RISS vs ESP Block for Postoperative Analgesia After Mastectomy

Breast cancer is one of the most common types of cancer worldwide and represents a major public health concern (1). Treatment options depend on the stage and pathological characteristics of the disease and may include radiotherapy, neoadjuvant systemic therapies, breast-conserving surgery, and mastectomy (2).

Modified radical mastectomy (MRM) is associated with significant postoperative pain, which may arise from a combination of nociceptive and neuropathic mechanisms related to surgical trauma. Inadequately controlled postoperative pain may contribute to adverse outcomes, including cardiovascular and pulmonary complications and thromboembolic events. Furthermore, acute postoperative pain may interfere with functional recovery and may contribute to the development of persistent or chronic pain, thereby negatively affecting quality of life (3). Uncontrolled postoperative pain may also prolong hospital stay, increase the risk of complications, and increase healthcare costs. Therefore, effective postoperative pain management is an important component of perioperative care in patients undergoing breast surgery (4).

Opioids remain an important component of postoperative analgesia, while nonsteroidal anti-inflammatory drugs and other non-opioid analgesics are commonly used as adjunctive therapies. However, the potential systemic adverse effects associated with these medications have increased interest in regional anesthesia techniques. Neuraxial techniques, peripheral nerve blocks, and intravenous patient-controlled analgesia can provide effective postoperative analgesia while reducing opioid requirements and facilitating postoperative recovery. In particular, ultrasound-guided regional anesthesia techniques allow real-time visualization of anatomical structures and needle advancement, potentially improving the accuracy and safety of block administration and the quality of analgesia (5).

Regional anesthesia techniques may support early postoperative mobilization and contribute to enhanced recovery after surgery (ERAS) pathways. These techniques have been reported to contribute to reducing the risk of venous thromboembolism and pulmonary complications. Improved analgesia may also facilitate deep-breathing exercises and postoperative physiotherapy. Furthermore, regional anesthesia techniques may reduce opioid and antiemetic requirements, facilitate early mobilization after mastectomy, and potentially contribute to reducing chronic postmastectomy pain (6,7).

The erector spinae muscle group extends in a craniocaudal direction on both sides of the vertebral column and lies deep to the rhomboid major muscle in the thoracic region. In an erector spinae plane block (ESPB), local anesthetic is injected into the fascial plane between the transverse process and the erector spinae muscle (8). The local anesthetic may spread in a craniocaudal direction across multiple vertebral levels. ESPB has been used for the management of acute and chronic pain and for perioperative analgesia in various thoracic and abdominal surgical procedures (8).

The analgesic effect of ESPB is thought to result from the spread of local anesthetic to the dorsal and ventral rami of the thoracic spinal nerves. However, the extent and consistency of local anesthetic spread to the ventral rami may vary (9). ESPB has also been proposed to provide an effect on both somatic and visceral pain (9). When prolonged analgesia is required, a catheter can be placed in the erector spinae plane to allow continuous or intermittent administration of local anesthetic (10). Previous studies in patients undergoing breast surgery have demonstrated that ESPB may improve postoperative pain control and reduce opioid consumption, with analgesic efficacy potentially comparable to that of paravertebral block (11,12).

The rhomboid intercostal and subserratus plane (RISS) block is an ultrasound-guided fascial plane block first described by Elsharkawy and colleagues in 2018. It has been used for the management of thoracic and upper abdominal pain (13). In this technique, local anesthetic is administered into the fascial plane between the rhomboid and intercostal muscles and subsequently into the plane superficial to the serratus anterior muscle. The technique is intended to block the lateral cutaneous branches of the intercostal nerves at approximately the T3-T9 levels (13). Medial spread of local anesthetic may also affect the dorsal rami of the thoracic spinal nerves located deep to the erector spinae muscle (13).

In the present randomized controlled study, patients scheduled to undergo modified radical mastectomy and sentinel lymph node excision will be randomized to receive either an ultrasound-guided ESPB or an ultrasound-guided RISS block as part of their perioperative analgesic management.

The primary objective of this study is to compare the postoperative analgesic efficacy of ESPB and RISS block. Postoperative opioid consumption will be evaluated as the primary outcome. Secondary outcomes will include postoperative pain intensity, rescue analgesic requirements, and patient satisfaction.

The study hypothesis is that ultrasound-guided ESPB and RISS block provide comparable postoperative analgesia in patients undergoing modified radical mastectomy and sentinel lymph node excision, and that neither technique is superior to the other in terms of postoperative analgesic efficacy.