Axillary Brachial Plexus Block - ARiRA Pro Tips
Indications: The axillary brachial plexus block is a highly effective regional anaesthesia technique used for forearm, wrist, and hand procedures. It is commonly performed for hand and wrist surgeries, such as carpal tunnel release, tendon repairs, and metacarpal or phalangeal fracture fixation. It is also frequently used in soft tissue procedures, including wound debridement, abscess drainage, and skin grafting. In trauma surgery, the block provides excellent anaesthesia for forearm fractures and dislocations, making it a preferred choice in outpatient and same-day surgeries where long-lasting analgesia is required for rapid postoperative recovery.
Anatomy: The axillary brachial plexus block targets the terminal branches of the brachial plexus in the axilla. The median, ulnar, and radial nerves surround the axillary artery in a perivascular arrangement, requiring uniform local anaesthetic spread to ensure complete blockade. The musculocutaneous nerve, however, lies separately within the coracobrachialis muscle and requires a separate injection to provide complete sensory and motor blockade to the lateral forearm. On ultrasound, the nerves appear hypoechoic, round structures encircling the axillary artery, and precise needle placement with real-time guidance is key to achieving an effective block.
Patient Positioning: Position the patient supine, with the arm abducted to 90 degrees and externally rotated to provide optimal access to the axilla. A slight shoulder lift may improve ergonomics and facilitate a more comfortable needle approach. The ultrasound probe should be positioned transversely in the axilla, directly over the axillary artery, to ensure clear imaging of the nerve structures. Proper positioning enhances needle control, reduces patient discomfort, and optimises procedural success.
Ultrasound Technique: A high-frequency linear probe is used to visualise the axillary artery and its surrounding nerves. The median, ulnar, and radial nerves typically appear grouped around the artery, while the musculocutaneous nerve is often seen separately within the coracobrachialis muscle. Optimising depth and gain settings improves differentiation between nerves, vascular structures, and surrounding tissue planes.
Needle Insertion: The preferred approach is an in-plane lateral-to-medial technique, allowing continuous needle tip visualisation as it advances towards the target nerves. Hydrodissection with saline is recommended to enhance nerve differentiation and ensure safe needle advancement without excessive force. A separate injection is required within the coracobrachialis muscle to block the musculocutaneous nerve, preventing incomplete analgesia. A steady hand and careful needle trajectory are essential to achieving an effective and safe block.
Injection Volume: Typically, 20–30 mL of local anaesthetic is required for a successful block, ensuring adequate spread around all terminal branches of the brachial plexus. Lower volumes, in the range of 15–20 mL, may be effective when using perineural catheters or when adjunct techniques are applied to prolong the duration of anaesthesia.
Preventing Incomplete Block: To ensure complete sensory and motor blockade, it is essential to confirm that all nerves receive adequate anaesthetic coverage. The musculocutaneous nerve is often missed if a separate injection within the coracobrachialis muscle is not performed. Ensuring proper ultrasound imaging, correct hydrodissection, and slow injection techniques can significantly improve the effectiveness of the block and reduce the need for supplemental injections.
Minimising Vascular Puncture Risk: Since the axillary artery is a key anatomical landmark in this block, vascular puncture is a potential complication. To minimise risk, always use real-time ultrasound guidance, aspirate before injecting, and inject in small increments (3–5 mL) to monitor for any signs of intravascular placement. Utilising Doppler ultrasound mode can help identify vascular structures and avoid accidental punctures.
Reducing LAST (Local Anaesthetic Systemic Toxicity) Risk: LAST can be a serious complication when performing peripheral nerve blocks, particularly in highly vascular regions such as the axilla. To mitigate this risk, aspirate before each injection, inject slowly in small aliquots, and continuously observe for signs of toxicity. Using ultrasound guidance to confirm proper needle placement can help ensure accurate local anaesthetic delivery, reducing systemic absorption and enhancing patient safety.
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Axillary Brachial Plexus Block – FAQs
Q: What is the axillary brachial plexus block?
A: It is a regional anaesthesia technique that provides effective pain relief and surgical anaesthesia for procedures of the forearm, wrist, and hand by blocking the terminal branches of the brachial plexus in the axilla.
Q: How does the axillary brachial plexus block compare to the supraclavicular and infraclavicular blocks?
A: The axillary nerve block is safer than the supraclavicular block as it eliminates the risk of pneumothorax and phrenic nerve involvement. Unlike the infraclavicular block, which requires deeper needle insertion, the axillary approach is superficial, safer, and well-suited for outpatient surgery.
Q: What local anaesthetic is used for an axillary nerve block?
A: The choice depends on the desired block duration:
Short procedures (2–3 hours): Lidocaine.
Longer analgesia (8–18 hours): Ropivacaine or Bupivacaine.
Q: How can I ensure a complete nerve block?
A: Always confirm nerve coverage by injecting around the axillary artery for the median, radial, and ulnar nerves; and separately blocking the musculocutaneous nerve within the coracobrachialis muscle.
Q: Can this block be used for outpatient hand surgery?
A: Yes, the axillary brachial plexus block is one of the most common regional anaesthesia techniques used for day-case hand and wrist surgery, reducing the need for general anaesthesia.
Q: How can I minimise vascular puncture risk?
A: Use real-time ultrasound guidance, identify the axillary artery clearly, and aspirate before injecting. Doppler mode can help detect nearby vessels.
Q: How do I differentiate the nerves from surrounding structures?
A: The median, radial, and ulnar nerves appear as round, hypoechoic structures around the axillary artery, while the musculocutaneous nerve is separate in the coracobrachialis muscle. Hydrodissection improves visibility.
Q: What is the best way to learn ultrasound-guided nerve blocks?
A: The best way to master regional anaesthesia is through hands-on practice and structured training. Join the ARiRA Regional Anaesthesia Course and Elevate Your Expertise!
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Disclaimer: This content has been specifically tailored for healthcare professionals and is intended for educational purposes only. It provides guidance on optimising safety and efficacy in axillary brachial plexus block procedures but should not replace clinical judgment, institutional protocols, or professional training. Practitioners must always assess individual patient needs, adhere to local guidelines and regulatory requirements, and ensure they have the appropriate training and competency before performing any regional anaesthesia procedure.