SUPRACLAVICULAR BRACHIAL PLEXUS BLOCK AT A GLANCE
Indications: arm, elbow, forearm, hand surgery; anesthesia for shoulder surgery is also possible (Figure 32C–1).1
Transducer position: transverse on neck, just superior to the clavicle at the midpoint (Figure 32C–1)
Goal: local anesthetic spread around the brachial plexus, posterior and superficial to the subclavian artery
Local anesthetic: 20–25 mL
Expected sensory distribution of the supraclavicular brachial plexus block.
At this location, the proximity of the brachial plexus to the chest cavity and pleura had been of concern (Figure 32C–2) until ultrasound (US) guidance renewed interest in the supraclavicular approach to the brachial plexus block. The ability to image the plexus, rib, pleura, and subclavian artery with US has increased safety due to improved monitoring of anatomy and needle placement. Because the trunks and divisions of the brachial plexus are relatively close as they pass over the first rib, the extension and quality of anesthesia are favorable. For these reasons, the supraclavicular block has become a commonly used technique for surgery of the upper limb distal to the shoulder.
Anatomy of the supraclavicular brachial plexus with proper transducer placement slightly oblique above the clavicle (Cl). Yellow arrow: brachial plexus (BP). SA, subclavian artery.
The subclavian artery crosses over the first rib between the insertions of the anterior and middle scalene muscles, posterior to the midpoint of the clavicle. The subclavian artery is readily apparent as an anechoic round structure, whereas the parietal pleura and the first rib can be seen as a linear hyperechoic structure immediately lateral and deep to the subclavian artery (Figure 32C–3). The rib casts an acoustic shadow so that the image field deep to the rib appears anechoic.2 The brachial plexus can be seen as a bundle of hypoechoic round nodules just posterior and superficial to the artery (Figures 32C–3 and 32C–4). It is often possible to see the fascial sheath of the muscles surrounding the brachial plexus. Adjusting the transducer orientation, the upper, middle and lower trunks of the brachial plexus can be individually identified, as they join together at the costoclavicular space. To visualize the lower trunk, the transducer is oriented in the sagittal plane, until the first rib is seen deep to the plexus and the artery. (Figure 32C-4). Anterior or posterior to the first rib is the hyperechoic pleura, with lung tissue deep to it. This structure can be confirmed by observing a “sliding” motion of the viscera l pleura in synchrony with the patient’s respiration. The brachial plexus is typically visualized at a 1- to 2-cm depth at this location.