Gangrene is known also as necrosis, although this term is usually limited to gangrene of bone. It is known also as mortification, and to the older writers, especially when soft parts die and separate in sloughs, as sphacelus. Gangrene means death of tissue in visible and more or less circumscribed masses. It is distinguished from ulceration not on account of molecular disintegration, particle by particle, but because of death in toto and synchronously of a large, perhaps innumerable, number of cells. Gangrene is described as due to causes which may be:
A. Traumatic
, including the so-called thermal causes as essentially mechanical injuries. Under this head are included cases where injury is the primary cause, whether this injury is the crushing of a limb, the separation or occlusion of its main bloodvessels, the division of its main nerves, or the crushing or pulpefying of its entire structure by machinery or accident; also those so-called thermal cases which are due to intense heat or intense cold. To these might be added the chemical causes, comprising injuries by powerful caustics, alkalies, or acids, which are known to cause speedy death of every living tissue with which they come in contact.
Gangrene from frostbite is often of the moist type. There is scarcely a limit to its extent, either in area or depth. It is due primarily to thrombosis, which is followed by a purplish color of the skin, by loss of local warmth, and numbness. Naturally it involves the ears, nose, fingers, and toes. But after alcoholism and exposure one or more entire limbs may be involved. With moist gangrene there is danger of [septic infection] (q. v.). After formation of a line of demarcation the line of amputation may be made to follow it closely, but the best results are obtained by higher division, at points of election, where tissues are less sensitive and less infiltrated.
B. Local Causes.
—These are largely connected with ischemia. Gangrene from edema—itself the result of passive hyperemia and exudation—is not infrequent, the most common expression of this condition being seen perhaps in the external genitals of the male. Embolism due to valvular heart disease, thrombosis due usually to a preceding phlebitis, but possibly to marasmic origin, especially met with after confinement, with disturbance in the uterine sinuses, shutting off the circulation by endarteritis, which thus assumes the form obliterans, are some of the local causes which concern the bloodvessels alone. In fact, the majority of cases of spontaneous gangrene are probably due to changes in the vessels, endarteritis being the cause of a condition known as atheroma of vessels, in which fungoid outgrowths, or, rather, ingrowths into the vessel lumen, are common. Any one of these, if detached, may serve as an embolus. The degenerative excavations in the thickened walls of the bloodvessels, which discharge more or less cholesterin and other debris, and which have been known as atheromatous abscesses (misnomer), are frequently the precursors of the disease under consideration. As the result of these changes alone, without reference to formation of emboli, vessels may become completely occluded, especially when slightly injured.[2]
[2] Intermittent claudication, when recognized, may be regarded as a precursor of that arteriosclerosis which may proceed to gangrene. The term implies temporary anemia of one or more of the extremities, with numbness, burning, or prickling sensations in the skin, occasional cramps in the muscles, with loss of power, tenderness of the nerve trunks, weakening or loss of pulse in the affected part. When these symptoms occur in the feet they are not infrequently followed by terminal gangrene or other evidences of angioneurotic necrosis, including even those forms known as erythromelalgia and Raynaud’s disease. Its treatment, of course, is relaxation of vasomotor spasm, best accomplished by the use of the nitrites, among which nitroglycerin is perhaps most valuable.
Extravasation of blood is another cause connected with the bloodvessels, this coming usually from traumatic rupture, possibly from idiopathic causes. At any rate, the tension in the part may threaten its life because of the pressure which overcomes the circulation of blood. Ligation of the main trunk of an artery is sometimes followed by gangrene, no matter how carefully done, collateral circulation being insufficient to sustain the nourishment of the part. In certain fractures, simple as well as compound, the blood supply of a part is rudely broken off by injury to a bloodvessel in such a way as to cause local or general death, either of a bone or of the entire limb. Flaps made for plastic purposes, arranged without sufficient regard to their proper blood supply, or so dressed after operation as to sustain undue pressure, are often so shut off from the heart as to die for want of blood. Finally, gangrene may be the result of pressure either from splints, bandages, etc., or from tumors increasing in size, or possibly, as in certain pressure sores, etc., from the mere weight of the body. Here, too, chemical agents must be mentioned, referring now to the peculiar action of certain foods or drugs, particularly ergot. Thus antiseptic solutions, particularly carbolic acid, may be made strong enough to destroy the vitality of certain tissues. Carbolic gangrene (Warren) is a possibility not to be forgotten.
Extravasation of urine, unless promptly recognized and appropriately treated, or especially as occurring when the urine is peculiarly toxic (ammoniacal) and the patient’s vitality reduced, as in confirmed alcoholics, is almost sure to produce gangrene which may easily terminate fatally.
Fig. 14