Anemia is a decrease in normal number of red blood cells (RBCs) and/or less than the normal quantity of hemoglobin in the blood.
The three main classes of anemia include:
- excessive blood loss (acutely such as a hemorrhage or chronically through low-volume loss),
- excessive blood cell destruction (hemolysis)
- deficient red blood cell production (ineffective hematopoiesis).
More specifically, it is the concentration of hemoglobin, red blood cell volume, or red blood cell number.
Sometimes, decreased blood volume (hypovolemia) is also included in anemia definition, which, however, in case of hypovolemia caused by bleeding, indirectly causes decreased hemoglobin concentration because of shift of interstitial fluid to plasma in autoreperfusion. Still, other causes of hypovolemia, such as dehydration or vomiting, which not cause loss of red blood cells or hemoglobin, actually increase blood hemoglobin concentration, which is contrary to the general definition of anemia.
Anemia is generally strictly distinguished from hypoxemia, defined as decreased partial pressure of oxygen in blood, although both conditions are causes of hypoxia.
Signs and symptoms
Main symptoms that may appear in anemia.
Anemia goes undetected in many people, and symptoms can be small and vague. The signs and symptoms can be related to the anaemia itself, or the underlying cause.
Most commonly, people with anemia report non-specific symptoms of a feeling of weakness, or fatigue, general malaise and sometimes poor concentration. They may also report shortness of breath, dyspnea, on exertion. In very severe anaemia, the body may compensate for the lack of oxygen carrying capability of the blood by increasing cardiac output. The patient may have symptoms related to this, such as palpitations, angina (if preexisting heart disease is present), intermittent claudication of the legs, and symptoms of heart failure.
On examination, the signs exhibited may include pallor (pale skin, mucosal linings and nail beds) but this is not a reliable sign. There may be signs of specific causes of anaemia, eg koilonychia (in iron deficiency), jaundice (when anaemia results from abnormal break down of red blood cells - in haemolytic anaemia), bone deformities (found in thalassaemia major) or leg ulcers (seen in sickle cell disease).
In severe anaemia, there may be signs of a hyperdynamic circulation: a fast heart rate (tachycardia), flow murmurs, and cardiac enlargement. There may be signs of heart failure.
Pica, the consumption of non-food based items such as dirt, paper, wax, grass, ice, and hair, may be a symptom of iron deficiency, although it occurs often in those who have normal levels of hemoglobin.
Chronic anemia may result in behavioral disturbances in children as a direct result of impaired neurological development in infants, and reduced scholastic performance in children of school age.
Restless legs syndrome is more common in those with iron deficiency anemia.
Anemia After Complicated Myocardial Infarction Worsens Outcome 2009..