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.