Primary severe anemia itself influences on blood circulation, but is seldom met. Much more often secondary anemia develops at infections or illnesses of metabolism.
Healthy people use for 5-6% of blood oxygen saturation. At normal hemoglobin content the increased need for oxygen is satisfied with increase of quantity of blood passing through tissues. If the quantity of bloody cells or hemoglobin content is low, enough oxygen is provided also with the best use of the oxygen content in blood. Even when in blood there is just 25-30% of hemoglobin of norm, the organism at rest can consume 5-6% of oxygen if uses all oxygen bound to hemoglobin.
Because of the increased loading heart at anemia enlarges, at longer anemia it hypertrophies. The need of cardiac muscle for oxygen is increased; the organism cannot satisfy it because of tachycardia and disadvantage of oxygen in blood. Increase load on muscle and insufficient providing with oxygen lead to fatty degeneration of cells. Heart of the people having serious anemia is very flabby and colorless.
On x-ray films the proportional cardiomegaly and a strong pulsation is visible. The blood pressure is usually lower than normal, because of compensatory extension of small arteries.
The heart failure is seldom met. At significant deficiency of oxygen permeability of vascular wall increases there can be edemas on face and extremities. At the slightest movement the patient has a dyspnea. With stopping of anemia symptoms quickly disappear. Anemia for children is dangerous, especially at dehydration.