**13. Supraclavicular approach of brachial plexus**

The supraclavicular fossa is limited by the outer edge of the sternocleidomastoid muscle, the middle third clavicular and the anterior border of trapezius. When the trunks of the brachial plexus abandon the interscalene space, they form 6 divisions, 3 above and 3 below. The brachial plexus is directed from the corresponding interscalene space to the axilla, passing over the 1st rib between the attachments of the anterior and middle scalene muscles, and below the collarbone. When the plexus lies between the first rib and the clavicle, it remains surrounded by a fascial sheath, maintaining a close relationship to the subclavian artery, although extending above and remaining external to it. The subclavian vein is located above the 1st rib and enters into the anterior scalene muscle.

For ultrasound imaging of the brachial plexus, the supraclavicular ultrasound probe should be placed in the supraclavicular fossa, parallel to the clavicle and the edge, touching its inside while at an angle to the chest. This represents the "guide" to locate the subclavian artery. It is desirable that this approach is made at a level that includes the artery in the center of the image, clearly positioned on the first rib, leaving the farthest edge of the pleura on each side. In that way, the nerves will be situated in a superior position external to the artery. It is sometimes possible to observe a cross-section of the subclavian vein, which appears as a hypoechoic round structure that does not pulsate, with internal strings of images that correspond to valvular structures. Anatomically, it is situated before the insertion of anterior scalenus muscle, and thus medial to the muscle in the image, and in most cases it is obscured by the clavicle.
