c. Infective thrombi are those distinctly due to the injurious effects of micro-organisms, and are those mainly concerned in the various manifestations of sepsis which are of interest to surgeons.
While the ordinary evidences of thrombosis are most often looked for in the veins of the extremities, in the lungs, and in the cranial sinuses, it must not be forgotten that thrombosis may occur equally easily in the portal system of vessels; in which case we find the most marked expressions in this system and in the liver. In cases also of pyemia proceeding from lesions in the rectum or in the bowels there are evidences of infection, abscess, etc., in the liver, but not in the lungs, to which point infective thrombi from other sources are promptly carried.
The ultimate fate of a thrombus depends entirely upon the presence or absence of bacteria. If septic, it invariably breaks down. If aseptic, it may undergo one or more of the following metamorphoses:
A. Decolorization.—This is noted particularly in the red thrombi, and is due to disintegration of the red corpuscles, their coloring matter being diffused and resorbed or transformed into hematoidin. It would be a mistake, however, to suppose that all light-colored thrombi are those which, originally red, have been decolorized. The possibility of white thrombi must always be remembered.
B. Organization.—This is the result of time, and means a metamorphosis into solid vascular connective tissue. Newly formed, minute, vascular loops project from the vasa vasorum into the thrombus, and it becomes thus vascularized, while the completion of the organization is due, in the main, to spindle-cell connective tissue, which is formed by wandering cells that penetrate into the thrombus from without. This gives the organized thrombus a certain resemblance to a sponge, and makes the original vein resemble a cranial sinus, since its interior is spanned by bands of connective tissue. Typical illustrations of this kind are seen, for instance, where the iliac veins join to form the inferior cava, by which a certain amount of obstruction to venous return is produced without its being total. The length of time required for these changes is indefinite. They begin, however, within a short time after ligature of a vein, and proceed with a rapidity varying according to circumstances.
C. Calcification.—Calcium salts are occasionally deposited in thrombi, usually not until they have undergone considerable contraction and alteration; as the result of which we have formation of small masses, essentially minute calculi, to which the name of phleboliths has been given. These phleboliths are not infrequently found in more or less occluded and much distended varicose veins of the extremities, and they prohibit the occurrence of softening.
D. Softening.—This is the most serious termination of the thrombotic accident, and is usually due to the agency of infecting organisms. A non-infectious form is, however, recognized, by which there is a metamorphosis of original clot into an oily or pulpy fluid, usually dark colored, but in the white thrombi often yellowish white, reminding one crudely of pus. The discovery of such material under these circumstances has led in time past to the supposition that pus, as such, was found floating in the blood—a condition that does not exist except under extraordinary circumstances. It is with infection of thrombi and consequent softening, however, that surgeons have most to deal, and the paramount importance to them of such disturbances is emphasized in the article under Pyemia.
A closely allied topic to that above considered is the subject of thrombophlebitis. This means, in effect, inflammation of one or more veins, which is directly due to the presence therein of thrombi. Such a condition is, in its strict sense, an inflammation, since it is always an infectious process. If in the veins of a non-infected region simple thrombi form, they may be occluded by organization of the included masses, but such a process never extends beyond the immediate area involved. On the other hand, if the process is essentially an infectious one, either from without or from within, then both vessel and its contained thrombi succumb completely to the infectious process, which is also essentially a spreading one; and this is limited only by mechanical barriers, by conservative suppuration, or often only by the life of the individual. Excellent examples of thrombophlebitis are seen in the involved uterine sinuses in cases of puerperal septicemia, and in the cranial sinuses after infected compound fractures, or particularly after disease originating in the middle ear has extended to them.
Thrombosis is, at times, a distinctly surgical condition, and often a surgical complication of febrile and other diseases, especially typhoid, in which it constitutes a serious complication and prolongs convalescence for a period of several months. If foreseen it can scarcely be prevented, and when present calls for treatment varying with the location of the lesion and the exciting causes. In the earlier stage anything like rude manipulation or massage is very unfortunate, since soft clots might thus be broken up and distributed to other parts of the body. Absolute physiological rest combined with the application of silver ointment, of ichthyol-mercurial ointment, which should be covered with some non-absorbent material, will probably give the best results. If the lower limbs are affected it may be well to elevate the feet so as to favor return of blood through vessels not yet obstructed. After a certain length of time the thrombi may be regarded as at least adherent if not organized, and massage will prove an important remedy, since by it the lymphatics will be better enabled to take up the fluids which have leaked from the bloodvessels and produced the edema which always characterizes these cases. Sluggishness of circulation is nearly always followed by more or less laxness of tissue, or actual hypertrophy, and a limb thus involved may never regain its original size or flexibility. Veins once compromised, if not occluded, frequently become varicose, or varicosities develop in adjoining veins and still further complicate the case. For such difficulty the measures discussed in the chapter on the Veins may be later required.
In every fresh case of thrombosis or thrombophlebitis great care should be taken in order that by no means shall the clots be disengaged and float away. The dangers correspond to those existing in variocele and nevi, often treated by the older methods of injection of coagulating material. In one instance reported, a child died within half an hour after the injection of an iron salt into a small nevus of the face. Coagulation was excited to a point far beyond the limits intended.