Assessment of the Hematologic System
The hematologic system is composed of the blood, blood cells, lymph, and organs concerned with blood formation or blood storage. Because all systems depend on circulation and lymph flow, any problem of the hematologic system has widespread consequences for health and well-being. This chapter review the normal physiology of the hematologic system and the assessment of hematologic status.
ANATOMY AND PHYSIOLOGY REVIEW
Bone Marrow. Bone marrow is the blood-forming (hematopoietic) organ. It produces most of the cellular elements of the blood, including red blood cells (RBCs, erythrocytes), white blood cells (WBCs), and platelets. Bone marrow also is involved in some aspects of the immune response. Each day, the bone marrow in a healthy adult produces and releases approximately 2.5 billion RBCs, 2.5 billion platelets, and 1 billion white blood cells (leukocytes) per kilogram of body weight. In the fetus, blood components are formed in the liver and spleen and, by the last trimester, in the bone marrow. At birth, blood-producing marrow is present in every bone. The flat bones (sternum, skull, pelvic and shoulder girdles) contain active blood-producing marrow throughout life. As a person ages, the amount of functional bone marrow decreases in the long bones and in small, irregularly shaped bones. By age 18 blood production is limited to the ends of the long bones. During adulthood, fatty tissue replaces inactive bone marrow. In older adults, the proportion of fatty marrow increases to approximately one half of the marrow found in the sternum and ribs, and only a relatively small portion of the remaining marrow continues active blood production.
The bone marrow produces all blood cells, which initially start out as stem cells. Bone marrow contains pluripotent stem cells. Pluripotent stem cells are immature and undifferentiated cells that are capable of maturing into any one of several types of blood cells: RBCs, WBCs, or platelets, depending on the body’s needs (Figure 39-1).
The next stage in cell development is the committed stem cell (also called the precursor cell or unipotent stem cell). A committed stem cell has one specific maturational pathway and matures or differentiates into only one cell type. Committed stem cells actively divide but require the presence of a specific growth factor for further development and maturation. For example, erythropoietin is a growth factor made in the kidneys that is specific for the red blood cell line. Many different growth factors influence the maturation of white blood cells and platelets.
Blood Components
Blood is composed of plasma and cells. Plasma, part of the extracellular fluid of the body, is similar to the interstitial fluid found between tissue cells. Plasma, however, contains about three to four times more protein than does interstitial fluid. There are three major types of plasma proteins: albumin, globulins, and fibrinogen. The primary function of albumin is to increase the osmotic pressure of the blood, which prevents plasma from leaking into the tissues. Globulins perform many functions, such as transporting other substances and protecting the body against infection. Globulins are also the main component of antibodies. Fibrinogen is a protein molecule that can be activated to form fibrin. Individual molecules of fibrin assemble to form large structures important in the blood-clotting process.
The cells of the blood include RBCs, WBCs, and platelets. These blood cells differ in structure, site of maturation, and function.
RED BLOOD CELLS (ERYTHROCYTES)
Red blood cells (RBCs), or erythrocytes, make up the largest proportion of blood cells. Mature RBCs have no nucleus and have a biconcave disk shape. Together with a flexible membrane, this feature allows RBCs to change their shape without breaking as they pass through narrow, winding capillaries. The number of RBCs a person has varies according to gender, age, and general health, but the normal range is from 4.4 to 5.5 million/mm3. As shown in Figures 39-1 and 39-2, RBCs start out as pluripotent stem cells, enter the myeloid pathway, and progress in stages to the mature RBC (the erythrocyte).
Healthy, mature RBCs have a life span of approximately 120 days after being released into the blood from the bone marrow. As RBCs age, their membranes become more fragile. These old cells are trapped and destroyed by fixed macrophages in the tissues, spleen, and liver. Some parts of destroyed RBCs (e.g., iron) are recycled and used in the formation of new RBCs. RBCs are responsible for producing hemoglobin (Hgb). Each normal, mature RBC contains many thousands of hemoglobin molecules (Guyton & Hall, 2000). The heme part of each hemoglobin molecule requires a molecule of iron. Only when the heme molecule is complete with iron can it transport up to four molecules of oxygen. Therefore iron is a critical component of hemoglobin.
The globin portion of the hemoglobin molecule carries carbon dioxide. RBCs also serve as a buffer and help maintain acid-base balance. The most important feature of the hemoglobin molecule is its ability to combine loosely with oxygen. With only a small drop in oxygen concentration at the tissue level, a greater increase in the transfer of oxygen from hemoglobin to the tissues occurs. This transfer is also known as oxygen dissociation. Some pathologic conditions change the speed and amount of oxygen released to the tissues.
The total number of RBCs is carefully controlled through erythropoiesis (selective maturation of stem cells into mature erythrocytes). This process ensures that enough RBCs are present for good oxygenation without having an excess concentration, which could “thicken” the blood and slow its flow. The trigger for control of erythropoiesis is tissue oxygenation. The kidney produces the RBC growth factor erythropoietin at the same rate as RBC destruction to maintain a constant normal level of circulating RBCs. When tissue oxygenation is less thaormal (hypoxia), the kidney increases the production and release of erythropoietin. This growth factor stimulates the bone marrow to increase RBC production. When tissue oxygenation is excessive, the kidney decreases the production erythropoietin, inhibiting the production of RBCs. Synthetic erythropoietin (Procrit, Epogen, EPO) is now available and appears to have the same effect on bone marrow as naturally occurring erythropoietin.
Many substances are needed to form hemoglobin and RBCs, including iron, vitamin B12, folic acid, copper, pyridoxine, cobalt, and nickel. A lack of any of these substances can lead to anemia. Anemia is the result of any condition in which either the function or the number of erythrocytes is inadequate to meet tissue oxygen demands.
WHITE BLOOD CELLS (LEUKOCYTES)
White blood cells (WBCs), or leukocytes, are the second category of blood cells. There are many types of leukocytes, and each type performs at least one specific action critical to inflammation or immunity (Table 39-1).
Most WBCs are formed in the bone marrow and are considered part of the hematopoietic system. A detailed discussion of leukocyte anatomy and function is presented in Chapter 20, because these cells provide immunity and protect against the effects of invasion, infection, and injury.
PLATELETS
Platelets are the third type of blood cells. They are the smallest of the blood cells and are formed as fragments of a giant precursor cell in the bone marrow, the megakaryocyte. Figure 39-1 shows the overall developmental pathway of blood cells, and Figure 39-3 shows specific platelet development.
Platelets stick to injured blood vessel walls and form platelet plugs that can stop the flow of blood from the injured site. They also produce substances important to coagulation. Platelets maintain blood vessel integrity by beginning the repair of damage to small blood vessels. They perform most of their functions by aggregation (clumping). Platelet production in the bone marrow also is precisely controlled by growth factors (thrombopoietin). After platelets leave the bone marrow, they are taken up by the spleen for storage and are released slowly according to the body’s needs. Normally, 80% of platelets circulate and 20% are stored in the spleen. Each platelet has a life span of 1 to 2 weeks, after which it is gradually used up or destroyed during normal clotting activities.
Accessory Organs of Hematopoiesis The spleen and liver are important accessory organs of the hematopoietic system. They help regulate the maturation of blood cells to help maintain hematologic homeostasis.
SPLEEN
The spleen is located under the diaphragm to the left of the stomach. It contains three types of tissue—white pulp, red pulp, and marginal pulp—all of which help to balance blood cell production with blood cell destruction and assist with immunologic defensive mechanisms. White pulp is filled with lymphocytes and macrophages. As whole blood circulates and filters through the white pulp, unwanted cells (e.g., bacteria and old RBCs) are removed. Red pulp is composed of vascular enlargements (sinuses) that are storage sites for RBCs and platelets. Marginal pulp contains the ends of many arteries and other blood vessels. During blood formation, the spleen destroys old or imperfect RBCs, assists in iron metabolism by breaking down the hemoglobin released from these destroyed cells, stores platelets, and filters antigens. A client who has undergone a splenectomy experiences an impairment of some immune functions. Thus after a splenectomy, the body is not efficient at disposing of many bloodborne pathogenic microorganisms and is at a greatly increased risk for infection and sepsis (Workman, 1998).
LIVER The liver is important for normal erythropoiesis and is the primary production site for prothrombin and most of the bloodclotting factors. In addition, proper liver function and bile production are critical to the formation of vitamin K in the intestinal tract. (Vitamin K is essential in the formation of blood-clotting factors VII, IX, and X and prothrombin.) Large quantities of whole blood and blood cells can be stored in the liver. The liver also converts bilirubin (one end-product of hemoglobin breakdown) to bile and stores extra iron within a storage protein called ferritin. Small amounts of erythropoietin are produced in the liver.
Hemostasis/Blood Clotting In hemostasis, selective localized blood clotting occurs in damaged blood vessels while blood circulation to all other areas is maintained. Hemostasis is a complex process that balances the production of clotting and dissolving factors. It begins with the formation of a platelet plug and continues with a series of events that eventually cause the formation of a fibrin clot. Intrinsic and extrinsic factors are involved in fibrin clot formation and blood coagulation. Three sequential processes result in blood clotting: platelet aggregation with formation of a platelet plug, the blood-clotting cascade, and the formation of a complete fibrin clot.
PLATELET AGGREGATION The formation of a platelet plug by causing platelets to aggregate (clump) together is a key requirement for blood clotting. Platelets normally circulate as individual cell-like structures. They are not attracted to each other and do not clump together until activated or until the presence of other substances causes platelet membranes to become sticky, allowing aggregation to occur. When platelets become activated and aggregate, they form large, semisolid plugs within the lumens and walls of blood vessels and disrupt blood flow. These platelet plugs are not clots and cannot provide complete hemostasis. Some substances that cause platelets to aggregate include adenosine diphosphate (ADP), calcium, thromboxane A2, and collagen. Platelets themselves can be stimulated to secrete some of these substances, whereas other substances causing platelet aggregation are exogenous. Formation of a platelet plug starts the cascade reaction that ultimately causes blood coagulation to occur through formation of a fibrin clot.
THE BLOOD-CLOTTING CASCADE The blood-clotting cascade is triggered by the formation of a platelet plug. Platelet plug formation results from intrinsic or extrinsic factors. The beginning of this cascade is rapidly amplified or enhanced, with the final result much larger than the triggering event. Cascades work like a landslide. A few small pebbles rolling down a steep hillside can dislodge large rocks and pieces of soil, causing a final enormous movement of earth. As with landslides, cascade reactions are hard to stop once set into motion. Intrinsic Factors Intrinsic factors are problems or substances directly in the blood itself that first make platelets aggregate and then proceed to activate the blood-clotting cascade (Figure 39-4).
Intrinsic events that stimulate platelet aggregation include antigen- antibody reactions, circulating debris, prolonged venous stasis, and bacterial endotoxins. Continuation of the cascade to the point of fibrin clot formation depends on the presence of sufficient amounts of all the various clotting factors and cofactors (Table 39-2).
Extrinsic Factors Platelet plugs can begin to form as a result of changes in the blood vessels rather than changes in the blood. When platelet plugs form in response to blood vessel changes, the response is said to be caused by extrinsic factors (extrinsic to the blood). The most common extrinsic events are trauma to tissues and damage to blood vessels, which exposes the platelets to collagen and stimulates aggregation. The platelet plug is formed within seconds of the trauma. The blood-clotting cascade is started sooner by the extrinsic pathway than by the intrinsic pathway because some of the steps of the intrinsic pathway are bypassed. Whether the platelet plugs were formed because of abnormal blood (intrinsic factors) or by exposure of substances from damaged blood vessels (extrinsic factors), the end result of the cascade is the same: formation of a fibrin clot and coagulation. The many steps of the cascade between the formation of a platelet plug and the formation of a fibrin clot are dependent on the presence of specific clotting factors, calcium, and more platelets. Clotting factors (see Table 39-2) are actually inactive proteins that become activated in a sequence to activate fibrinogen into fibrin. At each step, the activated protein from the previous step allows activation of the next protein. The last two steps in the cascade are the activation of thrombin from prothrombin and the conversion (by thrombin) of fibrinogen into fibrin. Only fibrin molecules can begin the formation of a true clot.
FIBRIN CLOT FORMATION Fibrinogen is a large, inactive protein molecule made in the liver and secreted into the blood. Thrombin, an enzyme, removes the end portions of fibrinogen and converts it to the active fibrin molecule. Individual fibrin molecules link together to form fibrin threads. The fibrin threads make a lattice-like meshwork that forms the base of a blood clot (Figure 39-5).
After the fibrin mesh is formed, a stabilizing factor (clotting factor XIII) tightens up the mesh, making it more dense. Additional platelets stick to the threads of the mesh and attract other blood cells and proteins to form an actual blood clot. As this clot retracts, the serum (plasma without the clotting factors) is excreted, and clot formation is complete.
FIBRINOLYSIS Because blood coagulation occurs through a rapid cascade process, in theory it keeps forming fibrin clots whenever the cascade is set into motion until all blood throughout the entire body has coagulated. Such widespread coagulation is not compatible with life. Therefore, when the blood-clotting cascade is started, counterclotting or anticoagulant forces are also started to limit clot formation to only damaged areas; normal blood flow is maintained everywhere else. When blood clotting and anticlotting actions are appropriately balanced, coagulation occurs only where needed, and normal circulation is maintained. The fibrinolytic system dissolves the fibrin clot with special enzymes (Figure 39-6).
The key event of fibrinolysis is the conversion of plasminogen to plasmin. Plasmin, an active enzyme, digests fibrin, fibrinogen, prothrombin, and factors V, VIII, and XII, thus breaking down the fibrin clot.
Hematologic Changes Associated with Aging Aging changes the cellular and plasma components of blood, making accurate assessment of the hematologic system in older adults more difficult. Chart 39-1 lists assessment tips for this population.
Several factors cause a decreased blood volume in older people. Total body water is decreased among older adults. In addition, they tend to have a lower concentration of plasma proteins and a decreased plasma osmotic pressure (possibly related to a decreased dietary intake of proteins), which also causes some loss of blood volume into the interstitial space. Bone marrow produces fewer blood cells as it ages. Total red blood cell (RBC) and white blood cell (WBC) counts (especially lymphocyte counts) are lower among older adults. Platelet counts do not appear to change with age. Lymphocytes become less reactive to antigens and have a loss of im mune function. Antibody levels and responses are lower in older adults. The leukocyte count does not rise as high in response to infection in older people as it does in young people (Workman, Ellerhorst-Ryan, & Koertge, 1993). Hemoglobin levels also change with age. Hemoglobin levels in men and women fall after middle age. Iron-deficient diets may play a role in this phenomenon.
Anticoagulants and Thrombolytics Drug therapy is commonly used to alter clotting ability or to destroy existing clots when circulation is at risk. The two broad categories of drugs are anticoagulants and thrombolytics. Both categories of agents are used widely to treat excessive or inappropriate clot formation, but their actions, side effects, and precautions are very different.
ANTICOAGULANTS Anticoagulant drugs exert their effects by interfering with one or more steps in the blood-clotting cascade. Thus these agents prevent the formation of new clots and limit or prevent the extension of formed clots. Anticoagulants have no degradative effects on existing clots. Anticoagulants are further categorized into heparin, vitamin K antagonists, and platelet aggregation inhibitors. Table 39-3 summarizes the actions of different anticoagulants. Figure 39-4 shows where in the blood-clotting cascade these agents exert their anticlotting effects.
THROMBOLYTICS Thrombolytic agents preferentially degrade fibrin threads already present in the formed blood clot. The four most extensively used agents are tissue plasminogen activator (t-PA), streptokinase (SK), reteplase, and anistreplase. The mechanism to start fibrin degradation is the activation of the inactive tissue protein plasminogen to its active form, plasmin. Plasmin directly attacks and degrades the fibrin molecule and has fewer effects on the fibrinogen molecule. The general action of all these thrombolytic agents is the selective degradation of formed fibrin clots with minimal effect on clot formation.
In general, the administration of thrombolytic agents results in clot breakdown with less disruption of blood clotting. Thrombolytic agents are the first-line therapy for conditions caused by existing small or localized formed clots, such as myocardial infarction, limited arterial thrombosis, thrombotic strokes, and occluded shunts. For some conditions (e.g., myocardial infarction), these drugs are given only within the first 6 hours after the onset of symptoms. This time limitation is not related to drug activity, because thrombolytic agents can break down clots older than 6 hours. Rather, tissue that has been anoxic for more than 6 hours is not likely to benefit from this therapy, making the risks to the client greater than the advantages.
Thrombolytic therapy has a very limited role when clotting is extensive, such as in deep vein thrombophlebitis within the pelvis or massive pulmonary emboli. In these situations clots are very large compared to their usual size in the coronary arteries. The amount of drug and duration of therapy needed for the effective breakdown of such clots is both cost prohibitive and physiologically risky. Many of these clots are not easily accessed for direct infusion of the thrombolytic agent. In addition, these clots are large, and the danger of releasing largesized particles from the clots during breakdown and having them occlude other blood vessels is much greater than the thrombolytic therapy of smaller arterial clots.
ASSESSMENT TECHNIQUES
History
DEMOGRAPHIC DATA Chart 39-2 lists questions based on Gordon’s Functional Health Patterns to ask during the assessment of hematologic function. Age and gender are important variables to obtain when assessing the client’s hematologic status. Bone marrow and immune activity diminish with ag It is also important for the nurse to collect information on the client’s occupation, hobbies, and location of housing. This information may indicate an exposure to agents or chemicals that affect bone marrow growth and hematologic function.
PERSONAL AND FAMILY HISTORY Obtaining an accurate family history is important because many bleeding disorders are inherited. The nurse asks whether anyone in the family has had hemophilia, frequent nosebleeds, postpartum hemorrhages, excessive bleeding after tooth extractions, or continuous heavy bruising in response to relatively mild trauma. Family information about sickle cell disease or sickle cell traits also is obtained. Although sickle cell disease is seen primarily among African Americans, anyone may have the trait. Personal factors to be included in the hematologic assessment are liver function, the presence of known immunologic or hematologic disorders, and current medication use. Because liver function is important in the synthesis of clotting factors, the nurse also asks about jaundice, anemia, and gallstones.
The client is asked about use of blood “thinners” such as sodium warfarin (Coumadin, Warfilone), aspirin, and other nonsteroidal anti-inflammatory drugs (NSAIDs). A person who takes aspirin on a daily basis may have bleeding problems, and many over-the-counter medications contain aspirin or other salicylates that disrupt platelet aggregation. The nurse determines all medications that the client is using or has used in the past 3 weeks. Clients are also asked about the use of antibiotics, because prolonged antibiotic therapy can lead to coagulopathies or bone marrow depression. Table 39-4 lists drugs known to alter hematologic function. Previous radiation therapy may result in some permanent impairment of hematologic function, especially if marrow-forming bones were in the path of the radiation.
DIET HISTORY Dietary pattern can alter cell quality and affect blood clotting. The nurse asks clients to record everything eaten during the previous week. This information is helpful in determining the causes of anemias and of protein, mineral, or vitamin deficiencies. Diets high in fat and carbohydrates and low in protein, iron, and vitamins can cause many types of anemia and decrease the functions of all blood cells. Clients are asked about alcohol consumption. Chronic alcoholism is associated with nutritional deficiencies and liver impairment, both of which can decrease the ability of the blood to clot. Certain dietary habits can enhance blood clotting. Diets high in vitamin K may increase the rate of blood coagulation. The nurse assesses the amount of raw, leafy green vegetables that the client consumes and whether he or she routinely takes supplemental vitamins. The amount of calcium consumed within the diet or in supplements is also assessed.
SOCIOECONOMIC STATUS The nurse assesses the client’s ability to understand and follow instructions related to proper diet, specific procedures and tests, and therapeutic regimens. Personal resources, such as finances and social support, are determined. A person with a marginal income may have a diet low in iron and protein. The nurse also notes the client’s occupation and asks about potential exposure to chemicals.
CURRENT HEALTH PROBLEMS The nurse determines whether the client has experienced swelling of the lymph nodes or excessive bruising or bleeding and whether the bleeding was spontaneous or induced by trauma. The client is asked about the amount and duration of bleeding after routine dental work. Women are asked about the presence of menorrhagia (excessive menstrual flow). They are asked to estimate the number of pads or tampons used during the most recent menstrual cycle and whether this amount represents a change from their usual pattern of menstrual flow. The nurse asks whether clots are present in menstrual blood. Clot size is estimated using coins or fruit for comparison (“clots are dime sized” or “clots are the size of lemons”). The nurse determines whether the client experiences dyspnea on exertion, palpitations, frequent infections, fevers, recent weight loss, headaches, or paresthesias. Any or all of these symptoms may accompany hematologic disease. The single most common symptom of anemia is fatigue. Clients are asked about feeling tired, needing more rest, or losing endurance during normal activities. They are asked to compare the extent and intensity of their activities during the past month with those of the same month a year ago. The nurse asks about other symptoms associated with anemia, such as vertigo, tinnitus, anorexia, dysphagia, and a sore tongue.
Physical Assessment The nurse performs a comprehensive physical assessment, because hematologic dysfunction affects the whole body. Certain problems are specific for hematologic assessment in older clients (see Chart 39-1).
SKIN ASSESSMENT The nurse inspects the color of the skin for pallor or jaundice and of the mucous membranes and nail beds for pallor or cyanosis. Pallor of the gums, conjunctivae, and palmar creases indicates decreased hemoglobin levels. The gums are also assessed for active bleeding in response to light pressure or brushing the teeth with a soft-bristled brush, and any lesions or draining areas are noted. The nurse assesses for signs of bleeding in the form of petechiae and large bruises (ecchymoses). Petechiae are pinpoint hemorrhagic lesions in the skin. Bruises may be confluent or clustered. For hospitalized clients, the nurse determines if there is bleeding from sites such as nasogastric tubes, endotracheal tubes, central lines, peripheral intravenous sites, or Foley catheters. Skin turgor and itching are noted, because dry skin or intense itching can indicate hematologic disease.
HEAD AND NECK ASSESSMENT The nurse notes pallor or ulceration of the oral mucosa. The tongue may be completely smooth in pernicious anemia and iron deficiency anemia or smooth and red iutritional deficiencies. These manifestations may be accompanied by fissures at the corners of the mouth. The nurse also observes for jaundice of the sclera. All lymph node areas are inspected and palpated. Any lymph node enlargement is documented, including whether palpation of the enlarged node causes pain. It is important to determine whether the enlarged node moves or remains fixed with palpation.
RESPIRATORY ASSESSMENT The rate and depth of respiration are assessed while the client is at rest, as well as during and after mild physical activity (e.g., walking 20 steps in 10 seconds). The nurse notes whether the client can complete a 10-word sentence without stopping for a breath. The nurse assesses whether the client is fatigued easily, experiences shortness of breath at rest or on exertion, or requires additional pillows to sleep comfortably at night. Many anemias cause these symptoms.
CARDIOVASCULAR ASSESSMENT The nurse observes for heaves, distended neck veins, edema, or signs of phlebitis. He or she also auscultates for murmurs, gallops, irregular rhythms, and abnormal blood pressure. Systolic blood pressure tends to be lower thaormal in clients with anemia. In conditions of hypercellularity, blood pressure is greater thaormal. Severe anemias can cause right-sided ventricular hypertrophy and heart disease.
RENAL AND URINARY ASSESSMENT The kidneys are extremely vascular, and bleeding problems may manifest as overt or occult hematuria (blood in the urine). The nurse inspects a voided sample of urine for color. Hematuria may be detected by grossly, bloody red or dark, brownish gold urine. The urine is tested for proteins with a urine test dipstick because hematologic problems may increase the protein content of urine. The urine sample also is tested for occult blood (Hemoccult test).
MUSCULOSKELETAL ASSESSMENT Rib or sternal tenderness is an important sign of hematologic malignancy. The nurse examines the superficial surfaces of all bones, including the ribs and sternum, by applying intermittent firm pressure with the fingertips. The client’s range of joint motion is assessed, and any swelling or joint pain is documented.
ABDOMINAL ASSESSMENT The normal adult spleen is usually not palpable. An enlarged spleen is associated with many hematologic problems. An enlarged spleen may be detected by percussion, but palpation is more reliable. The spleen lies just beneath the abdominal wall and is identified by its movement during respiration. During palpation, the client lies in a relaxed, supine position while the nurse stands on the client’s right side and palpates the left upper quadrant. The nurse palpates gently and cautiously, because an enlarged spleen may be tender and easily ruptured. Palpating the edge of the liver in the right upper quadrant of the abdomen can detect hepatic enlargement, which is often associated with hematologic problems. A normal liver may be palpable as much as 4 to
CENTRAL NERVOUS SYSTEM ASSESSMENT A thorough examination of the cranial nerves and neurologic function is necessary in many clients with hematologic disease. Vitamin B12 deficiency impairs cerebral, olfactory, spinal cord, and peripheral nerve function, and severe chronic deficiency may lead to irreversible neurologic degeneration. Many neurologic problems may develop in clients who have hematologic malignancies as a consequence of bleeding, infection, or tumor spread. When the client has a known or suspected bleeding disorder and has experienced any head trauma, the nurse expands the physical assessment to include frequent neurologic checks and mental status examinations. Other important clinical manifestations associated with impaired hematologic function include fever, chills, and night sweats.
Psychosocial Assessment The person with hematologic abnormalities may have a chronic illness (e.g., hemophilia or cancer) or an acute exacerbation of a chronic disease (e.g., pernicious anemia). In either instance each person brings his or her own coping style to the illness. After developing a rapport with the client, the nurse can learn what coping mechanisms he or she has used successfully during past illness or crises. The nurse also asks the client and family members about social support networks, community resources, and financial health. A problem in any of these areas can interfere with compliance with therapy and, ultimately, recovery.
Diagnostic Assessment
LABORATORY TESTS In hematologic disease, the most definitive signs are often the laboratory test results. Chart 39-3 lists laboratory data associated with hematologic function.
Tests of Cell Number and Function
COMPLETE BLOOD COUNT A complete blood count (CBC) includes a number of studies: red blood cell (RBC) count, white blood cell (WBC) count, hematocrit, and hemoglobin level. The RBC count measures circulating RBCs in 1 mm3 of venous blood, and the WBC count measures all leukocytes present in 1 mm3 of venous blood. To determine the percentages of different types of leukocytes circulating in the blood, a WBC count with differential leukocyte count is performed (see Chapter 20). The hematocrit (Hct) is calculated as the percentage of RBCs in the total blood volume, and the hemoglobin level represents the total amount of hemoglobin in the peripheral blood. The CBC can measure other variables of the circulating cells, including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). MCV measures the average volume or size of a single RBC and is useful for classifying anemias. When MCV is elevated, the cell is said to be abnormally large (macrocytic), as seen in megaloblastic anemias. When MCV is decreased, the cell is abnormally small (microcytic), as seen in iron deficiency anemia. MCH is the average amount of hemoglobin in a single RBC. MCHC measures the average concentration of hemoglobin in a single RBC. When the MCHC is decreased, the cell has a hemoglobin deficiency and is hypochromic, as in iron deficiency anemia.
RETICULOCYTE COUNT Another hematologic test helpful in determining bone marrow function is the reticulocyte count. A reticulocyte is an immature RBC. An elevated reticulocyte count indicates increased RBC production by the bone marrow. Normally about 2% of circulating RBCs are reticulocytes. An elevated reticulocyte count is desirable in an anemic client or after hemorrhage, because this indicates that the bone marrow is responding appropriately to a decrease in the total RBC mass. An elevated reticulocyte count without a precipitating cause may indicate a pathologic condition, such as polycythemia vera.
HEMOGLOBIN ELECTROPHORESIS Hemoglobin electrophoresis detects abnormal forms of hemoglobin, such as hemoglobin S in sickle cell disease. Hemoglobin A is the major component of hemoglobin in the normal RBC. Decreased levels of hemoglobin A with increasing levels of other types of hemoglobin are typical of some hematologic problems, such as sickle cell disease.
LEUKOCYTE ALKALINE PHOSPHATASE Leukocyte alkaline phosphatase (LAP) is an enzyme produced by normal mature neutrophils. Elevated LAP levels occur during episodes of infection or stress. An elevated neutrophil count without an accompanying elevation in LAP level is associated with chronic myelogenous leukemia.
COOMBS’ TEST The two Coombs’ tests (direct and indirect) are used for blood typing. The direct test detects the presence of antibodies (also called antiglobulins) against RBCs that may be attached to the RBCs. Although healthy people can make these antibodies, certain diseases (e.g., systemic lupus erythematosus, mononucleosis, and lymphomas) are associated with the production of antibodies directed against the body’s own RBCs. The presence of these antibodies usually causes a hemolytic anemia. The indirect Coombs’ test detects the presence of circulating antiglobulins. The test is used to determine whether the client has serum antibodies to the type of RBCs he or she is about to receive by blood transfusion.
SERUM FERRITIN, TRANSFERRIN, AND TOTAL IRON-BINDING CAPACITY Serum ferritin, transferrin, and total iron-binding capacity (TIBC) tests measure iron levels. Abnormal levels of iron and TIBC are associated with many hematologic problems, including iron deficiency anemia. The serum ferritin test measures the quantity of iron present as free iron in the plasma. The amount of serum ferritin is proportionally related to the amount of intracellular iron and represents 1% of the total body iron stores. Therefore the serum ferritin level provides a means to assess total iron stores. People with serum ferritin levels within
CAPILLARY FRAGILITY TEST The capillary fragility test, or Rumpel-Leede test, measures vascular hemostatic function by increasing intracapillary pressure in the arm. This is done by occluding venous outflow or by applying controlled negative pressure to a skin area. A blood pressure cuff is usually inflated to a pressure halfway between the systolic and diastolic pressures. This pressure is maintained for 5 minutes, and the petechiae that appear distal to the cuff are counted. Normally, five to ten petechiae appear. The capillary fragility test can help determine whether excessive bleeding or bruising results from increased capillary fragility or impaired platelet action.
BLEEDING TIME TEST The bleeding time test evaluates vascular and platelet activity during hemostasis. A special spring-loaded lancet that ensures uniform wound depth is used to make a small incision in the forearm while a blood pressure cuff remains inflated at
PROTHROMBIN TIME Prothrombin time (PT) is a measurement of how long blood takes to clot. This test reflects how much of the clotting factors II, V, VII, and X is present and how well they are functioning. When sufficient amounts of these clotting factors are present and functioning, the PT shows blood clotting between 11 and 13 seconds, or within 85% to 100% of the time needed for a control sample of blood to clot. PT is prolonged when one or more clotting factors is deficient, or when liver disease is present. Sodium warfarin (Coumadin, Warfilone’+O therapy is also monitored using PT levels. Appropriate warfarin therapy prolongs PT by 1.5 to 2 times the client’s normal PT value. Facilities are using the PT test less often to assess blood clotting because control blood is taken from different people and may not be the same from one day to the next, even in a single laboratory. To eliminate PT errors resulting from variations in control blood or in some of the chemicals used in the test, the International Normalized Ratio (INR) is used more often to assess clotting time.
INTERNATIONAL NORMALIZED RATIO The INR measures the same process as the PT but in a slightly different way—by establishing a normal mean or standard for PT. The INR is calculated by dividing the client’s PT by the established standard PT. A normal INR ranges between 0.7 and 1.8. When using the INR to monitor warfarin therapy, it should be maintained between 2.0 and 3.0 regardless of the actual PT in seconds.
PARTIAL THROMBOPLASTIN TIME Partial thromboplastin time (PTT) assesses the intrinsic coagulation cascade and evaluates the presence of factors II, V, VIII, IX, XI, and XII. PTT is prolonged whenever any of these factors is deficient, such as in hemophilia or disseminated intravascular coagulation (DIC). Because factors II, IX, and X are vitamin K dependent and are produced in the liver, liver disease can decrease their concentration and prolong PTT. Heparin (Calciparine, Liquaemin, Hepalean^) therapy is monitored by PTT. The desired ranges for therapeutic anticoagulation are 1.5 to 2.5 times the normal values. Controversy exists regarding whether this test is accurate when the blood sample is obtained through an existing vascular access device (e.g., arterial line or normal saline lock) instead of through a separate new venipuncture. Clinical studies have shown that with an appropriate discard, samples obtained through existing vascular access devices do accurately reflect the client’s activated partial thromboplastin time (see the Evidence-Based Practice for Nursing box at right).
PLATELET AGGLUTINATION/AGGREGATION Platelet aggregation, or the ability to clump, can be tested by mixing the client’s plasma with a substance called ristocetin. The degree of aggregation is noted. Aggregation can be impaired in von Willebrand’s disease and during the use of drugs such as aspirin, anti-inflammatory agents, and psychotropic agents. 1
RADIOGRAPHIC EXAMINATIONS
Assessment of the client with a suspected hematologic abnormality can include radioisotopic imaging. Isotopes are used to evaluate the bone marrow for sites of active blood cell formation and sites of iron storage. Radioactive colloids are routinely used to determine organ size and liver and spleen function. The client is given a radioactive isotope intravenously approximately 3 hours before the procedure. The client is taken to the nuclear medicine department for the scan, where he or she must lie still for approximately 1 hour. No special client preparation or follow-up care is needed for these tests. Standard x-ray studies may be used to diagnose certain hematologic disorders. For example, multiple myeloma causes characteristic bone destruction, with a “Swiss cheese” appearance on the x-ray film.
BONE MARROW ASPIRATION AND BIOPSY
A bone marrow aspiration or biopsy is often performed to evaluate the client’s hematologic status when other tests show persistent abnormal findings. Results can provide important information about bone marrow function, including the production of red blood cells (RBCs), white blood cells (WBCs), and platelets. Bone marrow aspiration and bone marrow biopsy are similar invasive procedures. In a bone marrow aspiration, cells and fluids are suctioned from the bone marrow. In a bone marrow biopsy, solid tissue and cells are obtained by coring out an area of bone marrow with a large-bore needle. A physician’s order and a signed, informed consent are obtained from the client before a bone marrow aspiration or biopsy is performed. Bone marrow aspiration may be performed by a physician, sanctioned clinical nurse specialist, nurse practitioner, or physician assistant, depending on the agency’s policy and regional law. The procedure may be performed at the client’s bedside, in an examination room, in a laboratory, or in a clinic setting. On learning what specific tests will be performed on the marrow, the nurse checks the facility’s procedure manual and checks with the hematology laboratory to determine how to handle the specimen. Some tests require the addition of heparin or other special solutions to the specimen.
CLIENT PREPARATION. Most clients experience anxiety or fear before a bone marrow aspiration. Clients who have experienced a bone marrow aspiration may have less anxiety or more anxiety depending on their previous experience. The nurse can help reduce anxiety and allay fears by providing accurate information and continuous emotional support. Some clients like to have their hand held during the procedure; other clients may want the nurse to hug or hold their entire upper body. The nurse explains the procedure to the client and says that he or she will stay during the entire procedure. Occasionally, a friend or family member is permitted to be pres ent to hold the client’s hand and provide additional emotional support. If a local anesthetic is used, the nurse explains that the injection will feel like a stinging or burning sensation. The nurse tells the client to expect a heavy sensation of pressure and pushing while the needle is being inserted. Some clients also can hear a crunching sound or feel a scraping sensation as the needle punctures the bone. The nurse explains that a brief sensation of painful pulling will be experienced as the marrow is aspirated by mild suction in the syringe. If a biopsy is performed, the client may feel more pressure and discomfort as the needle is rotated into the bone. The client is assisted onto an examining table, and the site (most commonly the iliac crest) is exposed. If this site is not available or if more marrow is needed, the sternum can be used. If the iliac crest is being used, the client is usually placed in the prone position or occasionally in the side-lying position. Depending on the tests to be performed on the specimen, a laboratory technician may also be present to ensure appropriate handling of the specimen.
PROCEDURE. The procedure usually lasts from 5 to 15 minutes. Clients may be uncomfortable and may experience pain. The type and amount of anesthesia or sedation used depends on the physician’s preference, the client’s preference and previous experience with bone marrow aspiration and biopsy, and the setting. A local anesthetic solution may be injected into the skin around the site. The client may also receive a mild tranquilizer or a rapid-acting sedative, such as midazolam hydrochloride (Versed) or lorazepam (Ativan, Apo-Lorazepam+, Novo-Lorazem). Some clients do well with guided imagery or autohypnosis. Aspiration or biopsy procedures are invasive, and sterile precautions are observed. The skin over the site is cleaned with a disinfectant solution. For an aspiration, the needle is inserted with a twisting motion, and the marrow is aspirated by pulling back on the plunger of the syringe. When sufficient marrow has been aspirated to ensure accurate analysis, the needle is carefully and rapidly withdrawn while the tissues are supported at the site. For a biopsy, a small skin incision is made, and the biopsy needle is inserted through the skin opening. Pressure and several twisting motions are performed to ensure coring and loosening of an adequate amount of marrow tissue. External pressure is applied to the site until hemostasis is ensured. A pressure dressing or sandbags may be applied to minimize bleeding at the site.
FOLLOW-UP CARE. The site is covered with a dressing after hemostasis is achieved and is observed closely for 24 hours for signs of bleeding and infection. A mild analgesic (aspirin-free) is prescribed for discomfort, and ice packs are applied over the site to limit bruising. The nurse instructs the client to inspect the site every 2 hours for the first 24 hours and to note the presence of active bleeding or bruising. The client is advised to avoid contact sports or any activity that might result in trauma to the site for 48 hours. Information obtained from bone marrow aspiration or biopsy reflects the degree and quality of bone marrow activity. The counts made on a marrow specimen can indicate whether stem cells, blast cells, committed cells, and more mature cell forms are present in the expected quantities and proportions. In addition, bone marrow aspiration or biopsy can confirm the spread of cancer cells from other tumor sites.
