Compression of Axillary Artery

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Compression of Axillary Artery

The axillary artery can be palpated in the inferior part of the

lateral wall of the axilla. Compression of the third part of thisartery against the humerus may be necessary when profuse

bleeding occurs (e.g., resulting from a stab or bullet wound in

the axilla). If compression is required at a more proximal site,

the axillary artery can be compressed at its origin (as the

subclavian artery crosses the 1st rib) by exerting downward

pressure in the angle between the clavicle and the inferior

attachment of the sternocleidomastoid.

Aneurysm of Axillary Artery

The first part of the axillary artery may enlarge (aneurysm of

the axillary artery) and compress the trunks of the brachial

plexus, causing pain and anesthesia (loss of sensation) in the

areas of the skin supplied by the affected nerves. Aneurysm of

the axillary artery may occur in baseball pitchers because of

their rapid and forceful arm movements.

Injuries to Axillary Vein

Wounds in the axilla often involve the axillary vein because of

its large size and exposed position. When the arm is fully

abducted, the axillary vein overlaps the axillary artery

anteriorly. A wound in the proximal part of the axillary vein is

particularly dangerous, not only because of profuse bleeding

but also because of the risk of air entering it and producing airemboli(air bubbles) in the blood.

Role of Axillary Vein in Subclavian Vein Puncture


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Subclavian vein puncture, in which a catheter is placed into the

subclavian vein, has become a common clinical procedure (see

blue boxSubclavian Vein Puncture in Chapter 8).

The axillary vein becomes the subclavian vein as the first rib

is crossed. Because the needle is advanced medially to enter

the vein as it crosses the rib, the vein actually punctured (the

point of entry) in a subclavian vein puncture is the terminal

part of the axillary vein. However, the needle tip proceeds into

the lumen of the subclavian vein almost immediately. Thus it is

clinically significant that the axillary vein lies anterior and

inferior (i.e., superficial) to the axillary artery and the parts of

the brachial plexus that begin to surround the artery at thispoint.

Enlargement of Axillary Lymph Nodes

An infection in the upper limb can cause the axillary nodes to

enlarge and become tender and inflamed, a condition

called lymphangitis (inflammation of lymphatic vessels). The

humeral group of nodes is usually the first to be involved.

Lymphangitis is characterized by the development of warm,

red, tender streaks in the skin of the limb. Infections in the

pectoral region and breast, including the superior part of the

abdomen, can also produce enlargement of axillary nodes. In

metastatic cancer of the apical group, the nodes often adhere

to the axillary vein, which may necessitate excision of part of

this vessel. Enlargement of the apical nodes may obstruct the

cephalic vein superior to the pectoralis minor.Dissection of Axillary Lymph Nodes

Excision and pathologic analysis of axillary lymph nodes are

often necessary for staging and determining the appropriate

treatment of a cancer such as breast cancer (seep. 104).
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Because the axillary lymph nodes are arranged and receive

lymph (and therefore metastatic breast cancer cells) in a

specific order, removing and examining the lymph nodes in

that order is important in determining the degree to which the

cancer has developed and is likely to have metastasized.

Lymphatic drainage of the upper limb may be impeded after

the removal of the axillary nodes, resulting

inlymphedema, swelling as a result of accumulated lymph,

especially in the subcutaneous tissue.

During axillary node dissection, two nerves are at risk of

injury. During surgery, the long thoracic nerve to the serratus

anterior is identified and maintained against the thoracic wall.As discussed earlier in this chapter, cutting the long thoracic

nerve results in a winged scapula. If the thoracodorsal nerve to

the latissimus dorsi is cut, medial rotation and adduction of the

arm are weakened, but deformity does not result. If the nodes

around this nerve are obviously malignant, sometimes the

nerve has to be sacrificed as the nodes are resected to increase

the likelihood of complete removal of all malignant cells.

Variations of Brachial Plexus

Variations in the formation of the brachial plexus are common

(Bergman et al., 1988). In addition to the five anterior rami

(C5C8 and T1) that form the roots of the brachial plexus,

small contributions may be made by the anterior rami of C4 or

T2. When the superiormost root (anterior ramus) of the plexus

is C4 and the inferiormost root is C8, it is aprefixed brachialplexus.Alternately, when the superior root is C6 and the inferior

root is T2, it is apostfixed brachial plexus. In the latter type,

the inferior trunk of the plexus may be compressed by the 1st

rib, producing neurovascular symptoms in the upper limb.

Variations may also occur in the formation of trunks, divisions,
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and cords; in the origin and/or combination of branches; and in

the relationship to the axillary artery and scalene muscles. For

example, the lateral or medial cords may receive fibers from

anterior rami inferior or superior to the usual levels,

respectively.

In some individuals, trunk divisions or cord formations may

be absent in one or other parts of the plexus; however, the

makeup of the terminal branches is unchanged. Because each

peripheral nerve is a collection of nerve fibers bound together

by connective tissue, it is understandable that the median

nerve, for instance, may have two medial roots instead of one

(i.e., the nerve fibers are simply grouped differently). Thisresults from the fibers of the medial cord of the brachial plexus

dividing into three branches, two forming the median nerve

and the third forming the ulnar nerve. Sometimes it may be

more confusing when the two medial roots are completely

separate; however, understand that although the median nerve

may have two medial roots the components of the nerve are

the same (i.e., the impulses arise from the same place and

reach the same destination whether they go through one ortwo roots).

Brachial Plexus Injuries

Injuries to the brachial plexus affect movements and cutaneous

sensations in the upper limb. Disease, stretching, and wounds

in the lateral cervical region (posterior triangle) of the neck

(seeChapter 8) or in the axilla may produce brachial plexusinjuries. Signs and symptoms depend on the part of the plexus

involved. Injuries to the brachial plexus result

inparalysis andanesthesia.Testing the persons ability to

perform movements assesses the degree of paralysis.

In complete paralysis, no movement is detectable.
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In incomplete paralysis, not all muscles are paralyzed;

therefore, the person can move, but the movements are weak

compared with those on the normal side. Determining the

ability of the person to feel pain (e.g., from a pinprick of the

skin) tests the degree of anesthesia.

Injuries to superior parts of the brachial plexus (C5 and C6)

usually result from an excessive increase in the angle between

the neck and the shoulder. These injuries can occur in a person

who is thrown from a motorcycle or a horse and lands on the

shoulder in a way that widely separates the neck and shoulder

(Fig. B6.12A). When thrown, the persons shoulder often hits

something (e.g., a tree or the ground) and stops, but the headand trunk continue to move. This stretches or ruptures superior

parts of the brachial plexus or avulses (tears) the roots of the

plexus from the spinal cord.
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Compression of Axillary Artery