- Indications: arm, elbow, forearm, and hand surgery
- Transducer position: approximately parasagittal, just medial to coracoid process, inferior to clavicle
- Goal: local anesthetic spread around axillary artery
- Local anesthetic volume: 20–30 mL
In-plane needle insertion technique during infraclavicular brachial plexus block.
The ultrasound-guided infraclavicular brachial plexus block is in some ways both simple and challenging. It is simple in the sense that geometric measuring of distances and angles on the surface of the patient, as is the case with the nerve stimulator–based technique, is not required. 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 at this position, adequate block can be achieved by simply depositing the local anesthetic in a "U" shape around the artery. Infraclavicular block is well-suited for catheter technique because the musculature of the chest wall helps stabilize the catheter and prevents its dislodgment compared with the more superficial location with the interscalene or supraclavicular approaches.
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 anatomic variation. With the left side of the screen corresponding to the cephalad aspect, the cords can often be seen as round hyperechoic structures at approximately 9 o'clock (lateral cord), 7 o'clock (posterior cord), and 5 o'clock (medial cord) (Figures 31-2, 31-3, and 31-4). The axillary vein is seen as a compressible hypoechoic structure that lies inferior, or slightly superficial, to the axillary artery. Multiple other, smaller vessels (e.g., the cephalic vein) are often present as well. The transducer is moved in the superior-inferior direction until the artery is identified in cross-section. Depending on the depth of field selected and the level at which the scanning is performed, the chest wall and lung may be seen in the inferior aspect of the image. The axillary artery and/or brachial plexus are typically identified at a depth of 3 to 5 cm in average size patients.
Anatomy of the infraclavicular brachial plexus and the position of the transducer. Brachial plexus (BP) is seen surrounding the axillary artery (AA) underneath the clavicle ...