative opioid consumption, pain scores, and dermatomal sensory coverage. Methods: In this prospective, randomized, double-blind trial, 64 patients aged 18–65 years undergoing elective breast surgery were randomly allocated into two groups. Group S (n = 32) received a preoperative SAPB with 30 mL of 0·25% bupivacaine combined with a parasternal injection of 10 mL saline. Group S + P (n = 32) received a SAPB with 30 mL of 0·25% bupivacaine plus a parasternal block with 10 mL of 0·25% bupivacaine. All patients were managed with an identical multimodal postoperative analgesia protocol. The primary outcome was postoperative opioid consumption. Secondary outcomes included visual analogue scale (VAS) pain scores, dermatomal sensory analysis and side effects. Results: Baseline demographic characteristics and surgical variables were comparable between groups (p > 0·05). Sensory blockade of the T3, T4, and T5 dermatomes was significantly more frequent in the S + P group than in the S group (p < 0·05). However, postoperative VAS pain scores at rest and during movement, as well as total opioid consumption, were comparable between groups (p > 0·05). Conclusions: Although the addition of a superficial parasternal intercostal plane block to SAPB resulted in wider anterior chest wall dermatomal coverage, it did not confer additional benefit in terms of postoperative pain scores or opioid consumption under a multimodal analgesia regimen. These findings suggest that SAPB-based strategies, when combined with systemic analgesics, may provide sufficient postoperative analgesia in patients undergoing mastectomy. © The Author(s) 2026.