Explain me brachial plexus block with anatomy as anesthesia pg

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Brachial Plexus Block - Complete Guide for Anesthesia PG

1. Anatomy of the Brachial Plexus

The brachial plexus is formed by the ventral rami (anterior primary divisions) of C5, C6, C7, C8, and T1. Minor contributions from C4 and T2 may occur. The organization follows the mnemonic RTDCB: Roots → Trunks → Divisions → Cords → Branches (terminal nerves).

Organization

Level	Components	Location
Roots	C5, C6, C7, C8, T1	Exit intervertebral foramina
Trunks	Superior (C5+C6), Middle (C7), Inferior (C8+T1)	Between anterior & middle scalene muscles
Divisions	Anterior & posterior from each trunk (6 total)	Over lateral border of 1st rib, under clavicle
Cords	Lateral, Medial, Posterior	Named relative to axillary artery; below clavicle
Terminal nerves	Median, Ulnar, Radial, Musculocutaneous, Axillary	Lateral border of pectoralis minor

Cord-to-Terminal Nerve Formation

Lateral cord → lateral head of median nerve + musculocutaneous nerve
Medial cord → medial head of median nerve + ulnar nerve + medial brachial cutaneous + medial antebrachial cutaneous nerves
Posterior cord → axillary nerve + radial nerve

Brachial plexus organization - roots, trunks, divisions, cords and interscalene region

Brachial plexus organization showing roots C4-T1, upper/middle/lower trunks, cords, and the interscalene location - Morgan & Mikhail's Clinical Anesthesiology, 7e

Pre-terminal Branches (Important - often missed)

Dorsal scapular nerve (C5) - rhomboids
Long thoracic nerve (C5, C6, C7) - serratus anterior
Suprascapular nerve (C5, C6) - supraspinatus, infraspinatus, glenohumeral joint - branches from upper trunk, must be blocked for complete shoulder analgesia
Nerve to subclavius (C5, C6)

Nerve Sensory Distribution

Sensory distribution of brachial plexus terminal nerves - anterior and posterior views of upper limb

Cutaneous nerve distribution of the upper limb - anterior (palmar) and posterior (dorsal) views - Morgan & Mikhail's Clinical Anesthesiology, 7e

2. Approaches to Brachial Plexus Block

The key principle is: where you inject determines what you block. Proximal blocks intercept roots/trunks (shoulder and above). Distal blocks intercept cords/terminal nerves (elbow and below).

Approach	Anatomical Level Targeted	Surgical Indication
Interscalene	Roots / upper & middle trunks	Shoulder, proximal humerus
Supraclavicular	Distal trunks / proximal divisions	Elbow, forearm, hand ("spinal of the arm")
Infraclavicular	Cords	Elbow, forearm, hand; best for catheters
Axillary	Terminal nerves	Hand, wrist, forearm distal to elbow

3. Interscalene Block

Anatomy

The brachial plexus trunks lie between the anterior scalene and middle scalene muscles in the neck, visualized at the C6 level. The phrenic nerve (C3-C5) lies directly on the anterior scalene muscle just medial to the interscalene groove.

Indication

Shoulder surgery, proximal humerus fractures, AC joint procedures. Not suitable for hand/wrist surgery because C8-T1 (inferior trunk, ulnar distribution) is frequently spared.

US-Guided Technique

Patient supine, head turned 30-45° away from the side to be blocked
High-frequency linear probe placed at the level of the cricoid cartilage (C6)
Trace the plexus cephalad from a supraclavicular view until the trunks appear as hypoechoic structures between the scalene muscles - the "stoplight" sign (three trunks stacked vertically)
In-plane or out-of-plane needle approach; out-of-plane avoids the long thoracic and dorsal scapular nerves inside the middle scalene
Local anesthetic volume: 10-20 mL surrounds the trunks

Key Point for Shoulder Coverage

The supraclavicular nerve (C3-C4, from cervical plexus) covers the "cape" area of the shoulder. A separate cervical plexus block or subcutaneous infiltration along the clavicle is needed for complete shoulder anesthesia.

Complications

Ipsilateral phrenic nerve block - near 100% incidence with conventional volumes; causes hemidiaphragmatic paralysis. Contraindicated in contralateral phrenic nerve palsy, severe COPD/restrictive disease (FEV1 or FVC <50%)
Recurrent laryngeal nerve block (hoarseness)
Horner syndrome (ptosis, miosis, anhidrosis)
Cervical sympathetic chain block
Vertebral artery injection (risk of CNS toxicity)
Intrathecal/epidural injection
Spinal cord injury with high-volume injection

4. Supraclavicular Block

Anatomy

At the lateral border of the first rib, all six divisions of the brachial plexus are compact in a space <1 cm, making this the most efficient location for complete upper extremity anesthesia. The subclavian artery lies medial/deep, the first rib is deep (bony backstop), and the pleura is just beyond the rib.

Indication

Operations on elbow, forearm, and hand. Sometimes called the "spinal of the arm" due to rapid onset and dense block.

Not ideal for: shoulder surgery (suprascapular nerve, which is a proximal branch of upper trunk, is not reliably blocked).

US-Guided Technique

Patient supine, head turned 30° away
High-frequency linear probe placed in the supraclavicular fossa, angled slightly toward thorax
Subclavian artery identified as pulsatile structure; brachial plexus appears as "cluster of grapes" - multiple hypoechoic nodules, just superficial and posterolateral to the artery
First rib is a hyperechoic line deep to the artery; pleura lies just beyond and moves with respiration
Needle inserted posterolateral in-plane toward subclavian artery; aim for the "corner pocket" between artery, plexus, and first rib - this ensures inferior trunk (ulnar nerve distribution) is adequately blocked
Local anesthetic: 20-30 mL, injected in multiple locations to encircle plexus

Supraclavicular block ultrasound - brachial plexus divisions around subclavian artery, first rib and pleura

Supraclavicular US showing subclavian artery (red), divisions of the brachial plexus (yellow - SA/SP/MA/MP/IA/IP = superior/middle/inferior anterior and posterior divisions), first rib, and pleura - Morgan & Mikhail's, 7e

Complications

Pneumothorax (most feared; risk ~0.5-1%, reduced but not eliminated by US)
Phrenic nerve palsy (~50% incidence - less than interscalene but still significant)
Subclavian artery puncture
Horner syndrome
Ulnar sparing (if "corner pocket" injection is missed)

5. Infraclavicular Block

Anatomy

Below the clavicle, the brachial plexus is now organized as three cords arranged around the axillary artery:

Lateral cord - lateral/cephalad to artery
Medial cord - medial/caudad to artery
Posterior cord - posterior to artery

All three cords lie deep to the pectoralis major and pectoralis minor muscles. The subclavian artery becomes the axillary artery at the lateral border of the first rib.

Indication

Surgery at or distal to the elbow. Preferred approach for perineural catheter placement (superior to supraclavicular and axillary catheters due to muscle and fascial layers securing it).

US-Guided Technique

Patient supine; arm abducted 90° (dramatically improves visualization)
High-frequency linear or small curvilinear probe placed parasagittal, 2 cm medial and 2 cm caudad to coracoid process
Axillary artery and vein seen in cross-section; cords appear as hyperechoic bundles:
- Lateral cord - cephalad to artery
- Medial cord - caudad to artery
- Posterior cord - posterior (deep) to artery
A long (10-cm) needle inserted 1-3 cm cephalad to probe tip, angled steeply
Optimal injection: between artery and posterior cord ("U" of local anesthetic wrapping around artery); a single 30-mL injection at this location is equivalent to individual cord injections
Catheter tip placed posterior to artery for continuous infusion

Complications

Vascular puncture (axillary artery or vein)
Pneumothorax (less common than supraclavicular)
Hematoma
Contraindicated: ipsilateral subclavian vascular catheter, transvenous pacemaker

6. Axillary Block

Anatomy

At the lateral border of pectoralis minor, the cords have divided into terminal branches surrounding the axillary artery in fascial compartments:

Median nerve - anterior/medial to artery
Radial nerve - posterior to artery
Ulnar nerve - medial to artery
Musculocutaneous nerve - already departed and lies within the coracobrachialis muscle (must be separately targeted)
Axillary nerve - already branched proximally (not blocked by axillary approach)
Medial brachial & antebrachial cutaneous nerves - branch proximally (spared)

Because the nerves are separated by fascial compartments at this level, multiple injections are usually required.

Indication

Surgery on hand, wrist, and forearm distal to elbow. Most superficial and safe approach.

Not suitable for: arm tourniquet at the upper arm (intercostobrachial nerve, T2, is spared and must be blocked separately with subcutaneous infiltration along the axilla).

US-Guided Technique

Patient supine, arm abducted 90°, elbow flexed, forearm externally rotated (supinated)
High-frequency linear probe placed in axilla, perpendicular to arm
Axillary artery pulsates in center; veins are compressible; nerves are hyperechoic
Individual injections around each nerve (5-10 mL per nerve)
Musculocutaneous nerve located as oval hyperechoic structure within coracobrachialis muscle - requires separate injection
Total volume: 25-40 mL

Complications

Axillary artery/vein puncture (most common; hematoma formation)
Nerve injury
Local anesthetic systemic toxicity (LAST) - highly vascular area

7. Phrenic Nerve-Sparing Approaches for Shoulder Surgery

Patients with significant pulmonary disease cannot tolerate interscalene block (phrenic nerve palsy). Alternatives:

Superior trunk block - targets C5-C6 at the level where suprascapular nerve branches; 5-15 mL deep to omohyoid muscle; significantly less phrenic nerve involvement
Anterior suprascapular nerve block - blocks the suprascapular nerve proximal to suprascapular notch; combined with infraclavicular block for complete shoulder coverage

8. Local Anesthetics Used

Drug	Concentration	Duration	Onset
Ropivacaine	0.375-0.5% (surgical), 0.2% (analgesia)	8-12 h	Moderate
Bupivacaine	0.25-0.5%	8-16 h	Moderate
Lidocaine	1-1.5% (±epi)	2-4 h	Rapid
Mepivacaine	1-1.5%	4-6 h	Rapid

Adding epinephrine (1:200,000) prolongs duration and serves as an intravascular injection marker. Dexamethasone 4-8 mg (IV or perineural) reliably extends block duration by 6-8 hours.

9. Contraindications (General)

Patient refusal
Local infection at injection site
Severe coagulopathy (relative; varies by approach depth)
True local anesthetic allergy
Pre-existing severe neurological deficit (relative)
Bilateral blocks (combined phrenic nerve palsy risk)

10. Complications Overview

Complication	Most Common Approach
Phrenic nerve palsy	Interscalene (>95%), Supraclavicular (~50%)
Pneumothorax	Supraclavicular > Infraclavicular
Horner syndrome	Interscalene, Supraclavicular
Recurrent laryngeal nerve	Interscalene
Vascular puncture	Axillary, Infraclavicular
LAST	All (especially axillary - high vascularity)
Nerve injury	All approaches
Spinal/epidural injection	Interscalene

Summary - "Which Block for Which Surgery?" (Exam Table)

Surgery	Best Approach	Why
Shoulder arthroplasty / RCR	Interscalene	Targets C5-C6 roots + upper trunk
Clavicle ORIF	Interscalene + cervical plexus	Supraclavicular nerve (C3-C4) supplementation needed
Shoulder (high-risk lung)	Superior trunk / suprascapular + infraclavicular	Phrenic-sparing
Elbow / forearm	Supraclavicular or infraclavicular	Dense block at division/cord level
Wrist / hand	Infraclavicular or axillary	Cord / terminal nerve level
Catheter for prolonged analgesia	Infraclavicular	Best catheter stability
Pediatric or obese arm	Axillary	Superficial, safe

Sources: Miller's Anesthesia 10e, Morgan & Mikhail's Clinical Anesthesiology 7e, Barash Clinical Anesthesia 9e

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Brachial Plexus Block Selection

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Contents of the PDF:

Brachial Plexus Anatomy Overview - Roots → Trunks → Divisions → Cords → Terminal nerves table with approach targeting at each level + cord-to-nerve formation box
Block Selection by Surgery - Color-coded by region (Shoulder / Upper Arm / Elbow-Forearm / Wrist-Hand) with preferred block, level targeted, LA volume, and key notes for each procedure
Approach Profiles at a Glance - All 4 approaches with US landmarks, ideal indications, spared nerves, complications, and catheter suitability
Local Anaesthetics & Adjuvants - Ropivacaine, bupivacaine, lidocaine, mepivacaine with concentrations, onset, duration; dexamethasone and dexmedetomidine adjuvants
Contraindications & Complications - Absolute vs. relative contraindications side-by-side; complication matrix by approach with risk highlighting
Quick Decision Algorithm - 6-step clinical decision flow from surgery site → block choice

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