The combination of interpectoral plane and superficial serratus anterior plane blocks for the prevention of persistent pain after total mastectomy: a triple-blinded, randomised, placebo-controlled trial.

INTRODUCTION Chronic post-mastectomy pain may be preventable with regional analgesia. Ultrasound-guided fascial plane blocks are accepted alternatives to paravertebral block for patients undergoing mastectomy. While fascial plane blocks may be used individually, combining them may be more effective. This study tested the hypothesis that combining interpectoral plane and superficial serratus anterior plane blocks would reduce the incidence of chronic post-mastectomy pain compared with the superficial serratus anterior plane block alone. METHODS We enrolled adult women scheduled to undergo total mastectomy with or without lymph node dissection. The intervention group received both interpectoral plane and superficial serratus anterior plane blocks with 0.375% ropivacaine pre-operatively. The control group received saline as the interpectoral plane injection and a superficial serratus anterior plane block with 0.375% ropivacaine. The primary outcome was the incidence of any pain at rest at 6 months postoperatively. Secondary outcomes included pain intensity and location at rest and with movement at 2 h, 24 h, 1 month, 3 months and 6 months postoperatively. RESULTS In total, 100 patients were enrolled and allocated randomly. For the primary outcome by intention-to-treat analysis, nine (18%) patients allocated to the intervention group reported post-mastectomy pain at rest at 6 months postoperatively compared with 19 (38%) allocated to the control group (OR 0.36, 95%CI 0.13-0.98, p = 0.044). Per-protocol analysis, not including three cases of protocol violation, showed no difference between groups for the same comparison. Pain scores were very low in both groups at 6 months postoperatively, and no patient was still using analgesics. There were no differences in acute pain scores or other secondary outcomes. DISCUSSION The addition of interpectoral plane block to superficial serratus anterior plane block may reduce the incidence of rest pain at 6 months post-mastectomy. Other factors influence chronic postsurgical pain development and deserve further study.