Axillary Brachial Plexus Block
Indications: Distal upper extremity surgery. Generally limited to analgesia/anesthesia for hand surgery, but when blockade of the musculocutaneous nerve is included, this block is also indicated for wrist and forearm surgery.
Special Considerations: Though limited in extent of coverage, has the advantage of being performed in a superficial, compressible location. Straightforward to place with ultrasound +/- nerve stimulator technique, this is an excellent “beginner’s block” when working with trainees. Particularly useful for bilateral hand surgery (example: syndactyly reconstruction) when phrenic nerve sparing is required.
Coverage: Medial, radial, and ulnar peripheral nerves. The musculocutaneous nerve may be additionally blocked.
Potential Complications:
Very low risk for bleeding due to superficial, compressible block location.
Because multiple separate nerves require blockade in this location, nerve injury secondary to direct needle trauma or intraneural local anesthetic injection must be carefully considered.
Intravascular injection.
Patient Position: Supine, with arm abducted laterally at 90 degrees relative to the body. Elbow may be flexed or kept extended.
Dose: 0.5 - 1.5 mg/kg of Bupivacaine or Ropivacaine (roughly 0.2 - 0.5 mL/kg).
Technique: Probe – Linear; Needle – In-plane
The is probe placed high in the axillary fossa, perpendicularly to the axillary folds. The axillary artery is identified in cross section on ultrasound. Often, the medial, radial, and ulnar nerves can be visualized surrounding the artery, along with multiple axillary veins. Anatomic variation in the location of the nerves and the number of veins is common.
Needle entry is in-plane in a lateral to medial direction along the upper arm. The goal is deposition of local anesthetic in the axillary neurovascular sheath between the axillary artery and the conjoint tendon. This can be achieved either by injecting peri-arterially or by surrounding each individual nerve with local anesthetic. Multiple location(s) for injection using a peri-arterial target are described and offer similar efficacy.
The musculocutaneous nerve lies outside the axillary neurovascular sheath and must be blocked separately for wrist/forearm surgery. Movement of the ultrasound probe slightly laterally and distally allows for location of this hyperechoic nerve in the hypoechoic body of the coracobrachialis muscle. Often this nerve can be blocked by needle redirection after the axillary block is completed, and without the need for a separate skin puncture. Nerve stimulation with biceps twitch can be used as an aid in target confirmation. In the graphic below, the probe has been moved distally, as one can already appreciate the musculocutaneous nerve sandwiched between the biceps and coracobrachialis muscles. Rather than feel obligated to perform axillary and musculocutaneous nerve blocks in separate locations, we tend to scan for an ideal sonographic image where we can perform both simultaneously with one puncture, even if it is a touch more distal.
McN: Musculocutaneous Nerve; MN: Median Nerve; RN: Radial Nerve; UN: Ulnar Nerve; IB: Intercostobrachial nerve
Patient Positioning and Probe Orientation
Expected Dermatomal Coverage
Axillary Block Ultrasound Images
The axillary approach to brachial plexus blockade dates back to the 1800’s and is the most common block used for hand and forearm surgery.
Multiple authors have investigated the ideal location for local anesthetic placement for the axillary brachial plexus block. Cho et al investigated injections at each individual nerve (perineural technique), at the dorsal 12-o’clock position on the artery (single injection perivascular technique), and with local anesthetic split between two injections at the 6-o’clock and 12-o’clock positions on the artery (dual injection perivascular technique). Bernucci et al. and Imasogie et al. examined the perineural technique versus a single deep perivascular injection at 6-o’clock position on the artery. Tran et al, even described injecting perivascularly at 2-,10-, and 6-o’clock on the artery. All authors noted similar success rate, duration of action, and side effect profile, no matter the location of local anesthetic deposition within the axillary neurovascular sheath. They noted that techniques with fewer target locations offered the advantage of simplicity, time efficiency, and decreased number of needle passes.
Thornton et al compared local anesthetic choice specifically for pediatric axillary brachial plexus blockage. They found 0.2% ropivacaine to be as effective as 0.25% bupivacaine when 0.5ml/kg local anesthetic volume was used. When blocking the musculocutaneous nerve, we have found that volumes as low as 0.5-2mL provide sufficient coverage.
Satapathy AR, Coventry DM. Axillary brachial plexus block. Anesthesiol Res Pract. 2011;2011:173796. doi:10.1155/2011/173796.
Cho S, Kim YJ, Baik HJ, Kim JH, Woo JH. Comparison of ultrasound-guided axillary brachial plexus block techniques: perineural injection versus single or double perivascular infiltration. Yonsei Med J. 2015 May;56(3):838-44. doi: 10.3349/ymj.2015.56.3.838. PMID: 25837194; PMCID: PMC4397458.
Bernucci F, Gonzalez AP, Finlayson RJ, Tran DQ. A prospective, randomized comparison between perivascular and perineural ultrasound-guided axillary brachial plexus block. Reg Anesth Pain Med. 2012 Sep-Oct;37(5):473-7. doi: 10.1097/AAP.0b013e3182576b6f. PMID: 22660484.
Imasogie, N., Ganapathy, S., Singh, S., Armstrong, K. and Armstrong, P., 2010. A prospective, randomized, double-blind comparison of ultrasound-guided axillary brachial plexus blocks using 2 versus 4 injections. Anesthesia & Analgesia, 110(4), pp.1222-1226.
Tran DQ, Muñoz L, Zaouter C, Russo G, Finlayson RJ. A prospective, randomized comparison between single- and double-injection, ultrasound-guided supraclavicular brachial plexus block. Reg Anesth Pain Med. 2009 Sep-Oct;34(5):420-4. doi: 10.1097/AAP.0b013e3181ae733a. PMID: 19920418.
Thornton, K.L., Sacks, M.D., Hall, R. and Bingham, R., 2003. Comparison of 0.2% ropivacaine and 0.25% bupivacaine for axillary brachial plexus blocks in paediatric hand surgery. Pediatric Anesthesia, 13(5), pp.409-412.
