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).