- Indications: arm, elbow, forearm, and hand surgery
- Transducer position: transverse on neck, just superior to the clavicle at midpoint
- Goal: local anesthetic spread around brachial plexus, lateral and superficial to subclavian artery
- Local anesthetic: 20–25 mL
Supraclavicular brachial plexus; transducer position and needle insertion.
The proximity of the brachial plexus at this location to the chest cavity and pleura, has been of concern to many practitioners (Figure 30-2). However, ultrasound guidance has resulted in a resurgence of interest in the supraclavicular approach to the brachial plexus. The ability to image the plexus, rib, pleura, and subclavian artery with ultrasound guidance has increased safety due to better monitoring of anatomy and needle placement. Because the trunks and divisions of the brachial plexus are relatively close as they travel over the first rib, the onset and quality of anesthesia is fast and complete. For these reasons, the supraclavicular block has become a popular technique for surgery below the shoulder.
Anatomy of the supraclavicular brachial plexus with proper transducer placement slightly obliquely above the clavicle (Cl). SA, subclavian artery; arrow, brachial plexus (BP).
The subclavian artery crosses over the first rib between the insertions of the anterior and middle scalene muscles, at approximately the midpoint of the clavicle. The pulsating subclavian artery is readily apparent, whereas the parietal pleura and the first rib can be seen as a linear hyperechoic structure immediately lateral and deep to it, respectively (Figure 30-3). The rib, as an osseous structure, casts an acoustic shadow, so that the image field deep to the rib appears anechoic, or dark. A reverberation artifact (refer to Chapter 26) often occurs, mimicking a second subclavian artery beneath the rib. The brachial plexus can be seen as a bundle of hypoechoic round nodules (e.g., "grapes") just lateral and superficial to the artery (Figures 30-3, 30-4, 30-5A and B). It is often possible to see the fascial sheath enveloping the brachial plexus. Depending at the level at which the plexus is scanned and the transducer orientation, brachial plexus can have an oval or flattened appearance (Figure 30-5A and B). Two different sonographic appearances of the brachial plexus (one oval and one flattened) are easily seen by changing the angle of the transducer orientation during imaging. Lateral and medial to the first rib is the hyperechoic pleura, with lung tissue deep to it. This structure can be confirmed by observation of a "sliding" motion of the viscera pleura with the patient's respiration. The brachial plexus is typically visualized at a 1- to 2-cm depth at this location, an important anatomical characteristic of the plexus that must be kept in mind throughout the procedure.