PLETHORA. POLYÆMIA.
Definition. Transitory only. Causes, kidney disease, drinking freely, rich feeding, profuse secretion, polycythemia, hyperalbuminosa, excess of fibrine, sugar or fat. Ratio of blood to body. Variations of globules. Symptoms, general, local. Appearance of blood. Prevention. Treatment.
Definition. An excess of blood, of the blood globules, or of the albuminoids.
Formerly accorded an important place in pathology, plethora has been entirely eliminated from some recent works. The actual amount of blood varies greatly at different times, rising after a free consumption of food or drink, and falling during a period of abstinence. A healthy activity of the secretory and excretory organs secures a fair uniform average in the plenitude of the circulatory system. Moreover, large variations are not in themselves rapidly injurious. Worm-Müller and Cohnheim introduced into dogs ten to twelve per cent. of the body weight (fifty to eighty per cent. of their blood) of canine blood without inducing fatal results. More than this was fatal. In non-fatal cases a reduction to the normal standard is speedily secured.
But we cannot count on absolute immunity in all circumstances. Disease of the kidneys, or drinking water to excess, determines a surplus of water and urinary salts (serous plethora, polyæmia aquosa). In cases of rapid gain in condition from rich feeding, and above all after profuse watery secretion (diarrhœa, diuresis, perspiration), the red globules are relatively increased (plethora polycythæmica). After hearty feeding there is a large increase of albumins (plethora hyperalbuminosa). Fibrine-forming elements are apparently in excess during rheumatism, pneumonia and other acute inflammations. Sugar is in excess after a saccharine or farinaceous meal, fat in obese individuals, after consumption of fat, after injuries to the bone marrow, and after severe diseases with much destruction of albumen.
The ratio of blood to the body weight is: In birds 1: 12; in Guinea pig 1: 19; in rabbit 1: 20; in cat 1: 21; in dog 1: 17; in horse 1: 18; in sheep 1: 24; in pig 1: 26; in ox 1: 29 (Colin). As showing the variation under even different normal conditions of the system Bollinger found the blood but 2.2 per cent. of the body weight in a fat pig, whilst it was 13.5 per cent. in a draft horse. Colin found it 2.4 per cent. in the fat ox instead of the usual 3.4 per cent.
The excess of red globules and usually also of albumins is seen as a temporary condition, in lean but vigorous animals put suddenly on an abundant diet, rich in assimilable albuminoids, in working animals, put in confinement to feed, and above all in high conditioned cows after an easy parturition, when the uterine blood has been suddenly thrown on the general circulation and the emunctories have failed to establish a balance. Also in the lymphangitis occurring after a day or two of rest, in a horse that has been hard worked and heavily fed.
It should be borne in mind that the number of red globules varies considerably in the different animals. In the dog it was by weight 148.3 grammes per 1000; in the pig 105.7; in the horse 102.9; in the ox 99.71, and in the sheep 98.2 (Andral, Gavarret, Delafond). By count the horse has 5,500,000 per cubic millimeter (7,500,000, Nocard); and the dog 5,000,000.
Symptoms. Under a sudden dangerous increase of the volume or the organic elements of the blood, there are usually dulness, lassitude, dropping of the head, strong, full, hard pulse, extra force in the heart beats, thirst, elevated temperature, and redness of the visible mucous membranes. At first there is no indication of local disease, but unless relief comes by free secretion some local complication is likely to ensue. This may be epistaxis, congestion or apoplexy of the brain, parturition fever, lymphangitis, or congestion of some internal organ, etc. A drop of blood colors deeply the finger or other object, it clots firmly in three to five minutes, and shows more than usual of a buffy coat.
Treatment. As dangerous plethora is usually a very transient condition the main attention should be given to prevention, in keeping the diet low and the emunctories active in high conditioned parturient cows; in lowering the diet and securing free secretion, or in giving exercise to high fed, hard worked horses that have been laid off work; in changing only by slow gradations thin, vigorous animals to a rich diet, etc. When the danger is imminent prompt relief can be secured by the liberal abstraction of blood. Purgatives, diuretics, and restricted diet may be applied to less urgent cases.