IRON DEFICIENCY ANEMIA
Iron deficiency anemia typically results when the intake of dietary iron is inadequate for hemoglobin synthesis. The body can store about one fourth to one third of its iron, and it is not until those stores are depleted that iron deficiency anemia actually begins to develop. Iron deficiency anemia is the most common type of ane-mia in all age groups, and it is the most common anemia in the world. More than 500 million people are affected, more com-monly in underdeveloped countries, where inadequate iron stores can result from inadequate intake of iron (seen with vegetarian diets) or from blood loss (eg, from intestinal hookworm). Iron deficiency is also common in the United States. In children, ado-lescents, and pregnant women, the cause is typically inadequate iron in the diet to keep up with increased growth. However, for most adults with iron deficiency anemia, the cause is blood loss. In fact, in adults, the cause of iron deficiency anemia should be considered to be bleeding until proven otherwise.
The most common cause of iron deficiency in men and post-menopausal women is bleeding (from ulcers, gastritis, inflamma-tory bowel disease, or gastrointestinal tumors). The most common cause of iron deficiency anemia in premenopausal women is men-orrhagia (excessive menstrual bleeding) and pregnancy with in-adequate iron supplementation. Patients with chronic alcoholism often have chronic blood loss from the gastrointestinal tract, which causes iron loss and eventual anemia. Other causes include iron malabsorption, as is seen after gastrectomy or with celiac disease.
Patients with iron deficiency primarily have the symptoms of ane-mia. If the deficiency is severe or prolonged, they may also have a smooth, sore tongue, brittle and ridged nails, and angular cheilosis (an ulceration of the corner of the mouth). These signs subside after iron-replacement therapy. The health history may be significant for multiple pregnancies, gastrointestinal bleeding, and pica (a craving for unusual substances, such as ice, clay, or laundry starch).
The most definitive method of establishing the diagnosis of iron deficiency anemia is bone marrow aspiration. The aspirate is stained to detect iron, which is at a low level or even absent. However, few patients with suspected iron deficiency anemia undergo bone marrow aspiration. In many patients, the diagnosis can be established with other tests, particularly in patients with a history of conditions that predispose them to this type of anemia.
There is a strong correlation between laboratory values mea-suring iron stores and levels of hemoglobin. After the iron stores are depleted (as reflected by low serum ferritin levels), the hemo-globin level falls. The diminished iron stores cause small RBCs. Therefore, as the anemia progresses, the MCV, which measures the size of the RBC, also decreases. Hematocrit and RBC levels are also low in relation to the hemoglobin level. Other laboratory tests that measure iron stores are useful but are not as consistent indicators as a low ferritin level, which reflects low iron stores. Typically, patients with iron deficiency anemia have a low serum iron level and an elevated TIBC, which measures the transport protein supplying the marrow with iron as needed (also referred to as transferrin). However, other disease states, such as infection and inflammatory conditions, can also cause a low serum iron level and TIBC with an elevated ferritin level. Therefore, the most reliable laboratory findings in evaluating iron deficiency anemia are the ferritin and hemoglobin values.
Except in the case of pregnancy, the cause of iron deficiency should be investigated. Anemia may be a sign of a curable gastro-intestinal cancer or of uterine fibroid tumors. Stool specimens should be tested for occult blood. People 50 years of age or older should have a colonoscopy, endoscopy, or other examination of the gastrointestinal tract to detect ulcerations, gastritis, polyps, or cancer. Several oral iron preparations—ferrous sulfate, ferrous gluconate, and ferrous fumarate—are available for treating iron deficiency anemia. In some cases, oral iron is poorly absorbed or poorly tolerated, or iron supplementation is needed in large amounts. In these situations, intravenous or intramuscular admin-istration of iron dextran may be needed. Before parenteral administration of a full dose, a small test dose should be adminis-tered to avoid the risk of anaphylaxis with either intravenous or in-tramuscular injections. Emergency medications (eg, epinephrine) should be close at hand.If no signs of allergic reaction have occured after 30 minutes, the remaining dose of iron may be administered. Several doses are required to replenish the patient’s iron stores.
Preventive education is important, because iron deficiency anemia is common in menstruating and pregnant women. Food sources high in iron include organ meats (beef or calf’s liver, chicken liver), other meats, beans (black, pinto, and garbanzo), leafy green veg-etables, raisins, and molasses. Taking iron-rich foods with a source of vitamin C enhances the absorption of iron.
The nurse helps the patient select a healthy diet. Nutritional counseling can be provided for those whose usual diet is inade-quate. Patients with a history of eating fad diets or strict vegetar-ian diets are counseled that such diets often contain inadequate amounts of absorbable iron. The nurse encourages patients to con-tinue iron therapy as long as it is prescribed, although they may no longer feel fatigued.
Because iron is best absorbed on an empty stomach, patients should be advised to take the supplement an hour before meals. Most patients can use the less expensive, more standard forms of ferrous sulfate. Tablets with enteric coating may be poorly
absorbed and should be avoided. Other patients have difficulty taking iron supplements because of gastrointestinal side effects (primarily constipation, but also cramping, nausea, and vomiting). Some iron formulations are designed to limit gastrointestinal side effects by the addition of a stool softener or use of sustained-release formulations to limit nausea or gastritis. Specific patient teaching aids, such as the accompanying patient education guide (Chart 33-2), can assist patients with the use of iron supplements.
If taking iron on an empty stomach causes gastric distress, the patient may need to take the iron supplement with meals. How-ever, doing so diminishes iron absorption by as much as 50%, thus prolonging the time required to replenish iron stores. Antacids or dairy products should not be taken with iron, because they greatly diminish the absorption of iron. Polysaccharide iron complex forms that have less gastrointestinal toxicity are also available, but they are more expensive.
Liquid forms of iron that cause less gastrointestinal distress are available. However, they can stain the teeth; patients should be in-structed to take this medication through a straw, to rinse the mouth with water, and to practice good oral hygiene after taking this med-ication. Finally, patients should be informed that iron salts may color the stool dark green or black. However, iron replacement therapy does not cause a false-positive result on stool analyses for occult blood.
Intramuscular supplementation is used infrequently. The vol-ume of iron required may be excessive. The intramuscular injec-tion causes some local pain and can stain the skin. These side effects are minimized by using the Z-track technique for administering iron dextran deep into the gluteus maximus muscle (buttock). Avoid vigorously rubbing the injection site after the injection. Be-cause of the problems with intramuscular administration, the in-travenous route is preferred for administration of iron dextran.