Anemia

General issues

Anemia is present when the concentration of hemoglobin in the peripheral blood is below the normal range for the patient's age and sex (i.e. 14 ±2 gm/dl for women, 16±2 gm/dl for men and 12±2 gm/dl for children). When anemia is present, the red blood cell population is usually reduced. The normal red blood cell count is 4.8±0.6×106/mm3, for women and 5.4±0.9×106,/mm3 for men. The hematocrit indicates the proportion of red blood cells in the blood. Greater than 40% for men and 37% for women is considered normal. The major red blood cell indices, which may be helpful in the differential diagnosis of anemia are: the mean corpuscular volume (MCV) which is the average red blood cell size (normal is 87±5u3); the mean corpuscular hemoglobin (MCH) which is the amount of hemoglobin per cell (normal is 29±2 pg of hemoglobin/cell); and the mean corpuscular hemoglobin concentration (MCHC) which is the average concentration of hemoglobin per cell (normal is 34±2%).

These erythrocyte indices may be useful but it should be emphasized that they are averages and complete evaluation requires microscopic examination of the peripheral blood smear which will reveal evidence of red blood cell size (macrocytosis, microcytosis) and shape as well as evidence of the degree of maturity of the red blood cells (i.e. presence of reticulocytes or nucleated cells), the intensity of hemoglobin staining (hypochromia, normochromia or hyperchromia), or the presence of macrocytes, target cells, spherocytes, schistocytes or other abnormally shaped cells. In some situations, automated analysis of erythrocyte indices may reveal normal range results, but direct observation of the peripheral blood smear shows evidence of a dimorphic anemia (e.g. iron deficiency plus megaloblastic anemia) in which some cells are clearly microcytic and hypochromic and others are macrocytic, accounting for the normal indices which reflect an automated average of the two abnormalities. No analysis of anemia is complete without a direct observation of the peripheral blood smear by an experienced observer

Neurological aspects of the anemias

Non-specific neurologic effects of anemia

There are very few neurological effects of anemia per se. Headache and lightheadedness may occur in severe anemias but these symptoms usually require that the hemoglobin concentration be reduced by at least one-half. In slowly developing anemias, many patients may have little or no neurological symptoms with hemoglobin concentrations as low as one-tenth normal.