Two-point deep serratus anterior plane block for modified radical mastectomy – A case series assessing axillary coverage using structured sensory mapping

Serratus anterior plane block (SAPB) provides chest wall analgesia in modified radical mastectomy (MRM) surgeries by targeting T2–T6 intercostal nerves, but conventional single-injection techniques show inconsistent T2 and axillary coverage, failing to reliably block the intercostobrachial nerve – a key contributor to postoperative axillary pain and postmastectomy pain syndrome. MRM patients experience significant axillary pain from dissection-related intercostobrachial nerve (ICBN) injury, necessitating multimodal analgesia that ensures reliable T2-axillary desensitisation. There is inadequate cephalad/axillary spread in standard SAPB, confirmed by prior studies showing <20% T2 blockade and variable ICBN involvement despite high local anaesthetic volumes. This prospective case series included 10 patients in whom ultrasound-guided deep two-point SAPB was administered with 20 mL of 0.375% ropivacaine at the 5 th rib midaxillary line and 10 mL at the 3 rd rib anterior axillary line. Sensory mapping via grid, cold/pin-prick Likert scores, and photography 30 min post-block showed reliable T2–T6 dermatomal desensitisation (70% success: composite score >4) confirmed by heat maps. It is concluded that two-point injection at 3 rd and 5 th rib enhances T2/ICBN blockade over single-level SAPB; nevertheless, larger randomised controlled trials are needed for opioid-sparing validation.