ACUTE CONGESTION OF THE LUNGS. PULMONARY HYPERÆMIA.
Active and passive congestions. Congestion of incipient pneumonia. Congestion of over-exertion. Causes, lack of condition, fat, plethora, gorged stomach, hot weather, cold rains, cold baths, infectious diseases. Symptoms, dilated nostrils, labored breathing, deep lifting of flanks, panting, pendent head, staring, fixed, bloodshot eyes, pale—later dark red nasal mucosa, rapid pulse, palpitating heart, fine crepitation, cold limbs, tremors, perspiration, obstinate standing, till unable, blood from nose. Fulminant cases. Exposure cases. Course. Termination. Resolution. Lesions, lungs black, gorged, do not crepitate nor collapse, lessened buoyancy, cut surface, compressed bronchioles and alveoli, right heart and veins gorged, blood black, semi-liquid, petechiæ. Nature. Not yet inflammatory, blood engorgement, no cell proliferation, migration, non-exudation, pulmonary vaso-motor paresis, effect of blood pressure, of peptones, etc., of exhaustion. Treatment, relieve respiratory muscles, derivation to surface, stimulants, hot pediluvia and packs, relief of vascular system, bleeding, heart stimulants, digitalis.
Congestion of the lungs occurs in all animals as the precursor of inflammation, but as death may occur without the supervention of actual inflammation a special notice appears to be demanded. The hyperæmia of the lungs may be seen in two forms, active and passive, the latter form being secondary to other diseases, such as valvular diseases of the left heart, by reason of which the blood is forced back on the lungs and creates mechanical congestion. The active form is a pathological process developed in the lung itself, and which often proves fatal through arrest of the circulation through this organ.
Causes. The pulmonary congestions preceding pneumonia are due to the same causes with that disease. The most typical, acute and deadly form of pulmonary congestion is usually due to over-exertion in an animal that is fat and out of condition. The English hunting field presents the most typical specimens. A horse that has just left the dealer’s hands, or that is plethoric, fat, soft and flabby, is ridden over a heavy country, and though he may perform well for a few miles, he soon hangs heavily on the bit, slackens his pace, and if not pulled up, staggers and falls “all of a heap.” A farm horse, taken from grass or other soft feeding, and entirely out of condition often suffers in the same way, in going perhaps for the veterinarian in case of urgent colic in one of its fellows. Cruzel draws attention to similar congestions from over-exertion in fat cattle, and Trasbot in wild stags and hogs when beechnuts and acorns were abundant, in pampered family horses and in plethoric farm animals generally. Excessive heat (heat apoplexy) is invoked as a cause, and the arrest of hæmatosis and consequent stagnation in the pulmonary capillaries are undoubtedly accessory causes, yet the majority of cases, and the most typical and fatal, occur in the winter season (the hunting season). On the other hand, chills from rains or cold draughts, especially when heated and exhausted, are common causes, and the disease often comes on more gradually, attaining its acme after five or six hours. A horse perspiring after a hard drive and left to face a cold blast unblanketed, or one plunged by accident into ice cold water for ten minutes (Trasbot) are examples of this kind. These cases are ushered in by violent rigors, whereas in those due to over-exertion this is much less marked and is usually only suggested by the coldness of surface and extremities. Another condition which contributes to pulmonary congestion is a full stomach. The plentitude of the abdominal organs leads to compression of the lungs and hampered circulation, and when to this is added over-exertion and exhaustion acute congestion is speedily induced.
Acute congestions are noticed as an accompaniment of other diseases, but these are mostly either the localization in the lung of a specific morbid process (anthrax, influenza, distemper, strangles), or it is due to auto-poisoning, as when the cutaneous transpiration is suppressed by a coating of glue, or to embolism.
Symptoms. In the horse which fails under severe exertion there are the dilated nostrils, the labored breathing, the deep, almost convulsive action of the flanks, the hanging on the reins, the slacking of the pace, the unsteadiness of gait, and lastly the fall. There may now be noticed the protruded bloodshot eyes, the agonized expression of countenance, the extended head, the pallor, and later the blueness of the nasal mucous membrane, the short, panting breathing, accompanied by a roaring noise alike in inspiration and expiration, and the small, weak, rapid pulse often imperceptible at the jaw. If the animal has been stopped short of having fallen, or if he is able to get upon his feet, he stands with his limbs apart to secure his stability, and with the elbows turned out to facilitate the expansion of the chest. As the breathing becomes panting the respirations are less deep, the ribs are maintained permanently drawn outward, and the flanks rise and fall to a limited extent only but with great rapidity (eighty to one hundred per minute). Auscultation may detect at first an increase in the pitch of the respiratory murmur, and the presence of the finest possible crepitation sound. Soon the murmur decreases uniformly. The extremities are cold, and in this coldness the general surface to some extent participates even though it may be covered by perspiration. Tremors or rigors are present. The heart is felt behind the left elbow to beat tumultuously. If blood is drawn it flows in a thin, black, tary stream.
In some cases blood more or less frothy is discharged from the nostrils as the result of rupture of pulmonary vessels.
In the fulminant cases in cattle respiration is rapid, even panting, wheezing, the expiration attended by a hoarse grunt, sometimes nasal hemorrhage, great prostration, profuse perspiration, a stupor sets in and the animal falls and dies, with more or less struggling.
In the cases which develop more slowly, and as the result of cold and chill whether in horses or cattle, there is dullness, anorexia, prostration, increasing rapidity and oppression of the breathing, a small, frequent, hoarse cough, and at first distinct pallor of the conjunctiva and pituitary mucosa, with more or less trembling. The head is extended on the neck, toward an open door or window, if available, until prostration and stupor forbid. The pulse is small, thready, often almost imperceptible and much accelerated, while the heart beats are strong, violent, tumultuous. For a time the respiration may be not more than double the normal rythm, but it tends to more or less rapid increase with wheezing or stertorous sounds and shaken by trembling of the respiratory muscles. The nasal discharge is slight and grayish often with streaks of blood. If it increases the cough becomes looser and softer. Quite early the respiratory murmur decreases over the whole lung and a blowing sound from the bronchia or larnyx is heard on the upper middle third of the chest. This may be complicated by a mucous râle, or when hæmorrhage has supervened by a loud rattling. Percussion shows a lack of resonance over the whole lung, not so flat and definitely circumscribed as in pneumonia but a partial flatness of sound over the whole chest. In pneumonia a limited area of lung is absolutely solidified (hepatized) while the remaining lung is practically normal, whereas in acute congestion often the whole lung is gorged with blood but for some time no part of it is entirely divested of air.
Another marked feature is the maintenance at first of the normal temperature with only a slight rise of about 1°. This serves to distinguish congestion of the lungs from sunstroke (heat anhæmatosis) in which the temperature usually rises to 108° or 110° F or higher. The temperature rises however as the disease advances and merges into pneumonia. Another distinguishing feature from sunstroke is the early pallor of the mucous membranes which in heat apoplexy are strongly congested. In congestion they become dark red only with the advance of the disease and the advent of asphyxia. These features serve also to distinguish acute pulmonary congestion from contagious fevers, pneumonia and other inflammations of internal organs.
Course. Termination. The more acute (fulminant) forms are promptly fatal. In the exhausted system the lungs have become uniformly gorged with blood, which can no longer be forced through the capillaries by the right heart, the heart in turn is overdistended with blood and ceases to beat and death ensues in a few minutes.
In the less acute cases the patient survives twenty-four hours and upward, the whole lung not being equally implicated but only certain lobules, usually the lower, or the congestion, if uniform in all the lung, being less extreme.
In favorable cases recovery takes place in one or two days. There is a return of life and appetite, a gradual improvement in pulse and breathing, the respirations becoming deeper and longer, and in a few hours all the more violent symptoms may have disappeared. With a more gradual improvement recovery may still be complete in four or five days.
Lesions. When the subject has died suddenly the appearances are essentially those of uniform engorgement of the pulmonary capillaries with blood. The general aspect is a dark red, varying from reddish brown to black, the darkest shades corresponding to circumscribed areas of actual hæmorrhage. In the worst cases the whole mass may appear like black currant jelly. The lungs do not collapse when the chest is opened, they are more or less friable at various points, and different portions will sink or float in (not on) water, according as it may be more or less airless. A dark liquid blood exudes freely from the torn or cut surface. Sections of the lung tissue hardened and examined under the microscope show the alveoli and bronchioles devoid of exudate, but having their cavities compressed and obliterated by the pressure of the swollen mucosa, and its investing blood clot. The heart is overdistended with fluid blood. In asphyxiated cases the general venous system is filled with black, liquid blood, and the serosæ spotted with petechiæ.
Nature. The nature of this disease is variously understood. It differs from inflammation in the absence of active cell proliferation, and migrations of inflammatory exudation, and of fever at all proportionate to the extent of the lesions. All these may and do supervene if the patient survives but they are practically absent for a length of time at the outset. Some attribute it to paresis of the vaso-motor centres for the lungs, as the result of their over stimulation and of the retrocession of blood from the chilled surface to the internal organs. But congestions caused by cutting the cervical branch of the sympathetic nerve or the sciatic plexus are not marked by a similar blood extravasation and destruction of tissue. The delicate structure of the lung tissue and the comparative absence of mechanical support will account for this in part, the great force of the circulation overloading the capillaries, under the impulse of the heart so closely adjacent, has doubtless a certain effect, and the venous nature of the blood thus forced into the lungs and calculated to arrest all normal function has a potent influence. If we add to this, for the over-exertion cases, the sudden advent into the circulatory stream of unchanged peptones and other ingredients of the portal blood of highly fed and plethoric animals we find a sufficiently pathogenic combination. In all acute cases however the adiposity, poor condition and susceptibility to speedy exhaustion must be given their full share of responsibility.
Treatment. Girths, saddles and anything else that may hamper the movement of the chest must be at once removed and the horse’s head turned to the wind, an active stimulant given and the legs well rubbed and loosely flannel bandaged. The nature of the stimulant is of less consequence than its prompt administration. Two ounces of chloroform, of sulphuric ether, or of sweet spirits of nitre; half a pint of whisky, brandy or gin; or a pint of any of the more stimulating wines may be given, diluted in warm water so as to remove their irritating qualities. A drink of warm gruel will often go far to restore warmth to the surface and to unload the overtaxed lungs. Frequent large injections of warm water have a similar effect. Active hand rubbing of the legs and the wrapping of them loosely in flannel bandages previously warmed at the fire is equally valuable. If a roomy, well ventilated, loose box can be obtained the horse should be led to it gently and a light but warm rug placed upon the body. Valuable derivation may be obtained from pediluvia, the feet and legs up to the knees and hocks being put in buckets of water as hot as the hands can bear, and at the same time actively rubbed. If this is impossible the legs may be wrapped in bandages and wet with hot water every few minutes. Or this soothing derivative agent may be applied as well to the surface of the chest. A blanket wrung out of hot (nearly boiling) water until it no longer drops is wrapped round the body and covered up with two or three dry rugs. A second smaller rug is wrung and placed on the neck and covered by a sufficiency of hoods to keep in the heat. The legs are meanwhile hand rubbed and bandaged and the other measures above recommended carried out to restore the circulation in the surface and extremities. The time honored practice of bleeding freely from the jugular vein is one of the most effective means of relieving the overcharged heart and lungs, and should be resorted to at the earliest possible moment. The blood will at first flow in a small, dark stream, but as the circulation obtains relief the jet will increase in volume and the general symptoms will improve. From four to six quarts may be taken with advantage from an ordinary horse. This is not a pneumonia but an overloaded heart and lungs, threatening speedy death and which the abstraction of blood promptly relieves.
The longer the bleeding is delayed the less effective it is. It should not supersede the other measures already recommended. There is no real paradox in both bleeding and giving stimulants in such a case, as the essential condition is one of weakness, and if the abstraction of blood has been of use in relieving the clogged heart and lungs, the depression under which these have labored may be still further overcome by agents calculated to rouse their suspended vitality.
Trasbot strongly recommends large doses of tartar emetic and iodide of potassium to reduce the blood pressure in the lungs, an advice which will be received with hesitation by those who dread the already paretic condition of the heart. His combination of iodide of potassium with digitalis will be more confidently resorted to. One drachm of the former may be given with a half drachm of the latter twice daily.
With the advent of marked fever and other signs of pneumonia, the treatment for that disease should be resorted to.