Anesthesiology, Article

Ultrasound-guided axillary nerve block for ED incision and drainage of deltoid abscess

a b s t r a c t

Deltoid abscesses are common and painful, often a consequence of injection drug use and seen frequent- ly in emergency departments (EDs). The required incision and drainage can be completed successfully with effective pain relief using a peripheral nerve block. The brachial plexus nerve block works well, however it is technically complex with a low, but potentially serious, risk of complications such as phrenic nerve paralysis. Selective blockade of the axillary nerve eliminates the risks associated with a brachial plexus block, while providing more specific anesthesia for the deltoid region. Our initial experi- ence suggests that the axillary nerve block (ANB) is a technically simple, safe, and effective way to man- age the pain of deltoid abscesses and the necessary incision and drainage (I&D). The block involves using ultrasound guidance to inject a 20 mL bolus of local anesthetic into the quadrangular space surrounding the axillary nerve (inferior to the posterolateral aspect of the acromion, near the overlap of the long head of triceps brachii and teres minor). Once injected the local will anesthetize the axillary nerve resulting in analgesia of the cutaneous area of the lateral shoulder and the deeper tissues including the deltoid muscle.

Further research will clarify questions about the volume and concentration of local anesthetic, the role of injected adjuncts, and expected duration of analgesia and anesthesia. Herein we present a description of an axillary nerve block successfully used for deltoid abscess I&D in the ED.

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Introduction and anatomic basis of the axillary nerve block

The axillary nerve forms from the ventral rami roots of C5 and C6 (the terminal branch off the posterior cord of the brachial plexus). The axillary nerve lies posterior to the axillary artery and anterior to the subscapularis muscles, it travels to the border of the inferior edge of subscapularis and then courses through the quadrangular space and bi- furcates into anterior and posterior branches. The quadrangular space is a pathway for the neuromuscular structures to move from the axilla to the posterior aspect of the arm; the boundaries are formed by subscapularis and teres minor (superior), teres major (inferior), the

? Funding sources/disclosures: none.

* Corresponding author at: Department of Emergency Medicine, Highland Hospital–Alameda Health System, 1411 East 31st Street, Oakland, CA 94602-1018, United States.

E-mail address: [email protected] (A.A. Herring).

surgical neck of the humerus (lateral), and long head of triceps brachii (medial).

The posterior branch of the axillary nerve provides motor innerva- tion to teres minor and cutaneous innervation to the skin over the infe- rior aspect of the deltoid. The anterior branch wraps around the humerus, deep to the deltoid muscle and sends fibers into the muscle. The superior lateral cutaneous nerve of the arm also branches off at this point, supplying the Shoulder joint tissues and most of the skin sur- rounding the deltoid muscles (Figs. 1a,b,c). The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and can thus be well visualized on ultrasound with the typical honeycomb appearance.

The most convenient method to perform the axillary nerve block (ANB) is to have the patient laying prone, with the ultrasound probe in-line with the long axis of the humerus. The teres minor muscle can be seen tucked in from the medial side, underneath the large deltoid muscle like a “little thumb.” At the tip of the “thumb” the axillary nerve and Circumflex artery can be visualized (Fig. 2). Carefully injecting local anesthetic will produce enough anesthesia of the cutaneous skin

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over the deltoid to allow for incision and drainage of deltoid abscesses. This block is straightforward, has an improved safety profile compared to interscalene blocks, and is appropriate for emergency providers fa- miliar with ultrasound-guided procedures.


A 27-year-old female with a right deltoid abscess after injecting her- oin 3 days prior.

Fig. 1. Axillary nerve course and distribution. A. The axillary nerve originates from the posterior cord of the brachial plexus, carrying fibers from C5 and C6 and travels through the quadrangular space with the posterior circumflex humeral artery and vein. The anterior branch provides motor to the anterior deltoid as well as some cutaneous branches, while the posterior branch supplies teres minor, posterior deltoid motor, and supplies sensory to the skin of the lower 2/3 of the deltoid muscle and the skin covering the long head of triceps brachii. When the axillary nerve block (ANB) is performed, local anesthetic is deposited directly in contact with the axillary nerve, as it emerges inferior to teres minor. B. Upper extremity dermatome map. C. Cutaneous innervation of the upper extremity.

Fig. 1 (continued).

Axillary nerve block technique

Informed consent

We explained the block would last 2-3 h, with the possibility of se- vere rebound pain, block failure, and Local anesthetic toxicity (LAST).


cardiac monitoring, an IV line, and access to Intralipid(R) were con-

firmed. A 80 mm 22-gauge Touhy needle, extension tubing, and a

30 mL syringe loaded with 20 mL 1.5% mepivacaine and 3 mL of 1% lido- caine loaded in a 5 mL syringe with a 27-gauge needle were prepared. Standard sterile techniques were observed with an adhesive sterile probe cover, sterile gloves, and sterile drape.


The patient was placed laying prone. The block can also be per- formed in a sitting position, however prone facilitates holding the probe steady. The needle was targeted toward the postero-medial as- pect of the humerus just inferior to teres minor muscle (Fig. 3).

Fig. 2. Surface Anatomy and patient positioning for the Axillary Nerve Block. A. The deltoid muscle originates as muscle branches from the clavicle, acromion and scapula and inserts on the deltoid tuberosity of the humerus. B. Posterior approach. The patient is placed in a prone position with the ultrasound machine positioned for easy line-of-site, with the transducer in-line with the humerus in a roughly sagittal orientation approximately 4 cm inferior to the posterior aspect of the acromion.


The needle was advanced in-plane, under ultrasound-guidance to the plane deep to the deltoid muscle to the neurovascular area cranial to the posterior circumflex artery (Fig. 2). After negative aspiration, a test dose of 3 mL confirmed proper needle tip placement with opening of the intramuscular layer. Injection continued under ultrasound-guid- ance with aliquots of 3-5 mL after negative aspiration until 20 mL of 1.5% mepivacaine was administered (Figs. 2, 4). The patient experienced no cardiac events or signs of local anesthetic toxicity. She was able to tolerate successful incision and drainage of the abscess without any se- dation, and in fact slept through the procedure. The patient was discharged home the same day (Fig. 5).


Our case suggests a role for the ANB in the ED treatment of deltoid abscess. Deltoid abscesses are common and painful. Use of the ANB for

Fig. 3. Prone patient positioning provides convenient access to the posterior aspect of the shoulder for an in-plane injection.

incision and drainage may help improve patient satisfaction with the procedure as well as avoid the need for resource intensive procedural sedation. We applied the ANB to emergency incision and drainage of deltoid abscess patients based on the initial description by Checcucci et al. [1], and additional case reports describing axillary nerve block for treating post-operative shoulder pain [2-4]. The major risk is intra- vascular injection of anesthetic into the posterior circumflex artery, which is mitigated through ultrasound-guidance and aspiration prior to injection. Nerve injury is unlikely. Further study is needed to deter- mine the ideal volume of anesthetic. Very large abscesses that track down the arm toward the axilla or elbow may require additional local infiltration or use of a brachial plexus block and/or serratus plane block. In summary, our preliminary experience suggests the ANB is techni- cally easy and may be preferred over interscalene block or procedural

sedation for I&D of deltoid abscesses in the ED.

Fig. 4. Post-injection ultrasound image of the axillary nerve shows nerve surrounded with local anesthetic.

Fig. 5. Successful incision and drainage performed with a selective axillary nerve block in a high-risk patient without the need for procedural sedation.

block and an axillary nerve block: an evaluation of the first results. Arthrosc: J Arthrosc Relat Surg 2008;24(6):689-96.

Kim YA, Yoon KB, Kwon TD, Kim DH, Yoon DM. Evaluation of Anatomic landmarks for axillary nerve block in the quadrilateral space. Acta Anaesthesiol Scand 2014;58(5): 67-71.
  • Nam YS, Jeong JJ, Han SH, Park SE, Lee SM, Kwon MJ, et al. An anatomic and clinical study of the suprascapular and axillary nerve blocks for shoulder arthroscopy. J Shoul- der Elbow Surg/Am Should Elb Surg 2011;20(7):1061-8.
  • Roche C, Asghar S, Andersen HL, Christensen JK, Lange KH. Ultrasound-guided block of the axillary nerve: a volunteer study of a new method. Acta Anaesthesiol Scand 2011;55(5):565-70.
  • References

    1. Checcucci G, Allegra A, Bigazzi P, Gianesello L, Ceruso M, Gritti G. A new technique for regional anesthesia for arthroscopic shoulder surgery based on a suprascapular nerve

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