Classification of anemias

Common mechanisms of anemias at different conditions allows to divide all significant clinical forms of anemia into several groups. The task of the physician is to find the main pathogenetic (and if possible, etiologic) factor and to administer proper treatment.

At present anemias are classified according to pathogenetic principle with the account of etiological and clinico-morphological forms.

According to modern classification there are 3 groups of anemias:

1) anemias caused by blood loss (posthemorrhagic),

2) anemias caused by disturbances of blood circulation (deficient),

3) anemias due to increased blood destruction (hemolytic). Each group is subdivided into several groups.

Posthemorrhagic anemiasare caused by the blood loss. They are caused by traumas, pathological processes, accompanied by damage of the vessel or hemorrhage from the inner organs. Depending on the size of the injured vessel and the rate of the blood loss it may be acute or chronic.

Acute anemia

This is massive hemorrhage of the vessels of the stomach and intestines in ulcer of the stomach and duodenum, from the ulcers in typhoid fever, in ectopic pregnancy, pulmonary hemorrhage in tuberculosis, rupture of aortic aneurysm.

The large is the vessel, the closer it to the heart, the more dangerous is the hemorrhage. In rupture of the aortic arch, loss of less than 1 liter of blood causes death due to sudden drop of arterial pressure. The death occurs before exsanguination of the organism, therefore anemia in the organs is not marked. In hemorrhages from small vessels, death occurs when half of the blood is lost. The patients develop the signs of hemorrhage: pale skin, oligohemia of organs, collapse signs. If the hemorrhage is not fatal, the blood loss is compensated due to regeneration processes, taking place in the tissue of the bone marrow. The bone marrow of the flat bones proliferates and becomes bright. The yellow bone marrow is replaced by red (hemopoietic) one. In repeated hemorrhages, extra-medullary hemorrhage may occur in the spleen, liver, lymphatic nodes and other organs. The prognosis of posthemorrhagic anemia depends on the rate of blood flow. Rapid blood loss of 1/4 of the total blood volume may cause shock, loss of 1/2 of the total blood volume is incompatible with the life. Loss of 3/4 of the total circulating blood does not cause death if it occurs

slowly during several days. In healthy persons, even at considerable blood loss, its composition restores in A—5 weeks, in weak ones it restores for a longer period of time.