The following description of the injuries of arteries refers to the larger, named trunks. The injuries of smaller, unnamed vessels are included in the consideration of wounds and contusions.
Contusion.—An artery may be contused by a blow or crush, or by the oblique impact of a bullet. The bruising of the vessel wall, especially if it is diseased, may result in the formation of a thrombus which occludes the lumen temporarily or even permanently, and in rare cases may lead to gangrene of the limb beyond.
Subcutaneous Rupture.—An artery may be ruptured subcutaneously by a blow or crush, or by a displaced fragment of bone. This injury has been produced also during attempts to reduce dislocations, especially those of old standing at the shoulder. It is most liable to occur when the vessels are diseased. The rupture may be incomplete or complete.
Incomplete Subcutaneous Rupture.—In the majority of cases the rupture is incomplete—the inner and middle coats being torn, while the outer remains intact. The middle coat contracts and retracts, and the internal, because of its elasticity, curls up in the interior of the vessel, forming a valvular obstruction to the blood-flow. In most cases this results in the formation of a thrombus which occludes the vessel. In some cases the blood-pressure gradually distends the injured segment of the vessel wall and leads to the formation of an aneurysm.
The pulsation in the vessels beyond the seat of rupture is arrested—for a time at least—owing to the occlusion of the vessel, and the limb becomes cold and powerless. The pulsation seldom returns within five or six weeks of the injury, if indeed it is not permanently arrested, but, as a rule, a collateral circulation is rapidly established, sufficient to nourish the parts beyond. If the pulsation returns within a week of the injury, the presumption is that the occlusion was due to pressure from without—for example, by hæmorrhage into the sheath or the pressure of a fragment of bone.
Complete Subcutaneous Rupture.—When the rupture is complete, all the coats of the vessel are torn and the blood escapes into the surrounding tissues. If the original injury is attended with much shock, the bleeding may not take place until the period of reaction. Rupture of the popliteal artery in association with fracture of the femur, or of the axillary or brachial artery with fracture of the humerus or dislocation of the shoulder, are familiar examples of this injury.
Like incomplete rupture, this lesion is accompanied by loss of pulsation and power, and by coldness of the limb beyond; a tense and excessively painful swelling rapidly appears in the region of the injury, and, where the cellular tissue is loose, may attain a considerable size. The pressure of the effused blood occludes the veins and leads to congestion and œdema of the limb beyond. The interference with the circulation, and the damage to the tissues, may be so great that gangrene ensues.
Treatment.—When an artery has been contused or ruptured, the limb must be placed in the most favourable condition for restoration of the circulation. The skin is disinfected and the limb wrapped in cotton wool to conserve its heat, and elevated to such an extent as to promote the venous return without at the same time interfering with the inflow of blood. A careful watch must be kept on the state of nutrition of the limb, lest gangrene occurs.
If no complications supervene, the swelling subsides, and recovery may be complete in six or eight weeks. If the extravasation is great and the skin threatens to give way, or if the vitality of the limb is seriously endangered, it is advisable to expose the injured vessel, and, after clearing away the clots, to attempt to suture the rent in the artery, or, if torn across, to join the ends after paring the bruised edges. If this is impracticable, a ligature is applied above and below the rupture. If gangrene ensues, amputation must be performed.
These descriptions apply to the larger arteries of the extremities. A good illustration of subcutaneous rupture of the arteries of the head is afforded by the tearing of the middle meningeal artery caused by the application of blunt violence to the skull; and of the arteries of the trunk—caused by the tearing of the renal artery in rupture of the kidney.
Open Wounds of Arteries—Laceration.—Laceration of large arteries is a common complication of machinery and railway accidents. The violence being usually of a tearing, twisting, or crushing nature, such injuries are seldom associated with much hæmorrhage, as torn or crushed vessels quickly become occluded by contraction and retraction of their coats and by the formation of a clot. A whole limb even may be avulsed from the body with comparatively little loss of blood. The risk in such cases is secondary hæmorrhage resulting from pyogenic infection.
The treatment is that applicable to all wounds, with, in addition, the ligation of the lacerated vessels.
Punctured wounds of blood vessels may result from stabs, or they may be accidentally inflicted in the course of an operation.
The division of the coats of the vessel being incomplete, the natural hæmostasis that results from curling up of the intima and contraction of the media, fails to take place, and bleeding goes on into the surrounding tissues, and externally. If the sheath of the vessel is not widely damaged, the gradually increasing tension of the extravasated blood retained within it may ultimately arrest the hæmorrhage. A clot then forms between the lips of the wound in the vessel wall and projects for a short distance into the lumen, without, however, materially interfering with the flow through the vessel. The organisation of this clot results in the healing of the wound in the vessel wall.
In other cases the blood escapes beyond the sheath and collects in the surrounding tissues, and a traumatic aneurysm results. Secondary hæmorrhage may occur if the wound becomes infected.
The treatment consists in enlarging the external wound to permit of the damaged vessel being ligated above and below the puncture. In some cases it may be possible to suture the opening in the vessel wall. When circumstances prevent these measures being taken, the bleeding may be arrested by making firm pressure over the wound with a pad; but this procedure is liable to be followed by the formation of an aneurysm.
Minute puncture of arteries such as frequently occur in the hypodermic administration of drugs and in the use of exploring needles, are not attended with any escape of blood, chiefly because of the elastic recoil of the arterial wall; a tiny thrombus of platelets and thrombus forms at the point where the intima is punctured.
Incised Wounds.—We here refer only to such incised wounds as partly divide the vessel wall.
Longitudinal wounds show little tendency to gape, and are therefore not attended with much bleeding. They usually heal rapidly, but, like punctured wounds, are liable to be followed by the formation of an aneurysm.
When, however, the incision in the vessel wall is oblique or transverse, the retraction of the muscular coat causes the opening to gape, with the result that there is hæmorrhage, which, even in comparatively small arteries, may be so profuse as to prove dangerous. When the associated wound in the soft parts is valvular the hæmorrhage is arrested and an aneurysm may develop.
When a large arterial trunk, such as the external iliac, the femoral, the common carotid, the brachial, or the popliteal, has been partly divided, for example, in the course of an operation, the opening should be closed with sutures—arteriorrhaphy. The circulation being controlled by a tourniquet, or the artery itself occluded by a clamp, fine silk or catgut stitches are passed through the outer and middle coats after the method of Lembert, a fine, round needle being employed. The sheath of the vessel or an adjacent should be stitched over the line of suture in the vessel wall. If infection be excluded, there is little risk of thrombosis or secondary hæmorrhage; and even if thrombosis should develop at the point of suture, the artery is obstructed gradually, and the establishment of a collateral circulation takes place better than after ligation. In the case of smaller trunks, or when suture is impracticable, the artery should be tied above and below the opening, and divided between the ligatures.
Gunshot Wounds of Blood Vessels.—In the majority of cases injuries of large vessels are associated with an external wound; the profusion of the bleeding indicates the size of the damaged vessel, and the colour of the blood and the nature of the flow denote whether an artery or a vein is implicated.
When an artery is wounded a firm hæmatoma may form, with an expansile pulsation and a palpable thrill—whether such a hæmatoma remains circumscribed or becomes diffuse depends upon the density or laxity of the tissues around it. In course of time a traumatic arterial aneurysm may develop from such a hæmatoma.
When an artery and its companion vein are injured simultaneously an arterio-venous aneurysm (p. 310) may develop. This frequently takes place without the formation of a hæmatoma as the arterial blood finds its way into the vein and so does not escape into the tissues. Even if a hæmatoma forms it seldom assumes a great size. In time a swelling is recognised, with a palpable thrill and a systolic bruit, loudest at the level of the communication and accompanied by a continuous venous hum.
If leakage occurs into the tissues, the extravasated blood may occlude the vein by pressure, and the symptoms of arterial aneurysm replace those of the arterio-venous form, the systolic bruit persisting, while the venous hum disappears.
Gangrene may ensue if the blood supply is seriously interfered with, or the signs of ischæmia may develop; the muscles lose their elasticity, become hard and paralysed, and anæsthesia of the “glove” or “stocking” type, with other alterations of sensation ensue. Apart from ischæmia, reflex paralysis of motion and sensation of a transient kind may follow injury of a large vessel.
Treatment is carried out on the same lines as for similar injuries due to other causes.