Iron deficiency anemia

With iron deficiency anemia, an inadequate supply of iron for optimal formation of red blood cells (RBCs) results in smaller (microcytic) cells with less color on staining. Body stores of iron, including plasma iron, decrease, as does transferrin, which binds with and transports iron. Insufficient body stores of iron lead to a depleted RBC mass and, in turn, a decreased hemoglobin (Hb) level (hypochromia) and decreased oxygen-carrying capacity of the blood. A common disease worldwide, iron deficiency anemia affects 10% to 30% of adults in the United States.

Causes

Iron deficiency anemia may result from:

❑ inadequate dietary intake of iron (less than 2 mg/day) — for example, during prolonged, unsupplemented periods of breast- or bottle-feeding (not eating solid foods after age 6 months) and during periods of stress, such as rapid growth in children and adolescents

❑ iron malabsorption, as in chronic diarrhea, partial or total gastrectomy, and malabsorption syndromes such as celiac disease

❑ blood loss secondary to drug-induced GI bleeding (from anticoagulants, aspirin, or steroids) or due to heavy menses, hemorrhage from trauma, a GI ulcer, cancer, or bleeding varices

❑ pregnancy, which diverts maternal iron to the fetus for erythropoiesis

❑ intravascular hemolysis-induced hemoglobinuria or paroxysmal nocturnal hemoglobinuria

❑ mechanical erythrocyte trauma caused by a prosthetic heart valve or vena cava filters.

Iron deficiency anemia is most common in premenopausal women, infants (particularly premature and low-birth-weight infants), children, and adolescents (especially girls).

Signs and symptoms

Because of the gradual progression of iron deficiency anemia, many patients are initially asymptomatic. They tend not to seek medical treatment until anemia is severe.

At advanced stages, a decreased Hb level and the consequent decrease in the blood’s oxygen-carrying capacity cause the patient to develop exertional dyspnea, fatigue, listlessness, pallor, inability to concentrate, irritability, headache, and a susceptibility to infection. Decreased oxygen perfusion causes the heart to compensate with increased cardiac output and tachycardia.

With chronic iron deficiency anemia, nails become spoon shaped and brittle, the corners of the mouth crack, the tongue turns smooth, and the patient complains of dysphagia or may develop pica. Associated neuromuscular effects include vasomotor disturbances, numbness and tingling of the extremities, and neuralgic pain.

Diagnosis

Blood studies (serum iron, total iron-binding capacity, and ferritin levels) and stores in bone marrow may confirm iron deficiency anemia. However, the results of these tests can be misleading because of complicating factors, such as infection, pneumonia, blood transfusion, and iron supplements. Characteristic blood study results include:

❑ low Hb levels (males, less than 12 g/dl; females, less than 10 g/dl)

❑ low hematocrit (males, less than 47 ml/dl; females, less than 42 ml/dl)

❑ low serum iron levels, with high iron-binding capacity

❑ low serum ferritin levels

❑ low RBC count, with microcytic and hypochromic cells (in early stages, RBC count may be normal, except in infants and children)

❑ decreased mean corpuscular Hb level (in patients with severe anemia).

Bone marrow studies reveal depleted or absent iron stores (done by staining) and normoblastic hyperplasia.

The diagnosis must rule out other forms of anemia, such as those that result from thalassemia minor, cancer, and chronic inflammatory, liver, and kidney disease.

Treatment

The first priority of treatment is to determine the underlying cause of anemia. When this is determined, iron replacement therapy can begin. The treatment of choice is an oral preparation of iron or a combination of iron and ascorbic acid (which enhances iron absorption). In some cases, iron may have to be administered parenterally — for example, if the patient is noncompliant to the oral preparation, if she needs more iron than she can take orally, if malabsorption prevents adequate iron absorption, or if a maximum rate of Hb regeneration is desired. (See Injecting iron solutions.)

Because a total-dose I.V. infusion of supplemental iron is painless and requires fewer injections, it’s usually preferred over I.M. administration. Pregnant patients and elderly patients with severe anemia, for example, should receive a total-dose infusion of iron dextran in normal saline solution over 8 hours. To minimize the risk of an allergic reaction to iron, an I.V. test dose of 0.5 ml should be given first.

Special considerations

❑ Review guidelines for managing anemia with the patient and her family. (See Supportive management in anemia.)

❑ Monitor the patient’s compliance with the prescribed iron supplement therapy. Advise her not to stop therapy, even if she feels better, because replacement of iron stores takes time.

❑ Advise the patient that milk and antacids interfere with iron absorption, but that vitamin C can increase it. Instruct her to drink liquid supplemental iron through a straw to avoid staining her teeth.

❑ Tell the patient to report adverse reactions — such as nausea, vomiting, diarrhea, constipation, fever, and severe stomach pain — which may necessitate a dosage adjustment.

❑ If the patient receives iron I.V., monitor the infusion rate carefully, and observe her for an allergic reaction. If she shows signs of such a reaction, stop the infusion and begin supportive treatment immediately. Also, watch for dizziness and headache and for thrombophlebitis around the I.V. site.

❑ Use the Z-track injection method when administering iron I.M. to prevent skin discoloration, scarring, and irritating iron deposits in the skin.

❑ Because an iron deficiency may recur, advise the patient to get regular checkups.

Prevention

Public health professionals can play a vital role in preventing iron deficiency anemia by:

❑ teaching the basics of a nutritionally balanced diet — red meats, green vegetables, eggs, whole wheat, iron-fortified bread, cereals, and milk. (No one food contains enough iron to treat iron deficiency anemia; an average-sized person with anemia would have to eat at least 10 lb [4.5 kg] of steak daily to receive therapeutic amounts of iron.)

❑ emphasizing the need for high-risk individuals — such as premature neonates, children younger than age 2, and pregnant women — to receive prophylactic oral iron, as ordered by a physician. (Children younger than age 2 should also receive supplemental cereals and formulas high in iron.)

❑ assessing a family’s dietary habits for iron intake and noting the influence of childhood eating patterns, cultural food preferences, and family income on adequate nutrition.

❑ encouraging families with deficient iron intake to eat meat, fish, and poultry; whole and enriched grains; and foods high in ascorbic acid.

❑ carefully assessing a patient’s drug history because certain drugs, such as pancreatic enzymes and vitamin E, may interfere with iron metabolism and absorption and because aspirin, steroids, and other drugs may cause GI bleeding. (Teach patients who must take gastric irritants to take these medications with food or milk.)

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Book Source Details

• Book Title: Handbook of Diseases
• Author(s): Springhouse
• Year of Publication: 2003
• Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.

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