INTERSCALENE BRACHIAL PLEXUS BLOCK AT A GLANCE
Indications: shoulder and upper arm surgery, surgery of the clavicle (combined with cervical plexus block)
Transducer position: transverse on neck, 3–4 cm superior to clavicle, over external jugular vein (Figure 32B–1)
Goal: local anesthetic spread around superior and middle trunks of brachial plexus, between the anterior and middle scalene muscles
Local anesthetic: 7–15 mL
Ultrasound-guided interscalene brachial plexus block: transducer and needle position to obtain the desired ultrasound image for an in-plane approach. The knowledge of external landmarks substantially facilitates and shortens the time to obtain the view necessary for block performance. The transducer is positioned behind the clavicular head of the sternocleidomastoid muscle (SCM) and over the external jugular vein (not seen). The patient is in a semi-sitting position. Tilting the transducer in the caudad direction can facilitate recognition of the brachial plexus (arrow).
US guidance allows for visualization of the spread of the LA and additional injections around the brachial plexus if needed to ensure adequate spread of local anesthetic, improving block success. The ability to visualize local anesthetic spread and to inject multiple aliquots also allows for a reduction in the volume of local anesthetic required to accomplish the block.1,2
The brachial plexus at the interscalene level is seen lateral to the carotid artery and internal jugular vein, between the anterior and middle scalene muscles (Figures 32B–2 and 32B–3). The prevertebral fascia, superficial cervical plexus, and sternocleidomastoid muscle are seen superficial to the plexus. The transducer is moved in the proximal-distal direction until two or more of the brachial plexus elements are seen in the space between the scalene muscles. Depending on the depth of field selected and the level at which scanning is performed, the first rib and/or the apex of the lung may be seen. The brachial plexus is typically visualized at a depth of 1–3 cm.
Relevant anatomy for interscalene brachial block and transducer position to obtain the desired views. The brachial plexus (BP) is seen between middle scalene muscle (MSM) laterally and the anterior scalene muscle (ASM) medially. The ultrasound image often includes a partial view of the lateral border of the sternocleidomastoid muscle (SCM) as well as the internal jugular vein (IJV) and carotid artery (CA). The transverse process of one of the cervical vertebrae is also often seen.
Ultrasound image of the brachial plexus at the interscalene groove. The BP is seen positioned between the anterior scalene muscle (ASM) and the middle scalene muscle (MSM). In this particular image, the vertebral artery (VA), carotid artery (CA), and the transverse process of C7 (TP-C7) are ...