are classified by etiology. The causes include:
•Blood loss
•Deficient erythropoiesis
•Excessive hemolysis
Blood Loss
Anemias can result from acute or chronic blood loss. Identification of the cause of the blood loss and resolution of the loss will most likely resolve the anemia. The lost erythrocyte mass and hemoglobin content will be replaced via transfusion or erythropoiesis (Blackwell, 2001).
Deficient Erythropoiesis
Anemias due to a deficient erythropoiesis include microcytic anemias, normochromic-normocytic anemias and macrocytic anemias. All of these anemias are characterized by low hemoglobins and hematocrits (Blackwell, 2001). The distinction is made by examining the MCV (Coulter, 1991). This test provides the average size of the patient’s red blood cell. In microcytic anemias the heme or globin synthesis is deficient or defective resulting in a lower than normal MCV. In normocytic anemia the bone marrow failure prevents the erythroid mass from expanding as needed, but the volume is normal, so the MCV is normal. Megaloblastic erythropoiesis results when DNA or RNA synthesis is impaired. The MCV then exceeds normal values (Blackwell, 2001). Other tests used to evaluate erythropoiesis include reticulocyte count, red blood cell count, erythrocyte count and red blood cell width (RDW).
Excessive Hemolysis
Anemia due to destruction of RBC is much less common and rarely associated with blood loss or bone marrow failure. These anemias are caused by defects that are either extrinsic or intrinsic to the RBC. For example, an anemia with extrinsic defects is autoimmune hemolysis. An anemia with intrinsic defects is sickle cell disease.
Categories of Nutritional Anemias
Nutritional anemias are categorized using red blood cell indices quantifying the size, weight and hemoglobin concentration of red blood cells. These tests are used to categorize anemias. Table 6 categorizes nutritional anemias by red blood cell indices.
The four types of nutritional anemias are:
•Iron Deficiency Anemia
•Megaloblastic Anemia
•Pernicious Anemia
•Anemia of Chronic and Inflammatory Diseases
Iron Deficiency Anemia
Iron deficiency anemia is most commonly seen in children with low iron intakes. However, approximately 20 percent of women, 50 percent of pregnant women, and 3 percent of men are iron deficient. The DRI for iron for adult males and females 51 years and older is 8 mg/d. For females under the age of 50, the DRI is 18 mg/d. The NHANES data reports that median intakes of iron for adults aged 40 to 59 and 60 years and older are 15.5 mg/day and 14.8 mg/d respectively (Ervin, 2004).
Iron deficiency anemia may be the result of a chronic blood loss, after an acute blood loss, deficient diet, malabsorption of iron or increased need for iron. Decreased stomach acidity, due to overconsumption of antacids, ingestion of alkaline clay, achlorhydria, partial gastrectomy or weight loss surgery may lead to impaired iron absorption and ultimately iron deficiency anemia.
Clinical signs and symptoms include inflammation of the tongue, lips or mucous membranes of the mouth and spooned nails. In its advanced state, it is described as a microcytic hypochromic anemia. Laboratory tests used to diagnose iron deficiency anemia include a low hemoglobin, low hematocrit, low MCV, low serum iron, elevated total iron binding capacity (TIBC), low reticulocyte count, low ferritin, elevated RDW and elevated erythrocyte sedimentation rate. Not all of these tests may be available due to cost restraint. The MCV is the key test to examine once a low hemoglobin and low hematocrit are identified.
Once underlying causes of iron deficiency anemia are identified and addressed, oral iron therapy is preferred, however a multivitamin may be better tolerated. Absorption is best on an empty stomach, but may cause gastric upset (Blackwell, 2001). Remember that the goal of pharmacological intervention is to increase the deficient body components while avoiding a negative impact on the total dietary intake of the patient.
Anemia of chronic and inflammatory diseases
Anemia of chronic and inflammatory diseases develops as a result of an extended infection or inflammation. The anemia usually manifests itself in a similar manner to iron deficiency anemia. While the physical signs and symptoms are the same as iron deficiency, anemia of chronic and inflammatory diseases is a normochromic-normocytic anemia. In anemia of chronic and inflammatory diseases, the lab results are below normal ranges for hemoglobin, hematocrit, serum iron and TIBC. However, the MCV and ferritin are usually normal. The changes in lab test
Table 6. Anemias According to RBC Indices
| Normocytic1, Normochromic2, Anemia •Iron Deficiency (early stages) •Anemia of Chronic and Inflammatory Diseases •Acute Blood Loss •Pernicious Anemia ( about 40% of cases) | |
| Microcytic3, Hypochromic4 Anemia •Iron Deficiency (advanced) | |
| Microcytic3 Normochromic1 Anemia • Renal Disease due to loss of erythropoietin | |
| Macrocytic5, Normochromic1 Anemia •Vitamin B12 / Pernicious Anemia •Folic Acid Deficiency/Megaloblastic Anemia |
Key:
1 Normocytic - normal RBC size
2 Normochromic - normal color (normal hemoglobin content)
3 Microcytic - smaller than normal RBC size
4 Hypochromic - less than normal color (
5 Macrocytic - larger than normal RBC size
results are either related to redistribution of iron stores or impaired utilization. A multivitamin supplement with iron or oral iron therapy may be ordered, however, should be carefully monitored for expected outcomes. In cases of true anemia of chronic and inflammatory diseases, the lab values will not improve until the underlying condition resolves.
Other
