Hematology is the study of blood and blood-forming tissues. The lymphatic system, which drains the fluid from the spaces around each cell and channels it into the circulatory system, is discussed in Chapter 10. Several disorders that interfere with normal function of the blood are inherited. Hemophilia, sickle cell disease, and thalassemia types of anemias are examples. Accidental tearing or cutting of the vessels of the cardiovascular system and surgery cause bleeding and loss of blood. Blunt trauma to the spleen, such as might occur in an automobile accident, may cause tearing and massive internal hemorrhage. Chemicals and transfusions of the wrong blood type can cause hemolysis (destruction of red blood cells).

Cultural Considerations

Genetic Hematologic Tendencies

• African Americans have the highest incidence of sickle cell disease.

• Pernicious anemia is more prevalent among those of Scandinavian descent and among African Americans.

• People of Middle-Eastern origin may have a genetic predisposition to thalassemia.

Some blood disorders are iatrogenic; that is, they are brought on by medical treatment. For example, blood dyscrasias (imbalance in numbers of types of cells) or other pathologic conditions of the blood can be induced through at least four kinds of actions:

• Bone marrow suppression, which interferes with the production of blood cells

• Interference with normal cell function

• Destruction of the blood cells by cytotoxic drugs

• Destruction of cells by a transfusion reaction of mismatched blood

Some antineoplastic drugs, for instance, act to depress the bone marrow, which inevitably causes a reduced supply of blood cells. Other drugs, such as phenytoin (Dilantin), primidone (Mysoline), and oral contraceptives, can produce anemia by interfering with the absorption and utilization of folic acid, a substance needed to produce RBCs. Diuretics such as furosemide (Lasix) and hydrochlorothiazide (HydroDIURIL) sometimes cause leukopenia (decreased numbers of white cells), aplastic anemia (deficient cell production due to a bone marrow disorder), and abnormally low counts of platelets and granulocytes. Procainamide hydrochloride (Pronestyl) and quinidine, which are used to correct dysrhythmias of the heart, also can cause thrombocytopenia (too few platelets), agranulocytosis (decrease in granulocyte production), and aplastic anemia. Most drugs are powerful chemicals that are capable of producing undesirable side effects, even though the drugs can be of great value.

Clinical Cues

If the patient is showing signs of a blood disorder, review the medications that are being taken, and note their side effects.

Nutritional deficiencies, such as low protein or lack of vitamin C, can interfere with erythropoiesis and normally functioning blood cells. Abnormal red cells are more prone to rapid destruction, which can result in anemia. Bone marrow damage from toxic substances may also interfere with the production of blood cells. Malignant conditions such as leukemia cause growth of abnormal blood cells and interfere with the production of normal cells. Box 16-1 presents factors that alter hematologic system function.

Nutrition Considerations

Nutrients Needed for Building Red Blood Cells (Erythropoiesis)

Nutrient	Role in Erythropoiesis	Food Sources
Cobalamin (vitamin B₁₂)	RBC maturation	Red meats, especially liver
Folic acid	RBC maturation	Green leafy vegetables, liver, meat, fish, legumes, whole grains
Iron	Hemoglobin synthesis	Liver and muscle meats, eggs, dried fruits, legumes, dark green leafy vegetables, whole-grain and enriched bread and cereals, potatoes
Vitamin B₆	Hemoglobin synthesis	Meats (especially pork and liver), wheat germ, legumes, potatoes, cornmeal, bananas
Amino acids	Synthesis of nucleoprotein	Eggs, meat, milk and milk products (cheese, ice cream), poultry, fish, legumes, nuts
Vitamin C	Conversion of folic acid to its active forms; aids in iron absorption	Citrus fruits, leafy green vegetables, strawberries, cantaloupe

RBC, red blood cell.

Box 16-1

Factors that May Alter Function of the Hematologic System

Genetic Disorders

• Hemophilia

• Sickle cell disease

• Agranulocytosis

• Fanconi syndrome

Hemorrhage (Anemia)

• Surgical blood loss

• Blood loss from childbirth or spontaneous abortion

• Traumatic blood loss

Anemia

• Iron deficiency

• Folic acid deficiency

• Pernicious anemia

• Chronic slow blood loss

• Aplastic anemia

Hemolysis

• Blood transfusion reaction

• Genetic types of anemia

Bone Marrow Suppression

• Antineoplastic agents used in treatment of cancer

• Radiation treatment used for cancer

• Excessive exposure to ionizing radiation

• Exposure to toxic chemicals that damage bone marrow

• Drugs that suppress the bone marrow

Bone Marrow Proliferation or Abnormality

• Leukemia

Prevention of hematologic disorders

When considerable blood is lost through hemorrhage, the patient becomes anemic. Sometimes excessive blood loss can occur during menstruation. Prevent hemorrhage after surgery or childbirth by vigilantly assessing the amount of blood loss and by instituting measures to stop the loss if it is excessive.

Clinical Cues

The average amount of blood loss via menstruation is less than 80 mL. A better way to estimate that blood loss is to count the number of saturated pads or tampons. Each saturated pad is equal to about 50 mL of blood loss.

The nurse can help prevent anemia by promoting proper nutrition and by educating the public about the possibility of nutritional anemia. Nutritional anemia is a particular concern for individuals who subsist mostly on “fast food.”

Elder Care Points

An elderly person, especially one who lives alone, is at high risk of poor nutrition. Problems with arthritis, vision, and chronic diseases make it more difficult for the elderly to shop for food and to prepare food. As a result, an elderly person may substitute cookies, toast, or cereal for a well-balanced meal. It is important to obtain a food intake history.

Secretion of intrinsic factor from the stomach and absorption of vitamin B₁₂ is decreased in the elderly. The lack of these substances can lead to pernicious anemia from B₁₂ deficiency (see Chapter 17).

Monitoring patients for drug side effects, and alerting the physician should blood-related side effects occur, can prevent a serious blood disorder from developing. Carefully monitoring blood transfusions and promptly reporting any untoward reaction may decrease the incidence of hemolysis from a reaction.