Peripheral Nerve Blocks: A Color Atlas, 3rd Edition

36. Ultrasound Guided Axillary Block

Paul Bigeleisen

Steve Orebaugh

Patient Position: Supine, with ipsilateral arm abducted, externally rotated, and flexed at the elbow.

Indications: Elbow, forearm, and hand surgery.

Needle Size: 22-gauge, 50-mm insulated needle.

Volume: 15 to 25 mL.

Ultrasonographic Landmarks: The biceps muscle lies anterosuperior to the neurovascular bundle, while the coracobrachialis muscle is superior to the neurovascular bundle, and the triceps muscle, inferior to neurovascular bundle. The humerus lies deep to the neurovascular bundle. The brachial artery and 1 to 2 brachial veins are evident in the neurovascular bundle. The radial, median, and ulnar nerves are found within the neurovascular bundle (Fig. 36-1A, C). Most commonly, the median nerve is anterior or cephaloanterior to the artery. The radial nerve is most commonly posterior or posteroinferior to the artery, while the ulnar nerve is most commonly found inferior or anteroinferior to the artery. Proximal in the axilla, the musculocutaneous nerve may be found cephaloposterior to the artery. In more distal sites in the axilla, the musculocutaneous nerve is usually found in the fascia between the biceps and coracobrachialis muscles 1 to 2 cm cephaloposterior to the artery. Cutaneous nerves of the arm or forearm may also be visualized.

Transducer Position: Transverse across the axilla (sagittal oblique), placed at the intersection of the pectoralis and biceps muscles.

Technique: Place sterile skin prep solution on the field. Cover the transducer with a sterile cover, and place sterile sonographic gel over the skin in the field. A wheel of local anesthetic should be injected beneath the skin along a 5 cm arc from medial to lateral to the brachial artery pulsation (Fig. 36-1A). This allows needle placement from either side of the artery, without repeatedly injecting subcutaneously local anesthetic, as well as providing anesthesia for the intercostobrachial nerve and the medial brachial cutaneous nerve.

The artery should be localized with the transducer, and the hyperechoic nerves sought at its periphery. Initially, the block needle is inserted in-plane, along the long axis of the transducer, from the superior side of the artery (Fig. 36-1A). In the posterocephalad region, the musculocutaneous nerve is sought. The peripheral nerve stimulator may be left on throughout the procedure, with a current level of 0.5 to 1 mA, or it may be switched on as each nerve is approached, then turned off after confirmation. When elbow flexion occurs, the nerve is localized. The stimulator can be switched off, and incremental injections of 2 to 3 mL of local anesthetic are begun. A “halo” of local anesthetic should be created around the nerve. A total of 5 mL is injected here.

Figure 36-1. PM, pectoralis major; MC, musculocutaneous; BC, biceps; CB, coracobrachialis; M, median; V, axillary vein; A, axillary vein; U, ulnar; DBA, deep brachial artery; R, radial; H, humerus.

The needle is then withdrawn and redirected toward the median nerve, if evident, or to the region anterior and/or superior to the artery. The nerve stimulator may be left on throughout the procedure, or turned on at this time. When appropriate motor or cutaneous stimulation confirms contact with the nerve, local anesthetic is incrementally injected (5 mL) until a halo appears around the nerve. The needle is then removed from the skin, and its entry point shifted to the caudal edge of the transducer. After insertion in-plane, it is directed to the ulnar nerve, if evident, or to the inferior edge of the artery. When motor or sensory stimulation of the ulnar nerve occurs, 5 mL of local anesthetic is injected as described previously. Finally, the needle is redirected more posterior, and guided to the radial nerve. After confirmation of the nerve with motor or sensory stimulation, 5 mL of local anesthetic is injected incrementally, following the procedure outlined above.


1.   Veins may vary in number, with one, two, or even more being present. They are easily compressed, and care must be taken to note their position, as even mild pressure with the transducer can obliterate the lumen on the ultrasound image. Five to ten percent of patients will have an accessory axillary artery located deep or posterior to the primary axillary artery.

2.   It is difficult to contact and anesthetize all four nerve blocks from one needle insertion site due to the location of the nerves around the circumference of the artery and the variable location of the musculocutaneous nerve.

Suggested Readings

Bigeleisen P. The bifid axillary artery. J Clin Anesth 2004;16:224–225.

Casati A, Danelli G, Baciarello M, et al. A prospective, randomized comparison between ultrasound and nerve stimulation guidance for multiple injection axillary brachial plexus block. Anesthesiology 2007;106:992–996.

Kovacs P, Gruber H, Bodner G. Interventional techniques. In: Peer S, Bodner G, eds. High resolution sonography of the peripheral nervous system. Springer-Verlag, Berlin, 2003:94–104.

Retzl G, Kapral S, Greher M, et al. Ultrasonographic findings of the axillary part of the brachial plexus. Anesth Analg 2001;92:1271–1275.

Schafhalter-Zoppoth I, Gray AT. The musculocutaneous nerve: ultrasound appearance for peripheral nerve block. Reg Anesth Pain Med 2005;30:385–390.