1. Resolution.
—The speedy subsidence of hyperemic phenomena is known as resolution—a term which has also been applied to the retrograde phenomena after a genuine inflammation. For present purposes it implies, first, the subsidence into inactivity of the exciting cause or its complete removal. This may include the passing of an emotion, the removal of an irritant, the loosening of a bandage, the resort to certain applications or to constringing or astringing measures by which the effect is counteracted. A particle of dust in the conjunctiva may within a few moments produce an active congestion of the conjunctival vessels, which, ordinarily scarcely visible, becomes prominent and easily noted. The removal of the offending substance permits a return to their original size in perhaps a half-hour. This is an example of the speedy subsidence of the hyperemia of dilatation after removal of the cause. Should the hyperemia not subside promptly, it is well to use cold applications, or in this instance an astringent collyrium, or some agent whose physiological effect it is to produce vascular contraction, as cocaine, adrenal extract, etc.
2. Acute Swelling.
—When the effusion above referred to takes place into loose connective tissues the condition is spoken of technically as edema, while when it occurs into a previously existing cavity, such as that of a joint, it is known as an effusion. The amount of blood thus effused will be influenced by the anatomical and mechanical conditions existing about the part. It may be presumed, as a general rule, that when the extra vascular pressure equals the intravascular pressure little or no more fluid may escape. As a matter of fact, it is seldom that the former rises to the degree of the latter. Conversely, one method of treating such edemas and effusions is by some device which shall make the extravascular pressure exceed the intravascular, when the fluid is, as it were, forced back into the vessels, and is made to resume its proper place within the same. This is often done by taking advantage of elastic compression, as when a rubber bandage is applied about the part. In certain parts of the body it may be done by pressure brought about by some other device. Pressure may be used for two purposes:
A. To so increase extravascular pressure as to limit the possible amount of an effusion, as when it is put on early after an injury; or,
B. When it is used as a later resort for the purpose of reducing swelling which has already occurred.
3. Chronic Swelling.
—This is something more than the swelling alluded to under Acute Swelling. Chronic swelling implies either a continuous passive hyperemia, or, what is more common, a positive increase in tissue elements as the result of an oversupply of nutrition brought by the blood, which itself was furnished to the part in a degree far in excess of its needs. The result is a more rapid reproduction of cell elements, with result in the shape of tissue thickenings or tissue enlargements, known as hypertrophy, or, more properly speaking, hyperplasia, of a part, and to the laity as “overgrowth.” This chronic swelling or chronic enlargement is in some degree also connected with the phenomena of escape of white corpuscles from the bloodvessels and mitotic division of certain tissue cells, which have up to this time been usually regarded as a feature of the true inflammatory process.
4. Gangrene.
—This may be the result of hyperemia—for the most part the passive forms—though most instances of gangrene due to intrinsic causes are inseparable from the presence of infectious microörganisms. The gangrene which is spoken of here includes that due to the pressure of tumors, tight dressings, or any natural or intrinsic agency, and that due to pressure from without when not so pronounced as to produce immediate and total loss of circulation in a part. It includes the formation of many bed-sores and so-called pressure-sores, which may be due to an enfeebled heart, to an obstructed pulmonary circulation, or to external pressure in conjunction with cardiac debility. While insisting, then, that gangrene should be recognized as a possible result of hyperemia, it may be added that it is in effect a tissue death, and that dead tissue is always and everywhere practically the same thing, no matter by what causes brought about. Consequently, the subject of gangrene will be considered under a separate heading.