Comparing the quality of analgesia with ultrasound-guided pectoral nerve block and serratus anterior plane block II in patients undergoing modified radical mastectomy: a randomised clinical trial

Background: Despite the recent use of serratus anterior plane (SAP) and pectoral nerve (PECS) blocks for pain management following breast surgery, there are insufficient data comparing their analgesic benefits. This study aimed to compare the quality of analgesia for PECS and SAP blocks in patients having modified radical mastectomy (MRM). Methods: This trial enrolled 50 adult female patients scheduled for MRM under anaesthesia. Patients were randomly allocated to two groups. After induction of anaesthesia, 25 patients received US-guided PECS II block, and 25 patients received US-guided SAP block. The primary outcome was the time to first analgesic request. Secondary outcomes included the total analgesic consumption and postoperative pain during the first 24 hours as well as the total time to perform the block, surgeon satisfaction, haemodynamic parameters, and postoperative nausea and vomiting. Results: Time to first analgesic request was significantly longer in the SAP group than in the PECS II block group (95% CI: 90.2–574.5, P = 0.009). The SAP block significantly lowered the total analgesics consumption, the 24 hours patient’s need for analgesia, and the VAS scores immediately, as well as at 2, 8, 20, 22, and 24 hours postoperatively (P < 0.005). Although it required a longer preparation time than PECS II block, the SAP block had comparable surgeons’ satisfaction, haemodynamic parameters, and postoperative nausea and vomiting to PECS II block. Conclusions: Following MRM, US-guided SAP block provided a delayed time to first rescue analgesia with better acute pain control and lower total analgesic consumption compared to the PECS II block.