Disease Essay

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e-Therapeutics+ : Therapeutics : Blood …

Blood Disorders: Common Anemias
Date Prepared: April 2007 S. Rutledge Harding, MD, FRCPC Anemia is typically defined as a hemoglobin (Hgb) value that is two standard deviations below the mean, according to sex, age and, sometimes, race. This defines the lower limit of the normal range provided by most clinical laboratories with their patient reports. Recently, arguments have been advanced to establish optimal rather than statistical lower limits of Hgb, especially in older adults, based on morbidity and mortality data.1 Optimal Hgb concentrations were found to be 130 g/L in elderly women and 140 g/L in elderly men.

Goals of Therapy
Alleviate the signs and symptoms of anemia Determine and address the underlying cause(s) of the anemia Restore normal or adequate Hgb level improve quality of life 2 possibly prolong survival3 Avoid allogeneic red cell transfusion

Signs and symptoms of anemia occur when the oxygen-carrying capacity of the blood is unable to meet the oxygen requirements of body tissues (Figure 1 - Evaluation of Anemia).1 Identify the underlying cause of anemia. Underlying cause(s) may include medications (cytotoxic agents, antiretrovirals, ribavirin, folate antagonists, etc.), alcohol use, diet (vegans are at particular risk for vitamin B 12 deficiency), gastrointestinal complaints (blood loss, malabsorption, gastric or terminal ileal surgery), menorrhagia history, cancer, impaired kidney/liver/thyroid function and chronic inflammation. Seek signs and symptoms that point to the etiology of the anemia (e.g., glossitis and koilonychia in iron deficiency, paresthesia in B 12 deficiency). Diagnostic algorithms are given as guidelines in Figure 2 - Diagnostic Algorithm for Microcytic Anemia, Figure 3 Diagnostic Algorithm for Normocytic Anemia and Figure 4 - Diagnostic Algorithm for Macrocytic Anemia, based on the traditional classification of anemia according to red cell size, as reflected in the mean cell volume (MC V).4 The serum folate level is prone to short-term fluctuations and may be misleading. The red blood cell (RBC ) folate level reflects time-averaged folate availability and is a more reliable indicator of tissue folate adequacy.5 There is significant intra- and inter-individual variation in serum cobalamin levels, so patients with macrocytosis and borderline (as defined by the local laboratory) cobalamin levels need further assessment.6 C obalamin levels drop during pregnancy without other evidence of deficiency.7

Iron-deficiency Anemia
Nonpharmacologic C hoices Pharmacologic C hoices Therapeutic Tips

Nonpharmacologic Choices
Dietary iron, especially from foods rich in heme iron (i.e., liver; lean red meats; seafood such as oyster, clams, tuna, salmon, sardines and shrimp), can contribute to the treatment of iron deficiency anemia, but works more slowly than pharmacologic replacement therapy,8 and may not be sufficient in the face of more severe or persistent causes of iron deficiency. Vitamin C enhances the absorption of iron but the effect is small. C onsumption of foods that are good sources of vitamin C has a minimal impact on the therapy of iron deficiency anemia.

Pharmacologic Choices (Table 1)
Simple oral iron salts are the mainstay of iron supplementation therapy in most circumstances of iron deficiency …ocls.ca/tc.showPrintableChapter.action… 1/15


e-Therapeutics+ : Therapeutics : Blood …

Simple oral iron salts are the mainstay of iron supplementation therapy in most circumstances of iron deficiency anemia. a variety of salts are available, with differing amounts of elemental iron per tablet; however, the gut is limited in its ability to absorb iron and such differences have little effect on the outcome of replacement therapy the usual target dose is 105-200 mg/day of elemental iron, in divided doses Parenteral iron is reserved for patients with malabsorption or true