INFRACLAVICULAR BRACHIAL PLEXUS BLOCK AT A GLANCE
Indications: arm, elbow, forearm, and hand surgery (Figure 32D-1)
Transducer position: approximately parasagittal, just medial to the coracoid process, inferior to the clavicle
Goal: local anesthetic spread around axillary artery
Local anesthetic volume: 20–30 mL
Distribution of sensory blockade of the infraclavicular brachial plexus block.
The ultrasound (US)-guided infraclavicular brachial plexus block is in some ways both simple and challenging. It is simple in that identification of the arterial pulse on the sonographic image is an easy primary goal in establishing the landmark. However, the plexus at this level is situated deeper, and the angle of approach is more acute, making simultaneous visualization of the needle and the relevant anatomy more challenging. Fortunately, although it is not always possible to reliably identify the three cords of the plexus, adequate block can be achieved by simply depositing the local anesthetic in a U shape around the artery. The infraclavicular brachial plexus block is well suited for the catheter technique because the musculature of the chest wall helps stabilize the catheter and prevents its dislodgement compared with the more superficial location used with the interscalene and supraclavicular approaches to brachial plexus blockade.
The axillary artery can be identified deep to the pectoralis major and minor muscles. An effort needs to be made to obtain clear views of both pectoralis muscles and their respective fasciae. This is important because the area of interest lies underneath the fascia of the pectoralis minor muscle. Surrounding the artery are the three cords of the brachial plexus: the lateral, posterior, and medial cords. These are named for their usual position relative to the axillary artery, although there is a great deal of anatomical variation. With the left side of the screen corresponding to the cephalad aspect, the cords can often be seen as round hyperechoic structures at the positions of approximately 9 o’clock (lateral cord), 7 o’clock (posterior cord), and 5 o’clock (medial cord) (Figures 32D–2 and 32D–3). The axillary vein is seen as a compressible hypoechoic structure that lies medially to the axillary artery. Multiple other, smaller vessels (eg, the cephalic vein) are often present as well. The transducer is moved in the cephalad-caudad and medial-lateral direction until the artery is identified in cross-section. Depending on the depth selected and the level at which the scanning is performed, the chest wall and the pleura may be seen in the medial and more caudal aspect of the image. The axillary artery and/or brachial plexus are typically identified at a depth of 3–5 cm in average-size patients.
Anatomy of the infraclavicular brachial plexus (BP) and the position of the transducer. Paramedian sagittal plane at the level of the coracoid process. The ...