Definition

By congestion of the lungs is meant an undue fulness or engorgement of the pulmonary vessels with blood, and especially those concerned with respiration as distinguished from others engaged in the nutrition of the organs. It is convenient to consider this disease under two headings - A, as acute, and B, as passive or mechanical congestion. The acute form of the affection is most frequently met with in horses subjected to severe exertion and distress. In the second form it arises in the course of various forms of disease, and especially obstructive heart disease. It is also a frequent and fatal accompaniment of the specific fevers, and may complicate acute inflammation of many of the organs of the body.

Causes

Congestion of the lungs follows upon a variety of disturbances in the health of the horse.

The acute form is frequently induced by excessive exertion without previous adequate training or condition, hence the number of cases occurring among hunters and steeplechase horses pushed beyond their powers with but little previous preparation. Fat young horses fresh from grass or the hands of the dealer are particularly prone to this disorder, especially when brought into town work and made to occupy badly-ventilated and otherwise ill-conditioned stables. The same causes that produce catarrh or common cold are liable to give rise to congestion of the pulmonary vessels, and the disorder is a frequent sequel to, or complication of, inflammatory attacks affecting other organs. As a mechanical congestion it is always present more or less in obstructive diseases of the valves of the heart. Here the blood, interrupted in its course through the last-named organ, is made to accumulate in the vessels of the lungs. Passive congestion of these organs mostly arises in the course of exhausting diseases, and particularly in that form of influenza termed " typhoid".

Symptoms

In acute cases the symptoms are very urgent. Rapid but shallow breathing, "blowing" as it is called among horsemen, dilated nostrils, bloodshot eyes, head depressed and commonly held in a corner the least suitable for obtaining a supply of fresh air. The muscles quiver, the body is hot with perspiration, and the ears and legs are icy cold. Redness of the conjunctival membranes is not of that kind commonly seen in cases of acute inflammation, but of a darker colour, as might be expected in an animal whose blood is not receiving proper oxidation in the lungs. As a rule, the horse so affected persistently stands, but there are exceptions, some appearing to suffer acute pain and occasionally going down in a vain effort to obtain ease, while others, and by far the majority, become more or less dull and stupid. The heart-sounds are loud, and the pulse which is at first moderately full, becomes weak and compressible, the number being with difficulty counted owing to its rapidity and want of resistance to the touch. Auscultation yields a minute crepitating sound, besides a harsh bronchial noise in the place of the ordinary murmur of healthy respiration, and later there are areas in which the sounds are much subdued.

Cases of pulmonary congestion from excessive exertion, although exhibiting the severest distress, are more likely to recover than the so-called passive form when complicating diseases of a febrile and exhausting nature. Whether as a result of overtaxing the animal's capacity, or as a sequel to other affections, its course is rapidly fatal unless checked by treatment.

Treatment

In attempting any kind of treatment the object in view is to relieve the overtaxed pulmonary vessels of their surplus blood, and to impart tone to them and to the embarrassed and enfeebled heart. If this can be done promptly the battle is half-fought. If the hunting man is horseman enough to recognize when his mount is " pumped out", he may accomplish it by pulling up with the horse's head to the wind, slacking out the girths, hand-rubbing the legs, pulling the ears, and giving the contents of his flask to the exhausted steed. Many a horse is thus saved by a judicious rider with that intelligent sympathy which every man should have who rides to hounds. Too many do not possess it, or assume that a hired horse must be in the pink of condition and have no weakness that shall curtail the pleasure of his rider; " the last ounce", as the phrase goes, is got out of the animal by whip and spur, and he finally comes to a standstill, or a check occurs too late to save a high-spirited animal that will go till he drops. In such a situation the propriety of bleeding can hardly be called in question, but it is, comparatively speaking, a lost art among horsemen, who at one time were always ready to perform the operation with more zeal than judgment. The exhausted hunter, after first being allowed to recover himself, should be led to the nearest stable and put into the most airy box obtainable. The veterinary surgeon, when summoned, may not consider it too late to bleed, especially if the pulse is found fuller after a stimulant has been given. Every effort should be made to restore the circulation by friction, vigorous wisping of the body with straw, chafing the legs and ears, bandaging, and clothing. Alcoholic stimulants, such as gin or whisky, are mostly obtainable without much delay, and should be given at once or as soon as the animal has recovered his " wind ". Some authorities recommend carbonate of ammonia with digitalis, for which they claim the double advantage of increasing the power and diminishing the number of the heart's contractions. The doses, whether of alcohol or other chosen agents, should be moderate in amount and repeated hourly so long as symptoms of distress continue.

There is a general consensus of opinion in favour of the application of mustard to the sides of the chest, although a few dissentients of unquestionable authority have thrown doubts upon the propriety of counter-irritation. The practice appears to have very marked and rapidly beneficial effects in many cases, and in our judgment should be promptly resorted to, but hot water may be substituted where any special objection against mustard or strong liniments presents itself. The convalescent should receive unremitting care, as there is much tendency to recurrence, as also a danger of pneumonia following the attack. Besides the importance of pure air and comfortable conditions generally, the state of the bowels must be made a matter of attention, and if a tendency to constipation exists which a laxative diet is not sufficient to overcome, a small dose or two of linseed or castor oil or sulphate of magnesia may be given, but in no case should aloes or any drastic cathartic be employed.

Post-Mortem Appearances

Examination of an animal that has died of this disease shows the lungs to be very dark in colour; they are, nevertheless, compressible, and do not exhibit that solid condition and friable texture common in inflammation of the lungs. Where the overcharged vessels have given way, blackish red patches of lung are seen here and there infiltrated with escaped blood.