HYPERÆMIA. CONGESTION.
Definition. Forms, active—arterial, passive—mechanical—venous. Determination of blood. Causes of active congestion. Vaso-motor nerves. Lesion of spinal cord; or of sympathetic nerve. Reflex irritation. Central cause. Physiological hyperæmia. Medicinal hyperæmia. Bacteridian (toxic) hyperæmia. Arterial obstruction. Thrombus, tumor. Cold, chill. Removal of pressure. Cardiac hypertrophy. Symptoms, bright red color, swelling, dropsy, migration of cells. Rise of local temperature. Tenderness. Altered function. Causes of passive congestion. Obstructions in the lungs, heart, veins. Diminished force of circulation from age, debility, arterial disease, distance from the heart, decubitus, vaso-motor disorder. Gravitation—hypostatic congestion. Tumors. Paresis. Symptoms. Cyanosis. Distended veins. Coldness. Transudation—watery. Hæmorrhage. Thrombus. Hyperplasia. Atrophy. Postmortem lesions. Treatment. Remove Cause. Correct injurious gravitation. Correct any fault in blood pressure. Derivation. Constringe or support part. Massage. Electricity. Improve general health.
Definition. An excess of blood in a part. It is distinguished from inflammation by the absence of that tissue reaction, which leads to or constitutes the special phenomenon of that morbid process.
Hyperæmia is divided into active or arterial and passive, mechanical or venous. A capillary form has also been described but usually capillary congestion is seen in both the arterial and venous types.
I. Active or Arterial Determination of blood. In this form the arteries are dilated under a direct nervous influence. Causes. In all the regular functions of the body, the flow of blood is under the direct control of the vaso-motor nerves which proceed from the spinal cord, through the branches of the sympathetic to be distributed with the blood vessels. The hard pulse of pleurisy is due to rigid contraction of the constrictor muscles under the action of the vaso-motor nerves, and the blush of shame is due to their relaxation. Some claim an active dilatation of the arterial muscular coats, others look more simply upon the dilatation as a mere yielding of the coats under the blood pressure, when the constrictor muscles are relaxed. This vaso-motor paresis may be induced: 1st, by any lesion of the spinal cord. 2d, by the cutting of a sympathetic trunk, that of the abdomen, for example, which leads to active congestion of the abdominal viscera, or the section of the cervical sympathetic which leads to watering of the eye, sweating, congestion, and scabbing on the corresponding half of the face. 3d, by reflex irritation through the sensory nerves, as in congestion through friction, heat or cold to the skin, or that resulting from excessive use of an organ such as the mammary gland. 4th, by causes acting directly through the brain as in emotional blushing or the facial congestion of violent rage.
Physiologically we see the operation of this nervous control in the congestion of the gums during dentition, of the salivary glands during mastication, of the stomach and bowels during digestion, of the womb during gestation, of the mammæ at parturition, and of erectile organs in copulation.
Medicinal agents act in the same way, opium or alcohol producing active dilatation, and belladonna and ergot causing active contraction of the arterial walls.
Bacteridian poisons act in the same way, tuberculin and a number of others causing active dilatation.
The obstruction of one artery by thrombus, tumor, or ligature, causes increased tension in the collateral branches coming off just above and an active congestion in the parts to which these are distributed. While this is directly due to increased local pressure, it is also an instance of the lack of balance between the blood pressure and the resistance of the vascular walls. In this case there is increase of pressure, in the other a diminished resistance.
If there is a superficial anæmia, as from cold or chill, there is of necessity, an internal hyperæmia. This contributes to the production of internal congestions and inflammations, though the seat of election of such inflammation is usually determined by the nervous sympathy between the part chilled and the deeper organ affected.
Another cause of congestion is the lessening of pressure by the parts surrounding the vessel. Thus in cupping, there is prompt cutaneous congestion, and a similar result occurs in pericardium, pleura, or peritoneum on the withdrawal of the liquid of hydropericardium, hydrothorax or ascites.
Another cause of congestion is found in hypertrophy of the heart and increased force of the blood flow (blood tension). In such cases those organs become congested in which there is some previous debility or disease of the blood vessels.
Symptoms and results. The symptoms are a bright vermillion redness, tension or swelling, heat and tenderness. Pulsation is stronger in the vessels leading into the part, secretions tend to increase but may give place to a serous effusion or hæmorrhage. The bright redness is attributed to the rapid circulation of the red globules which have not time to give up their oxygen to the tissues. It is sharply circumscribed where the affected arterioles have no free anastomosis with those of neighboring parts, diffuse where anastomosis is abundant, and when on the skin it is liable to rise in knots or buttons as in urticaria. When pressed the redness entirely disappears unlike the redness of inflammation.
The swelling may be due to the simple turgescence of the bloodvessels, but also often to transudation of serum as in and around the cow’s udder at parturition. The occasional migration of globules, and their escape through minute lacerations in the vascular walls add alike to color and turgescence.
The elevated temperature, (rising sometimes 3° C.) in the congested area, is attributed to the more active circulation, and Schiff prevented its appearance after section of the cervical sympathetic, by tying the carotid and vertebral arteries on the same side.
The tenderness of the congested parts varies inversely as the looseness of texture and the facility for swelling. It may be scarcely perceptible in the mammary region, and intense under the horn or hoof.
The functions in the congested organ are often seriously interfered with, secretions appearing in excess or entirely altered. When the congestion lasts it may cause hypertrophy, induration or hyperplasia, these are however rather sequels than lesions of the condition. Simple congestion is usually quite transient, and if prolonged, often merges into inflammation.
II. Passive or Venous Congestion. In this there is no excess of blood entering the part, but the regular supply is delayed in the veins by some obstruction, and these vessels and, later, the capillaries are gorged with black blood.
Causes. 1st, Mechanical obstruction to the onward flow of blood, as in the case of disease of the lungs hindering the flow of blood from the right heart; disease of the right heart allowing a reflux of blood into the veins; or pressure by tumors or otherwise on the great or small venous trunks. If in the heart or lungs the whole systemic venous system becomes the seat of passive congestion; if in a single venous trunk then only the parts the venous radicles of which are tributary to this. We find examples of this in phlebitis, in compression by the swellings of strangles, in the result of a bandage or ligature tied round a limb at some distance from its extremity, and in the compression of the iliac veins by a gravid womb.
2d. Diminished force of the blood current in the veins, as from old age or great debility and especially from weakness of the heart’s action. Also from disease of the arterial coats which impairs their tonicity. The force being too weak to force the blood actively through the capillaries and veins, it becomes unduly charged with carbon dioxide and other products of tissue waste, so that nutrition suffers and the walls of the capillaries lose their vital force. This condition is aggravated in the hind limbs by the distance from the heart, and the dependent position, and in decubitus by the compression of the vessels of the limbs. Also by injuries to the vaso-motor nerve supply as œdema appeared in the hind limb after tying of the femoral vein in animals the abdominal sympathetic of which had been cut, but not in animals in which this nerve was left in its normal condition (Ranvier).
3d. Gravitation in weak states of the circulation must be looked upon as a cause of venous congestion. This is seen in the examples of hypostatic congestion and œdema seen in the lungs and other internal organs in low conditions and in the advanced stages of debilitating diseases, and in certain cases of stocking of the limbs in horses.
4th. Valvular insufficiency of the left heart and tumors or aneurisms interfering with circulation through the aorta, cause passive congestion of the pulmonary veins and œdema of the lung.
5th. Tumors and diseases of the liver determine passive congestion of the portal system and ascites.
6th. Passive congestion is very liable to take place in an organ the functions of which are impaired as in a paralyzed part. In this the hyperæmia may start in the capillaries and extend to the veins or even to the arteries.
Symptoms and results. If on a mucous membrane or white skin the color becomes dark red, or violet (cyanotic) with evident distension of the capillaries and veins, the latter of which may stand out as knots or cords, there is an appearance of swelling or enlargement and sometimes coldness of the part. Soon the watery part of the blood transudes in excess, constituting dropsy, with increased swelling and pitting on pressure. On the mucous surfaces it determines an abundant serous secretion. The color is deepened by the escape from the vessels of red globules as well as white. The transudation contains little albumen and only exceptionally fibrine. In connection with the marked deoxidation and high carbonization of the blood, the nutrition of the part is largely arrested together with the functions, secretory, motor or otherwise. The imperfectly nourished vessels may give way, leading to hæmorrhage, or nutrition may be definitely arrested producing moist gangrene or ulceration. Sometimes a thrombus is formed in a congested vein. The changes in the affected organs depend much on the degree and duration of the hyperæmia. If slight and lasting it causes permanent induration and thickening, from connective tissue hyperplasia as frequently seen in the hind limbs of the horse. In case of blood transudations the altered coloring matter gives the various shades of gray, brown or black. If long continued the organ may shrink and atrophy occur from defective nutrition and contraction of the fibrous hyperplasia.
In making post mortem examinations mistakes may be made through the occurrence of changes after death. Thus a hvperæmia which was quite considerable during life may virtually disappear through the contraction of the arterial and capillary coats forcing the blood on into the veins. A minute point of extravasation here and there may be the only macroscopic lesion left. Again a marked venous and capillary hvperæmia in a dependent part of the body or of an organ may be entirely due to hypostatic conditions, the blood having settled into the lowest part of the vessels since the death of the animal. To avoid this source of error one must always carefully note the position of the carcass after death. Under other circumstances the superficial veins and capillaries may fill up with blood through the occurrence of decomposition and the evolution of gases in the internal cavities, which empty the splanchnic and parietal vessels by compression.
Treatment. The general principles of treatment may be stated thus: 1st. Remove the cause of the hyperæmia if possible, especially any mechanical cause; 2d. Secure the influence of gravitation in favor of the return of blood to the heart; though not so available in animals as in man, it is of great value in congestions of the head, ears, tail, and to a less extent of other parts; 3d. Correct any fault of blood pressure, excess or deficiency, which may act so as to cause active or passive hyperæmia; 4th. Establish derivation by cupping, leeches, fomentations, pediluvia, sinapisms, etc.; 5th. Apply cold, astringents, bandages, to empty the hyperæmic vessels, or kneading, rubbing, or electricity, to hasten the flow of blood; 6th. To improve the quality of the blood and general health, in plethora by low diet, purgatives and diuretics, in anæmic or debilitated conditions by iron, bitters, nourishing food, fresh air, sunshine and exercise.
It is especially important to check passive congestion in febrile diseases, and mechanical congestion at an early stage of its progress (Roberts).