Dx: Brachial Plexus Block (Interscalene Block)
The goal of this procedure is to anesthetize the nerves of the brachial plexus. This block will provide complete anesthesia to the shoulder, elbow, forearm, and hand. However, unless the musculocutaneous nerve is blocked at the axillary level, you will not achieve anesthesia to the lateral cutaneous nerve which specifically covers the radial aspect of the forearm.
Place the patient in the supine position with the arm resting on the side of the bed. Turn the patient’s head to the opposite side and locate your landmarks.
- Sternal notch
- Clavicular head of the sternocleidomastoid muscle
- Sternal head of the sternocleidomastoid muscle
Using the 10MHz linear array probe, locate your landmarks. The usual sterile prep and drape should be utilized with a sterile probe cover over the linear array probe. Prepare two 10ml syringes of 1% lidocaine for nerve anesthetization with a 27 gauge needle or a spinal needle.
Place the probe on the supraclavicular area above the clavicle. The probe can run parallel to the clavicle with the marker facing left. The brachial plexus will appear in the anatomical triangle between the anterior and middle scalene muscles. The anterior scalene muscle will appear medial to the subclavian artery. Locate the subclavian artery and move the probe laterally along the neck until you locate the fascial nerve sheath and the brachial plexus cluster.
In the long axis view, introduce the 22 gauge needle along the probe. Follow the tip of your needle until you get near the fascial sheath. When in the correct position, withdraw to ensure no intravascular injection and deliver the lidocaine around the nerve sheath. 10-20cc of anesthetic should provide adequate anesthesia for the block.
The most obvious benefit of doing a local nerve block for the emergency physician is the amount of time saved by not performing conscious sedation which requires preparation time, airway supplies, medications which depress the respiratory system, and recovery time.
Baldi et al performed a review of 39 articles from 2005 which examined the advantages of peripheral nerve blocks. These studies demonstrated that direct visualization by ultrasound improved local anesthesia and reduced nerve and vessel injury. Also, cases with obesity, anatomical variance, or abnormal pathology had fewer side effects when visualized by ultrasound.
Lastly, patients that have a higher incidence of complications secondary to conscious sedation, such as patients with COPD, HTN, coronary artery disease, would benefit from nerve blocks by removing the risk of respiratory depression associated with conscious sedation.
The most feared complication of a brachial plexus block is neural damage. Moayeri et al reviewed nerve injury after regional anesthesia to determine incidence. In their review of the literature, they quote 0.03% to 0.4% complications from interscalene brachial plexus block. Animal studies have shown a range from 0 to 5%. Using a noncutting needle such as a spinal needle will decrease the risk of nerve injury in brachial plexus block.
Another common risk of ultrasound guided brachial plexus blocks is misidentification of the nerve plexus for a vascular structure and injecting the artery or vein with anesthetic. It is important to identify anatomical and ultrasound guided landmarks to ensure correct injection of anesthetic around the bracial plexus.
- Ma OJ. Mateer HR. Blaivas M: Emergency Ultraosound, 2nd Edition. McGraw-Hill Companies, Inc.
- Moayeri N, et al: Quantitiative Architecture of the Brachial Plexus and Surround Compartments, and Their Possible Significance for Plexus Blocks. Anestehsiology, V108, No 2, Feb 2008; 299-304.
- Baldi, C et al: Ultrasound Guidance for Locoregional Anesthesia: A review. Minerva Anestesiol 2007; 73: 587-593.
- Antonakakis, J et al: Ultrasound-Guided Regional Anesthesia for Peripheral Nerve Blocks: An Evidence Based Outcome Review. Anesthesiology Clin 29 (2001) 179-191.
- Blaivas, M, and Lyon M: Ultrasound-Guided Interscalene Block for Shoulder Dislocation in the ED. American Journal of Emergency Medicine (2006) 24, 293-296.
Dr. Smalley is a 3rd-year EM Resident. Dr. Kendall is the Director of the Ultrasound Fellowship at Denver Health and Associate Professor at the University of Colorado School of Medicine. Dr. Pryor is a faculty member at Denver Health and is an Assistant Professor of EM at the University of Colorado School of Medicine
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written by Aaron Johnston , November 22, 2011