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Indian Journal of Medical Science Vol. 58 No. 1, January 2004 , pp. 24-25 Practitioners section Anemia A Shah MD (Med), DNB (Med); Consultant Hematologist, BSES MG Hospital and Holy Family Hospital, Mumbai, India. Correspondence: Asha Shah, 6/32, Hari-Kripa, S. V. Road, Santacruz (W), Mumbai - 400054, India. E-mail: asshah@eth.net Accepted Date 24-01-04 Code Number: ms04004 Anemia is defined as a disorder in which patient suffers from tissue hypoxia which is a consequence of a low oxygen carrying capacity of blood. Reduction in oxygen carrying capacity is functionally best characterized by hemoglobin concentration below normal, although it can also be described as reduction in red cell count or reduction in packed cell volume or hematocrit. Blood values always do not accurately reflect alterations in the red cell mass. For example, hemoglobin may be falsely low in patients who have an expanded blood volume as in pregnancy or congestive heart failure. Thus one has to be careful in evaluating anemia in these patients. Hemoglobin in the neonate is 18 _ 22 g/dl. It steadily decreases and by the age of 3 months is 14 _ 17 g/dl. Hemoglobin of adult male is between 14 _ 16 g/dl and in women of childbearing age it is 12 _ 14 g/dl. Based on these values anemia can be defined as Hemoglobin less than 14g/dl in adult male, less than 12 g/dl in adult non pregnant woman, and less than 11g/dl.in pregnant women and children. CAUSES OF ANEMIA Red cells are formed in the bone marrow from erythroid precursors. Newly formed red cells enter the circulating blood and perform the function of carrying oxygen to the tissues. The life span of the red cells is about 120 days after which they are destroyed in the reticuloendothelial system of the body. They are replaced by new red cells formed in the marrow. This process of red cell formation and red cell destruction is very well balanced so as to maintain normal red cell number or normal hemoglobin. Thus anemia can result in one or more of the following ways: 2. Anemia due to increased red cell destruction 3. Anemia due to blood loss 1. Anemia due to decreased red cell production This could be due to one or more of the following: a) Nutritional anemia Deficient intake or absorption of nutrients such as iron, folic acid, vitamin B12 leads to decreased availability of these nutrients required to form red cells, thereby causing anemia. b) Anemia of chronic disease Depression of bone marrow due to chronic inflammatory or debilitating diseases like chronic infections, chronic liver disease, renal failure, hypothyroidism can cause anemia c) Bone marrow suppression or failure Cytotoxic drugs used to treat cancers can cause profound marrow suppression and thus decrease red cell formation also. Exposure to radiation, accidental or for treatment of cancer can suppress the marrow, thus leading to anemia. Marrow failure due to conditions like aplastic anemia can present as anemia. d) Marrow infiltration In conditions like leukemia, lymphoma, myeloma and metastasis to the marrow, anemia is due to encroachment of marrow space by tumor thus suppressing normal erythropoiesis 2. Anemia due to increased red cell destruction This could be due to: a) Congenital hemolytic anemias Hemoglobinopathies: Congenital hereditary abnormalities of hemoglobin lead to formation of defective hemoglobin. Red cells containing defective hemoglobin are destroyed earlier in the reticuloendothelial system compared to red cells with normal hemoglobin, thus leading to ineffective erythropoiesis and hence anemia. eg: Thalassemias, sickle cell anemia. Membranopathies: Congenital hereditary defect in red cell membrane which leads to early destruction of red cells by the reticuloendothelial system causing anemia. eg: hereditary spherocytosis, elliptocytosis. Enzymopathies: Deficiency of certain enzymes present in the red cells eg: glucose-6-phosphate dehydrogenase leads to hemolysis of red cells on exposure to certain drugs or infections. b) Acquired hemolytic anemia Auto immune hemolytic anemia: secondary to conditions like SLE, Leukemia or even drug induced (quinine, methyl dopa etc). Hemolysis secondary to severe valvular heart disease and prosthetic valves.
3. Anemia due to blood loss a) trauma b) operative and post operative blood loss c) blood loss from the GI tract : esophageal varices, NSAID induced gastroduodenal lesions like peptic ulcer and erosions, ankylostomiasis, haemorrhoids, malignancy etc. d) menorrhagia, ante partum hemorrhage, post partum hemorrhage in women of child bearing age. e) frequent blood donation. Blood loss anemia includes the entire clinical spectrum ranging from acute fulminant bleeding producing hypovolemic shock to chronic occult blood loss leading to iron deficiency anemia. Genito urinary tract is the most common site of blood loss in women of child bearing age while in men it is the GI tract. Management of anemia depends on the identification of the cause of anemia and its reversal. Inappropriate use of hematinics such as iron in every patient of anemia for prolonged periods can be harmful, leading to iron overload. Similarly red cell transfusions are not the answer to every patient with anemia. Risks and complications of transfusion are many and well known. Hence it is important to know the etiology of anemia and treat it accordingly. Copyright by The Indian Journal of Medical Sciences |
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