Axillary block

Know the landmarks, what you go through, what can go wrong, and the treatment and response for any block.

Brachial Plexus runs deep to the clavicle and superior to the 1st rib.

Remember, the nerves in the body usually run with vessels, which are used as landmarks.

Axillary Block

The axillary block is used for surgery on the hand and forearm but can also be used for elbow surgeries

Risk of missing the musculocutaneous branch

Any patient who is unable to abduct more than 45 degrees at the shoulder is not an appropriate candidate for the axillary block

The axillary block targets four terminal branches of the brachial plexus

Brachial Plexus

• R - roots
• T - trunks
• D - divisions
• C - cords
• B - branches

The plexus divides into five main terminal branches

• Median nerve - middle finger flexion                   
• Radial nerve - thumb abduction
• Ulnar nerve -little finger flexion, 4th and 5th finger movement             
• Musculocutaneous nerve - need to see biceps movement with blockade
• Axillary – deltoid muscle

Block Placement

Connect the patient to the pulse-ox opposite arm, EKG, and O₂ N/C. Perform the BP measurement while the patient is supine, arm flexed 90 degrees, and lying overhead.

Equipment

Gloves, Betadine, towels for some blocks, sterile insulated short bevel needle, nerve stimulator, sedation (Versed and Fentanyl), LA (with epinephrine to evaluate for intravascular injection), local anesthetics for skin, skin marker and ruler, competent assistant

May use Naropin 0.5% - 60 mL = 300 mg. It may last 4-6 hrs, with epi 8-12 hrs.

Max dose 3 mg/kg

Monitor with one EKG pad on the patient from the stimulator. Start with 1.2 mA and go down to 0.5 mA. Ensures appropriate proximity to the nerve. If you are below 0.3 and still get stimulation, you may be intraneural and don't want to inject here

Chart stimulation threshold

Continuous aspiration when the needle in the tissue

Technique

Transarterial

Locate the axillary artery, insert the needle, and aspirate until bright, red blood is obtained

The needle is then advanced or withdrawn until there is no blood aspiration

Usually, inject both posteriorly, anteriorly, or both.  40-60 mL, 1/2 posterior, 1/2 anterior - this varies

Nerve Stimulator

The axillary artery is pinned parallel to the fingers. The median nerve lies superior to the pulse, the ulnar nerve lies inferior, and the radial nerve is inferior/posterior to the pulse. The musculocutaneous nerve is separate and deep within the coracobrachialis muscle, which is superior and at risk of being missed.

Complications

This is rare due to the distance between neuraxial structures and the lung

Systemic toxicity (tingling, perioral numbness, metallic taste)

Postoperative neuropathy