A system of practical medicine. By American authors. Vol. 1

by Unknown

If the patient outlives these more mechanical results of embolism, the local changes taking place are those tending to remove the extravasated blood or the dead tissues. The embolus has become an obstructing thrombus, and its removal is accomplished in the manner already stated in connection with the subject of thrombosis. The wedge-shaped nodule of hemorrhagic infarction becomes decolorized through the absorption, in part, of the blood-pigment. That portion which is not absorbed remains at the site of the original lesion as granular or crystalline blood-pigment. A granulation-tissue is formed at the periphery, which extends into the infarcted region, very much as the endothelial and vascularized growth extends into a thrombus. Eventually, a patch of cicatricial tissue remains as the sole indication of the previous disturbance. This termination is rather suggested for the hemorrhagic infarctions of the lungs. The results are more apparent and more easily demonstrated in the case of the anæmic necroses, and the somewhat irregular depressions with wedge-shaped scars, seen upon the surface of the spleen or kidneys, call attention to the probable nature of the process giving rise to these results. A source of embolism must also be associated, that these scars may be regarded as of embolic origin. The embolic softenings of the brain are likewise represented in after years by losses of substance. The superficial, yellow patches or localized oedematous blebs, with corresponding atrophy of the convolutions beneath, call attention to a nutritive disturbance, as do cyst-like cavities in the deeper parts of the brain. Here, too, a source of embolism must be found, that the local destruction of tissue may be attributed to embolic obstruction of vascular territories.

When the embolus arises from a septic thrombus, the results differ from those above described. The embolus then carries not only mechanical possibilities, but also a virulent action. The latter is manifested by the rapid production of local inflammatory disturbances, as circumscribed abscesses and gangrenous destruction of tissue. Since emboli are frequently lodged near the surfaces of organs, a septic pleurisy, pericarditis, or peritonitis is the usual result of the dissemination of the virus contained in the embolus. This virus is similar in character to that found in septic softening of the thrombus, and, like it, is intimately connected with the presence of microbia. Whether the latter are specific in character, as maintained by Klebs and others, or whether they are to be included among those associated with putrefactive processes, still remains an open question.

The symptoms of thrombosis obviously depend upon the resulting obstruction to the circulation of blood, and in the case of primitive thrombi are gradual in their occurrence. The degree of mechanical obstruction is determined by the nature of the thrombus, whether parietal or obstructing, and by that of the vessel, whether provided with anastomoses sufficient to permit a compensatory collateral circulation or not. In the former case, if the thrombus is small and deep-seated, there may be no symptoms to indicate its presence. When the collateral circulation is insufficient to remove the blood from a region whose efferent venous trunk is completely filled with a thrombus, the phenomena of stagnation are produced. The part becomes oedematous, and red blood-corpuscles escape from the distended vessel. If the obstructed vein is superficial, the seat of the thrombus is indicated by the resistance and sensitiveness of the part. Characteristic disturbances of function are associated with thrombosis of the various organs of the body. If the cerebral sinuses are affected, mental disturbances arise; if a cardiac thrombosis is present, it is frequently accompanied by irregularity and feebleness of the heart. When the portal and renal veins are obstructed, functional disturbances arise in the parts from which they receive their blood.

The symptoms of embolism, like those of arterial thrombosis, are primarily due to anæmia. Suddenness is their characteristic in embolism, while they are gradual and progressive in the case of thrombosis. An embolic anæmia is complete or incomplete according to the terminal or anastomosing character of the obstructed vessel. The effect of the anæmia is to stop or check the function of the part, and varies according to the size and situation of the vessel. Hemiplegia, or perhaps aphasia or other evidence of localized disturbance, follows central embolism; angina pectoris, with a disturbed cardiac action, results from embolism of the coronary artery. Sudden suffocative symptoms, with open air-passages, suggest embolism of the larger branches of the pulmonary artery. A considerable hæmaturia often excites suspicion of an embolism of the renal artery, the hemorrhage coming from the vessels in the neighborhood of the obstructed region. Embolism of a large artery of an extremity is often localized by the sensation of a blow at the part, to be followed by absent pulsation, pallor, and coldness of the region beyond the place of obstruction.

The symptoms of the subsequent effects of thrombosis and embolism are to be inferred from what has already been stated with regard to the nature of the possible lesions. To enter into their detailed consideration would demand more space than is permitted, and would modify an established sequence or necessitate a repetition, which is undesirable in a systematic treatise.

Effusions.

The various fluids of the body are derived from without, and admitted into the blood-vessels. The physiological transudation through the walls of these vessels, in the main modified serum, becomes lymph as it appears in the several lymph-spaces. From the latter the transuded fluid either returns through the lymph-vessels to the blood-current or makes its appearance upon surfaces as secretions. These are variously modified as they pass through the specific cells of glands or as they are met with in the several closed cavities of the body.

The transudations thus occurring may vary in quantity within certain limits, the latter being somewhat indefinite, owing to the difficulties in the way of exactly measuring the fluid transuded. The greater part of this transudation is represented by the quantity of lymph flowing through the main lymph-trunk, and of the secretion from the glandular surfaces of a given region of the body; but that transuded fluid is not included which may return to the blood-vessels without being carried into the general lymph-current or secreted from a gland. Such a direct return may be considered to take place whenever the pressure upon the outside of the vessel wall is greater than that within the latter, or when the chemical composition of the fluids on the two sides of the filter permits endosmosis as well as exosmosis. This varying relation in the direction of the current through the vessel wall is likely to be of frequent, if not constant, occurrence in connection with the physiological processes taking place throughout the body.

The undue accumulation of the transudation in the various closed cavities of the body is known as dropsy, and the fluid present is regarded as an effusion or an exudation. These terms are often applied somewhat vaguely, now being used as synonymous, again as representing different conditions of the transudation, which are attributed to the varying conditions of its accumulation.

Exudation is more generally used when an inflammatory process is the cause of the increased transudation, while effusion is more strictly associated with causes other than inflammatory. In the present consideration this etiological distinction will be maintained.