Chapter 17 Clinical Exemplar

CLINICAL EXEMPLARS

Multiple conditions contribute to impaired clotting—more than are described in this text. Box 17.2 lists common conditions associated with impaired clotting across the lifespan. Some of these disorders are acute, whereas others are chronic; some are preventable, others are not. Further details about these conditions can be found in medical–surgical and pediatric textbooks.

FIG. 17.4 Clotting and Interrelated Concepts.

BOX 17.2  EXEMPLARS OF IMPAIRED CLOTTING

Clotting Disorders

Local

• Arterial embolism

• Venous thromboembolism

Systemic

• Disseminated intravascular coagulation

• Polycythemia

Bleeding Disorders

• Bone marrow depression

• Disseminated intravascular coagulation

• Heparin-induced thrombocytopenia

• Hemophilia A and B

• Immune thrombocytopenia purpura

• Leukemia

• Thrombocytopenia

• Sickle cell disease

• von Willebrand disease

Featured Exemplars

Venous Thromboembolism

This is a condition associated with the formation of a blood clot or thrombus in a vein. Two primary conditions are associated with venous thromboembolism: deep venous thrombosis and pulmonary embolism. Deep venous thrombosis occurs when a blood clot forms within a large deep vein (most commonly in the lower leg, thigh, or pelvis). A pulmonary embolism occurs if the clot or a piece of the clot breaks free, travels through the circulatory system, and lodges in the pulmonary vasculature. An estimated 300,000 to 600,000 individuals each year have deep venous thrombosis, which most commonly affects older adults. Sudden death occurs in an estimated 25% of individuals who experience a pulmonary embolism.12

Arterial Embolism

An arterial embolism results when a clot forms in an artery, causing a complete or partial blockage of blood flow. Obstruction of blood flow in an artery is an emergency because of a reduction or loss of oxygenated blood reaching tissues. The severity of the outcome is dependent on the degree, length of time, and location of the obstruction. An arterial thrombosis can occur in any artery, but the three most common sites are the vessels of the heart (leading to cardiac ischemia or infarction), the brain (leading to ischemic stroke), and the vessels in the legs.

Disseminated Intravascular Coagulation (DIC)

DIC is a condition that represents both excessive clotting and bleeding. The primary disorder initiates generalized clotting forming numerous thrombi resulting in multiple organ failure. The abnormal number of thrombi consume and deplete platelets and coagulation factors, leading to hemorrhage. Thrombotic manifestations occur as a result of fibrin or platelet deposits in microvasculature and include cyanosis, paralytic ileus, and kidney damage. Bleeding manifestations include oozing blood, upper gastrointestinal bleed, and hematuria. The causes are numerous, including septicemia, severe trauma, and neoplasms. DIC may affect individuals of any age. Diagnosis is based on assessment findings and a number of different laboratory tests, including platelet count, clotting times, and measurement of degradation products with the D-dimer test.10

Hemophilia

Hemophilia represents a group of inherited bleeding disorders caused by a gene mutation leading to the absence or ineffective production of clotting protein factors. The severity of the condition is determined by the level of clotting factor. The two most common types of hemophilia are factor VIII deficiency (hemophilia A) and factor IX deficiency (hemophilia B). This genetic recessive disorder of the X chromosome affects only males, although females can be carriers of the hemophilia gene. It is estimated that approximately 20,000 males in the United States have hemophilia, accounting for approximately 1 in every 5000 male births.13

Bone Marrow Suppression

Any suppression of bone marrow activity, also called myelosuppression, can reduce the production of platelets, erythrocytes, and leukocytes. When platelets are low (thrombocytopenia), abnormal bleeding occurs. Bone marrow suppression has multiple causes, including leukemia (discussed next), chemotherapy, aplastic anemia, and heparin-induced thrombocytopenia. Because there are a variety of causes, bone marrow suppression can affect people at any age.

Leukemia

This is a group of malignant diseases affecting the blood and blood-forming tissues of the bone marrow, lymph system, and spleen. Proliferation of abnormal leukocytes prevents the normal production of platelets and erythrocytes, leading to bleeding and anemia. Leukemia is classified by the maturity of the involved cell—acute (immature cells) or chronic (mature cells)—and by the type of leukocytes involved (myelogenous or lymphocytic). Acute myelogenous leukemia has increasing incidence over the age of 60 years. Acute lymphocytic leukemia has a median age of diagnosis of 15 years. Chronic myelogenous leukemia and chronic lymphocytic leukemia increase in incidence with advancing age. Most diagnoses occur after the age of 65 years.10