The axillary approach to the brachial plexus block is well known and widely practiced using the parasthesia, nerve stimulation and transarterial techniques. Adapting the approach to the use of ultrasound is intuitive because of the nature of the anatomy. The median, radial and ulnar nerves lie around the easily found axillary artery. The musculocutaneous nerve is usually fairly easy to find in the nearby coracobrachialis muscle.
The patient is supine with the target arm abducted, supinated and flexed at the elbow. The hand is place beside or behind the patient’s head and supported by a pillow.
After prepping, the probe is placed transversely against the upper, inner arm just below the axilla so that the beam will cross the suspected path of the axillary artery. The artery is identified by it’s resistance to collapse when pressure is placed on the probe. The vein(s) around the artery usually disappear when a moderate amount of pressure is placed on the probe.
Lateral to the artery (anatomically speaking, but towards the patient’s head in terms of the room) lies the median nerve. On the other side of the axillary artery (medial, anatomically) is the radial nerve. The ulnar nerve lies more medially.
The orientation of the nerves to the artery changes as they proceed distally, so the above description applies only at the level just below the axilla and and only in most people.