A randomised controlled trial of pectoral nerve-2 (PECS 2) block vs. serratus plane block for chronic pain after mastectomy.

Thoracic interfascial plane blocks are effective for post-mastectomy acute analgesia. However, their effects on chronic pain are uncertain. We randomly allocated 80 women equally to pectoral nerve-2 (PECS 2) block or serratus plane block. The pectoral nerve-2 block reduced the rate of moderate or severe chronic pain from 13/40 (33%) with the serratus plane block to 4/40 (10%), p = 0.03, adjusted odds ratio (95%CI) 0.23 (0.07-0.80), p = 0.02. The rates of pain-free women at six postoperative months were indeterminate, 10/40 (25%) after serratus plane block vs. 19/40 (48%) after pectoral nerve-2 block, p = 0.06, adjusted odds ratio (95%CI) 2.9 (1.1-7.5), p = 0.03. Health-related quality of life at six postoperative months was similar after serratus plane and pectoral nerve-2 blocks, mean (SD) EQ-5D-3L scores 0.87 (0.15) vs. 0.91 (0.14), respectively, p = 0.21. The pectoral nerve-2 block reduced median (IQR [range]) morphine consumption in the first 24 postoperative hours from 6 (3-9 [1-25]) mg to 4 (2-7 [0-37]) mg, p = 0.04. However, acute pain scores after serratus plane and pectoral nerve-2 blocks were similar, median (IQR [range]) 23 (11-35 [0-70]) mm vs. 18 (11-27 [0-61]) mm, respectively, p = 0.44. Pectoral nerve-2 block reduced chronic pain 6 months after mastectomy compared with serratus plane block.