Axillary Block

Indications

The axillary technique is ideal for operatiaons of the hand, elbow, and some forearm operations (provided that they are not innervated by the lateral cutaneous nerve of the forearm)

Relevant Anatomy

Landmarks and Surrounding Structures

The most important landmark is the axillary artery, as the neurovascular bundle is oriented reliably around it – median nerve superiorly, ulnar nerve inferiorly, radial nerve posterior/lateral

Brachial Plexus Anatomy

The brachial plexus is thought to consist of C5-T1, although it may expand by one nerve in either direction (C4-T2). Essential to the anesthesiologist is an understanding of the trunks – upper, middle, and lower

Upper (C5-C6)
Middle (C7)
Lower (C8-T1)

Cutaneous Innervation

Axillary technique reliably blocks the axillary, median, and radial nerves (but not the axillary or musculocutaneous – they leave the brachial plexus at the level of the coracoid process)

Distributions Missed by the Axillary Technique

The axillary technique reliably blocks the ulnar, median, and radial nerves (but not the musculocutaneous and the intercostobrachial nerves which leave the brachial plexus at the level of the coracoid process).

Technique

Abduct the arm 90 degrees. Identify the axillary artery as proximally as possible, and trace its course. Press the artery into the humerus near the axillary skin crease, and inject a 4-5 cc of local anesthetic (will block the intercostobrachial nerve, potentially decreasing tourniquet pain). Traditional techniques include nerve stimulation as well as transarterial techniques (40-50 cc posterior to the artery). Ultrasound has a faster onset of sensory block but is no different in terms of motor block, time to readiness for surgery, or block success rate as compared to nerve stimulation techniques [Casati A et al. Anesthesiology 106: 896, 2007]. Adduction of the arm following the block appears to reduce onset time and prolong both the sensory and motor blockade [Ababou A et al. Anesth Analg 104: 980, 2007]. The musculocutaneous nerve can be blocked either by injecting into the coracobrachialis muscle or at the lateral, superficial aspect of the antecubital fossa just above the interepicondylar line. Remember to occlude the axillary vein by using significant transducer pressure

Attempt to block the radial nerve first, as it is deepest and hardest to access – 10 – 15 cc should be adequate at each nerve, however each perineural injection makes visualization more difficult (hence starting with the deepest)

Terminal nerves are difficult to visualize, and at the level of the axillary artery, oftentimes the median nerve is the only one visible – in this instance, deposition of local anesthetic circumferentially surrounding the axillary artery will result in a successful block

Supplementation

The intercostobrachial nerve, originating from the T2 intercostal, is often blocked by the local wheal over the axillary artery in this approach, however to ensure complete blockade, an additional 1-2 mL of local anesthesia can be added superficially around the palpable axillary pulse. The musculocutaneous nerve can be blocked either by injecting into the coracobrachialis muscle or at the lateral, superficial aspect of the antecubital fossa just above the interepicondylar line

Complications

Analysis of the Closed Claims Database suggests that nerve damage is the cause of 16% of claims, with 78% of these occurring under general anesthesia and 22% occurring after regional anesthesia. The ulnar nerve is most commonly injured (28%), followed by the brachial plexus (20%). Keep in mind, however, that Closed Claims Data lacks a denominator [Kroll DA et al. Anesthesiology 73: 202, 1990]

See Also