Brachial Plexus Block

Anatomy of the Brachial Plexus

• Lateral cord → musculocutaneous nerve + lateral head of median nerve
• Medial cord → ulnar nerve + medial head of median nerve + medial cutaneous nerves of arm and forearm
• Posterior cord → axillary nerve + radial nerve

(FIG. 42.12 - Miller's Anesthesia 10e: A) Cervical root dermatomes, B) Peripheral nerve cutaneous distribution)

Approaches - Overview

(FIGURE 69.4 - Campbell's Operative Orthopaedics 2026: A. Interscalene, B. Supraclavicular, C. Infraclavicular single injection, D. Axillary multiple injections)

1. Interscalene Block (ISB)

• Shoulder surgery (the preferred technique)
• Proximal humerus, clavicle, and acromioclavicular joint surgery
• Elbow surgery (with supplementation)

• Patient supine, head turned away from side to be blocked
• High-frequency linear probe placed at the supraclavicular fossa, then traced up the neck until trunks appear as hypoechoic structures between anterior and middle scalene muscles - the classic "stoplight" sign (three stacked circles)
• Needle inserted in-plane or out-of-plane; local anesthetic deposited within the periplexus space

Phrenic-sparing alternatives: The superior trunk block and anterior suprascapular nerve block target the suprascapular nerve (providing ~70% of shoulder joint innervation) with less phrenic nerve involvement. A low-dose (15 mL) superior trunk block shows noninferior pain scores with less hemidiaphragmatic paralysis vs. standard ISB. - Miller's Anesthesia 10e

2. Supraclavicular Block

• Elbow, forearm, and hand surgery
• Considered the spinal of the upper extremity for rapid, reliable coverage

• Patient supine, head turned away, arm adducted
• High-frequency linear transducer just proximal to supraclavicular fossa
• Plexus appears as a cluster of hypoechoic circles lateral to the subclavian artery, above the first rib
• Needle advanced in-plane, lateral to medial
• Volume: 15-30 mL (higher volumes risk ischemic compression in this compact space)
• The first rib acts as a medial barrier protecting from reaching the pleural dome

• Pneumothorax: 0.5-6% (risk persists even under ultrasound)
• Phrenic nerve block: 40-60%
• Horner syndrome
• Avoid in uncooperative patients or those who cannot tolerate any respiratory compromise

3. Infraclavicular Block

• Elbow, forearm, wrist, and hand surgery
• Preferred approach for catheter placement - stable location, extra muscle/fascial layers hold the catheter securely, arm manipulation not required

• Preferred: lateral sagittal (paracoracoid) approach - probe in parasagittal plane medial to the coracoid process
• Axillary artery visualized in short-axis, deep to pectoralis major and minor
• Needle placed posterior to the axillary artery (single injection)
• 30-40 mL posterior to the axillary artery provides complete plexus block
• Cords do NOT need to be directly visualized for success
• Costoclavicular approach (alternative): cords clustered lateral to first part of axillary artery; faster onset but higher pleural puncture risk

• Deep block - steep needle angle makes tip visibility challenging
• Vascular puncture (accessory axillary vein lies adjacent to the lateral cord)
• No significant phrenic nerve block
• No arm positioning required (advantage over axillary)

4. Axillary Block

• Forearm, wrist, and hand surgery
• Similar coverage to infraclavicular

• Brachial plexus block at the cord/terminal nerve level provides excellent anesthesia at or distal to the elbow; the upper arm and shoulder are NOT covered
• The intercostobrachial nerve (T2) is spared with all brachial plexus approaches - requires separate subcutaneous infiltration for medial arm tourniquet analgesia
• Nerves that branch proximal to the injection site are usually spared: axillary nerve, musculocutaneous nerve, medial brachial cutaneous nerve
• The musculocutaneous nerve (lateral forearm) can be independently blocked by infiltrating the coracobrachialis muscle

• Arm abducted 90 degrees (may be difficult with trauma or contractures)
• Ultrasound-guided multiple injection: identify each terminal nerve around axillary artery
• Multiple injection > single injection for reliability

• Infection in the axilla
• Axillary lymphadenopathy
• Axillary malignancy

• Dysesthesias and "brachialgia" post-block (inform the patient)
• Lower complication rate vs. proximal approaches (no pneumothorax, no phrenic block)

Localization Techniques Compared

Local Anesthetic Selection

• Both short- and long-acting agents can be used
• Choice depends on agent, technique, and clinical preference
• For sustained analgesia: continuous catheter (infraclavicular preferred for catheter placement)
• Multiple-injection technique is more effective than single or double injection
• High volumes in compact spaces (supraclavicular) carry risk of ischemic neural compression

Approach Selection Summary

• Miller's Anesthesia, 10e, Chapter 42 - Upper Extremity Regional Anesthesia
• Campbell's Operative Orthopaedics, 15e (2026) - Chapter 69: Brachial Plexus Blocks
• Morgan & Mikhail's Clinical Anesthesiology, 7e - Chapter 46
• Barash's Clinical Anesthesia, 9e - Chapter 42