Please confirm that an ethics committee approval has been applied for or granted: Not relevant

Background and Aims The Serratus Posterior Superior Muscle originates from C7-T2 ( sometimes T3) spinous processes, progressing obliquely and inserting on the lateral of the second to fifth ribs’ angles. SPSM differs anatomically from the trapezius, rhomboid major and minor muscles because is the only muscle that originates from the spinous process and extends deeply into the scapula. Due to this structure, it may theorically be advantageous for local anesthetic diffusion to dorsal ramus and lateral cutaneous branches of intercostal nerve at C3-T7 levels. The aim of this prospective randomized study is to evaluate the postoperative analgesic effectiveness of SPSIP and SAP in patients undergoing breast surgery.

Methods In this study 10 patients were analyzed. Patients undergoing breast surgery, specifically superior-external quadrantectomy, were divided into two groups before the operation. Group SPSIP ( n= 4) with 20 ml 0,5% ropivacaine under ultrasound guided. Group SAP ( n=6) received 20 ml of 0,5% ropivacaine under ultrasound guidance. Oppioid and FANS consumed, VAS scale were recorded at 2, 6, 12 and 24 hours. PONV was recorded in the postoperatory time

Results Total Opioid consumption in the first 24 hours postoperatively was significant lower in both group. The mean VAS score was 0.6 ( SD =0.8), indicating a very low level of pain in the first 24 hours post-operatively. The average length of hospital stay was one day for all patients.

Conclusions In the postoperative period following superior external quadrantectomy, both the SPSIP block and the SAP block, resulted in low VAS scales within the first 24 hours.