Text book of veterinary medicine, Volume 1 (of 5)

by James Law

Hydrothorax or water in the chest is common to all domestic animals. It is as we have seen one of the most ordinary results of pleurisy, and may persist long after that disease has disappeared. It likewise occurs independently of inflammation as a dropsical effusion. Thus when the return of blood by the bronchial, pulmonary or intercostal veins, is hindered by any cause such as tumors in the bronchial glands or subvertebral region a passive effusion may take place through the coats of the vessels. In imperfection of the mitral valves the regurgitation of blood in the pulmonary veins during each cardiac systole equally causes such transudation. Chronic disease of the kidneys (Bright’s disease) with the retention of effete and injurious materials in the blood leads to dropsy of the chest as in other parts of the body. Again in many debilitated conditions parasitic and otherwise, with a tendency to general dropsy the chest participates and a collection of fluid takes place in the pleuræ.

The nature of the contained fluid will vary according to the conditions in which it has been effused. If the result of inflammation there are the different stages already indicated: first, of a yellow citrine color or red from contained blood; second, grayish and muddy either from contained pus or other changes taking place in the fluid; and third, clear limpid and translucent as seen in the later stages. If merely a dropsical effusion the fluid is watery clear and translucent or with a slight straw color. The inflammatory effusion contains fibrine or fibrinogenous elements, is associated with the formation of false membranes, and though it may remain fluid so long as it is retained in the chest, it coagulates rapidly when withdrawn. The dropsical effusion rarely contains fibrine, and then only in very small amount, and it does not coagulate when drawn off from the chest. The inflammatory effusion usually contains a greater proportion of common salt, phosphates or albumen than exist in the blood, and floating granules, particles and cell forms, none of which conditions characterize the dropsical effusions. The most prominent feature of the inflammatory effusions is thus seen to be their power of coagulation, by virtue of the contained fibrine, when exposed to the air.

Symptoms. When a sequel of pleurisy it is manifested by the symptoms already mentioned under that head as indicating the occurrence of effusion.

The dropsical cases may come on rapidly and present all the signs of troubled respiration together with the results of auscultation and percussion that characterize rapid inflammatory effusion but without the fever and acute symptoms of pleurisy. More usually it comes on insidiously, the lung accommodates itself to the gradual increase of the fluid and it is only when the accumulation has become excessive that the symptoms become prominent. In heart or kidney disease the filling of the legs and infiltrations of the eyelids and of the skin beneath the chest and abdomen are precursors or early concomitants of the disease, but in all cases the accumulation in the chest is to be measured by the height of the line of dulness on percussion and the extent of chest surface giving forth no respiratory murmur on auscultation. As the liquid rises on both sides of the chest, as it always does in such cases in the horse, the breathing becomes short and labored, being chiefly effected by the action of the diaphragm and the flanks—the ribs moving only slightly. The nostrils are widely dilated with each breath. The previously existing want of vigor and energy, the weak pulse, the poor appetite and the pallor of the mucous membranes become aggravated; the animal becomes very weak and prostrate, the loins insensible, the permanently tucked up flanks labor tumultuously, the loins rise in inspiration, the face is pinched and haggard, the eyeballs glazed and protruding, and death is preceded by the same general symptoms as in rapid effusion after pleurisy. A prominent feature of this, as of all dropsical affections, and one usually seen in the hydrothorax of inflammation as well, is the ease with which, even at an early stage of the disease, the long hairs of the mane and tail may be pulled out. In many cases they come out in handfulls when the comb or the fingers are passed through them.

Treatment. The treatment must be of the actively diuretic kind recommended for the effusion of pleurisy. It is modified however in one respect. The inflammatory action having subsided or nearly so and the condition being now essentially one of weakness a free use of tonics is demanded. Many a patient dies in such circumstances from the actively depletive treatment to which it has been subjected and the want of attention to its need of generous diet and other support. The agents prescribed for the advanced stage of pleurisy may be given, or the digitalis or other diuretics and bitters may be combined with iodide of potassium in one or two drachm doses, the amount being apportioned to the strength of the animal. Iron in the form of sulphate, perchloride or iodide may be freely given combined with gentian, quassia, or other vegetable tonic, and above all a liberal and easily digested diet must be allowed. Good will sometimes result from repeated applications of strong iodine ointment to the sides with active friction.

When the condition is dependent on disease of the heart, kidney or other organ, these must be attended to according to their special requirements.

Disconnected from such complications hydrothorax will often give way to an active treatment similar to that indicated above. In some cases however our only hope of even temporarily prolonging life lies in the operation for drawing off the fluid.

Tapping the chest or as it is technically called thoracentesis or paracentesis thoracis has proved sufficiently successful in the lower animals to warrant its continuance in cases that resist other modes of treatment. It is highly probable that the larger proportion of unsuccessful cases is due in great part to the hopelessly advanced stage at which it is often had resort to, to the insufficient precautions adopted in its performance, and to the want of appropriate dietetic and medicinal treatment. Dr. Bowditch’s treatment by paracentesis saved in the human subject at the rate of about two patients in five and we ought by availing of similar precautions to reach the same standard.

The cannula employed in veterinary practice is a silver tube two inches in length, a quarter of an inch in diameter and furnished with a shield of the same metal at one end. The trochar by which it is introduced is of steel or brass. To carry out Dr. Bowditch’s system the operator must supply himself with a syringe of a somewhat smaller bore and an intermediate brass piece of a size adapted to fit accurately into the cannula and supplied with a stopcock. By an instrument of this kind the fluid can be drawn off by means of the syringe without any risk of the introduction of ærial germs which always tend to induce suppuration and even a putrefactive decomposition in the contained fluid.

The point selected to operate on is, in the horse, ox or dog, in front of the anterior border of the ninth rib, at its lower end or close to its union with the cartilage. The point of the trochar should be directed slightly upward and forward to avoid the possibility of injuring the diaphragm. The skin is first rendered aseptic by shaving, followed by a thorough soapy wash and a free use of mercuric chloride solution (1:500). It is then pricked with a lancet, then drawn aside that the wounds in the skin and muscles may not correspond after the cannula has been withdrawn. The trochar is then pushed steadily through the intercostal space till all obstruction has been overcome, when it may be concluded that the pleural sac has been reached. The trochar is now withdrawn and the fluid allowed to flow from the cannula until there is presumably some risk of the introduction of air, when the brass piece is to be applied and the remainder drawn off with the syringe or aspirator. As a substitute for the aspirator a caoutchouc tube, eighteen inches long, put on the cannula or needle and having its lower end plunged in a solution of boric acid will prevent the entrance of germs. A prob has often to be introduced to prevent plugging of the cannula by floating false membranes, and a new puncture in a different place may be necessary. In the case of excessive accumulation it is often advisable to draw it off at two operations, as recommended in large abscess of the pleura and for the same reasons. The need for such a precaution will be understood when it is stated that in bad cases the chest contains as much as six or seven ordinary stable bucketfuls of the liquid. If, however, it is limited in amount it may be all withdrawn at once.