Impact of Supra-Serratus versus Sub-Serratus Variations of Serratus Anterior Plane Block for Postoperative Analgesia and Quality of Recovery After Modified Radical Mastectomy: A Randomized Controlled Trial

Background and Aims: This study aimed to investigate the difference in postoperative analgesia and quality of recovery between the supra-serratus and sub-serratus approaches to serratus anterior plane block (SAPB) in women undergoing modified radical mastectomy for breast cancer surgery.
Methods: Seventy-nine (79) female patients scheduled for elective unilateral modified radical mastectomy were recruited to randomly receive superficial (supra-serratus) or deep (Sub-serratus) SAPB. The primary outcome was change in post-operative Numeric Rating Scale (NRS) Pain Scores over 24 hours. Secondary Outcomes were postoperative quality-of-recovery scores as assessed by the global quality-of-recovery-40 (QoR-40) questionnaire, total postoperative analgesic consumption, and time to first rescue analgesic.
Results: Sub-serratus block recipients experienced lower postoperative NRS pain scores, required less rescue analgesia, and reported higher global quality of recovery scores at the 24-hour postoperative period (183.54±6.33 vs. 170.29±7.01; p=0.003). Operators recorded poorer visualization and /or incomplete hydrodissection and linear spread of the local anaesthetic in patients receiving supra-serratus SAPB, especially with prior chest radiation exposure and with a body mass index of >30.
Conclusion: Sub-serratus variation of serratus anterior plane block is a more effective alternative to the supra-serratus approach in women undergoing MRM surgery in terms of superior block performance characteristics, lower postoperative pain scores, and better quality of recovery. Further large-scale trials are required to validate the benefits of this approach of SAPB, especially in obese breast surgical candidates and those presenting for MRM after chest wall radiation exposure.