Extra Topic 4.4 -- Axillary Block

Question 1

How would you evaluate his hypertension?

(A 22-year-old male presents for ORIF of the wrist. His blood pressure is 164/92 mmHg.)

Answer 1

In order to further evaluate his hypertension I would:

1. perform a focused history and physical to identify the cause of his hypertension, additional cardiovascular risk factors, and any end-organ damage (i.e. left ventricular hypertrophy or a strain pattern on ECG);
2. review his current therapy;
3. obtain an ECG, electrolyte panel, blood urea nitrogen, and creatinine to further evaluate end-organ damage and identify metabolic derangements resulting from medications used in the treatment of hypertension; and,
4. if the cause of his hypertension were unknown, attempt to identify potential causes of hypertension in a young adult, such as –
   
   • pheochromocytoma,
   • hyperthyroidism,
   • coarctation of the aorta, and
   • illicit drug use (cocaine, amphetamines, steroids, etc.)

Question 2

What is your anesthetic plan?

(A 22-year-old male presents for ORIF of the wrist. His blood pressure is 164/92 mmHg.)

Answer 2

If there were no contraindications, my plan would be to perform an axillary block, which is easy to perform, provides complete anesthesia at the wrist, and has a low complication rate.

As with any regional block, I would discuss the risks with the patient, including the possibility of sedation and conversion to a general anesthetic, should the block be inadequate.

Question 3

How would you perform an axillary block?

(A 22-year-old male presents for ORIF of the wrist. His blood pressure is 164/92 mmHg.)

Answer 3

I would place the patient in the supine position with the arm abducted and the elbow flexed at 90 degrees.

Next, I would prep and drape the axillary area in a sterile fashion, use ultrasound to identify the axillary artery and fascial sheath, insert a 22 gauge short bevel needle into the nerve sheath under ultrasound guidance, aspirate to ensure extravascular needle placement, and inject 15-20cc of local anesthetic.

I would then identify the musculocutaneous nerve within the coracobrachialis muscle and inject 5cc of local anesthetic next to the nerve.

If a tourniquet was required for the surgery, I would perform a subcutaneous field block just distal to the axilla to block the medial brachial cutaneous and intercostobrachial nerves.

Question 4

What are the complications associated with an axillary block?

(A 22-year-old male presents for ORIF of the wrist. His blood pressure is 164/92 mmHg.)

Answer 4

While the axillary approach to a brachial plexus block is associated with a very low complication rate, there are potential complications, including –

• intravascular injection,
• hematoma,
• infection, and
• block failure.

Question 5

Which nerve is most commonly missed?

(A 22-year-old male presents for ORIF of the wrist. His blood pressure is 164/92 mmHg.)

Answer 5

The musculocutaneous nerve, which provides motor innervation to the biceps muscle and sensory innervation to the lateral aspect of the forearm, has already left the sheath at the level of the axilla and, subsequently, is the most commonly missed.

Adequate blockade of the musculocutaneous nerve is achieved by injecting 5cc of local anesthetic into the coracobrachialis muscle.