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.