Fig. 48—The brachial artery. (Gray)
The brachial artery is one continuous vessel, the entire length of the upper arm, and varies in size according to the size of the person and the development of the arm. It is accompanied by the venae comites or deep brachial veins, the one to the inner side of the artery about one-third to one-half the size of the artery, the other about one-half its size lies directly underneath. All are encased in the same common sheath of deep fascia that surrounds and holds them together. Great care, then, should be taken to separate the artery from these veins before cutting the artery for injection.
The artery lies along the inner and under border of the large muscle on top of the arm known as the biceps. The biceps is the muscle used when lifting a weight. To those whose occupation is to exercise the muscular tissue of the body liberally, this muscle becomes quite large, and generally the artery is proportionally large.
Linear Guide.—The course of the brachial artery may be marked out by drawing a line from the middle of the axillary space (arm pit) to the center of the elbow, provided the palm of the hand be turned upward. This line will be immediately over the artery, which will be found by cutting through the skin at any point on the line, and dissecting through the subcutaneous tissue toward the center of the arm.
The Anatomical Guide.—In the upper third the artery lies between the biceps and coracobrachialis muscles which lie above the artery, and the triceps muscle which lies below the artery. In the upper third the nerve lies close to the muscle, the artery below and to the inner side toward the body, and the vein a little farther to the inside.
In the middle third the artery lies between the biceps which lies above the artery, and the triceps muscle which lies below the artery. In the middle third the artery will lie beneath the nerve.
In the lower third the artery lies between the biceps which lies above the artery, and the triceps which lies below the artery. In the lower third the artery lies next to the muscle and the nerve to the inner side next to the body, and the vein still farther to the inner side.
How to Raise the Artery.—First trace the inner border of the biceps muscle, feel for the median nerve, which will always be present. The artery in the middle and lower thirds will follow the border of the muscle. The palm of the hand should always be turned upward, and the linear guide, as stated above, will indicate the exact position of the artery. Make an incision through the skin, on the linear guide, pushing the fatty subcutaneous tissue to one side, if there be any, and with the handle of the scalpel, work through the superficial fascia. Reverse the blade, and at each end of the incision, cut forward and upward to make it clean. Now with the scalpel cautiously cut through the deep fascia, and remove this from the vessels below. This will expose to view the median nerve, and with the handle of the scalpel, separate the tissue between the artery and the muscle, and between the artery and the nerve. Having thus freed the artery, use the hook end of the aneurism needle and pass it under the artery toward the muscle, and raise the artery to the surface. Pass the bone separator or the forceps with the closed end, underneath, remove the sheath surrounding the artery and the deep brachial veins. The natural position will be, the artery on top, the larger deep brachial vein to the inner side and the smaller one underneath. It is very necessary to remove these deep brachial veins, for the reason that if they are not, in cutting the artery for injection, they will be cut also, resulting in a flow of venous blood into the incision.