How does a subpectoral plexus block differ from a Pectoral (PECS) block?

From the Guidelines

The subpectoral plexus block differs from the PECS block primarily in its target area and the nerves affected, with the subpectoral block targeting the brachial plexus branches within the subpectoral space and the PECS block targeting the lateral and medial pectoral nerves, intercostobrachial nerve, and long thoracic nerve. A subpectoral plexus block targets the brachial plexus branches within the subpectoral space, including the lateral pectoral, medial pectoral, and long thoracic nerves, as described in the context of breast surgery analgesia 1. It's performed by injecting local anesthetic deep to the pectoralis major muscle, near its insertion on the humerus. In contrast, the PECS block consists of two injections:

• PECS I: Between pectoralis major and minor muscles
• PECS II: Between pectoralis minor and serratus anterior muscles The PECS block primarily targets the lateral and medial pectoral nerves, intercostobrachial nerve, and long thoracic nerve, and has been shown to be effective in reducing pain and opioid consumption in breast surgery patients 1. For a subpectoral block, typically 20-30 mL of local anesthetic (e.g., 0.25% bupivacaine or 0.5% ropivacaine) is used, whereas for PECS, 10-20 mL is used for PECS I and an additional 20 mL for PECS II. The subpectoral block may provide more extensive analgesia to the chest wall and axilla, while PECS blocks are often used for breast surgery and axillary procedures, with studies showing similar results on pain relief and analgesia consumption between PECS and paravertebral blocks 1. Both blocks are typically performed under ultrasound guidance for accuracy and safety, as described in the context of paravertebral injections or catheter positioning 1. The choice between them depends on the specific surgical site and the desired extent of analgesia, with the goal of minimizing morbidity, mortality, and improving quality of life for patients undergoing breast surgery. Some studies have compared the efficacy of different blocks, including the erector spinae plane block, serratus plane block, and transversus thoracic muscle plane block, but the PECS block remains a commonly used and effective option for breast surgery analgesia 1. Overall, the subpectoral plexus block and PECS block are two distinct regional anesthesia techniques that can be used to provide effective pain management for patients undergoing breast surgery, with the choice between them depending on the specific clinical context and patient needs.

From the Research

Differences between Subpectoral Plexus Block and Pectoral (PECS) Block

• The subpectoral plexus block targets the nerves innervating the pectoral muscles, which are not affected by a multilevel thoracic paravertebral block alone 2.
• The PECS block, on the other hand, targets the nerves in the plane between the pectoralis major and minor muscles (PECS I) or between the pectoralis minor and serratus anterior muscle (PECS II) 3, 4.
• The subpectoral plexus block is performed by injecting local anesthetic near the origin of the thoracoacromial artery in the pectoserratus plane and between the two pectoral muscles (interpectoral plane) 2.
• In contrast, the PECS block is performed by injecting local anesthetic in the plane between the pectoralis major and minor muscles or between the pectoralis minor and serratus anterior muscle 3, 4.
• The subpectoral plexus block has been shown to enhance surgical anesthesia produced by a multilevel thoracic paravertebral block for primary breast cancer surgery 2.
• The PECS block has been shown to reduce intraoperative and postoperative opioid consumption, decrease the incidence of nausea and vomiting, and lead to overall patient satisfaction in terms of lower pain scores compared to systemic analgesia 3.

Similarities and Variations

• Both blocks are ultrasound-guided and target the fascial planes around the pectoral muscles 2, 3, 4.
• The PECS block has been refined and consolidated into a single thoracic fascial plane block, the SAP block, which shares the same mechanism of action as the PECS/serratus blocks 5.
• The serratus anterior plane block, a variation of the PECS block, has been shown to reduce pain scores and opioid consumption compared to systemic analgesia alone in cardiothoracic surgery and trauma 6.