Fig. 1. (A ) Illustration of the point of needle insertion. The patient is in a supine position with the right arm abducted 90° and maximally rotated externally, exposing the medial surface of the arm. The cannula with an outside catheter was inserted immediately superior to the brachial artery, approximately 4 cm distal to the lateral border of the pectoralis major muscle. It was directed toward the axilla, parallel to the artery. The initial cannula angle to the skin was 30–40°. After fascial click, the cannula–catheter was advanced (aided by a nerve stimulator) with a flat angle to the skin. The catheter was taped in median nerve–stimulating position. Subsequently, the cannula was withdrawn and a flexible extension tube was connected to the catheter for later injections of local anesthetic. (B ) Schematic cross-sectional drawing from the right arm illustrating the quadrant system around the brachial artery and the common position of the four terminal nerves. The musculocutaneous nerve is usually found in the deep superior quadrant (Q¹), the median nerve in the superficial superior quadrant (Q²), the ulnar nerve in the superficial inferior quadrant (Q³), and the radial nerve in the deep inferior quadrant (Q⁴). The terms deep  and superficial  refer to the medial surface of the arm.