Polycythemia Vera

The Polycythemias

Polycythemia refers to an increased volume of RBCs. It is a termused when the hematocrit is elevated (to more than 55% in males, more than 50% in females). Dehydration (decreased vol-ume of plasma) can cause an elevated hematocrit, but not typi-cally to the level to be considered polycythemia. Polycythemia is classified as either primary or secondary.

POLYCYTHEMIA VERA

Polycythemia vera, or primary polycythemia, is a proliferative dis-order in which the myeloid stem cells seem to have escaped nor-mal control mechanisms. The bone marrow is hypercellular, and the RBC, WBC, and platelet counts in the peripheral blood are elevated. However, the RBC elevation is predominant; the hemat-ocrit can exceed 60%. This phase can last for an extended period (10 years or longer). The spleen resumes its embryonic function of hematopoiesis and enlarges. Over time, the bone marrow may be-come fibrotic, with a resultant inability to produce as many cells  (“burnt out” or spent phase). The disease evolves into myeloid metaplasia with myelofibrosis or AML in a significant proportion of patients; this form of AML is usually refractory to standard treat-ments (Hoffman, et al., 2000). The median survival time exceeds 15 years (Gruppo Italiano Studio Policitemia, 1995).

Clinical Manifestations

Patients typically have a ruddy complexion and splenomegaly (enlarged spleen). The symptoms result from the increased blood volume (headache, dizziness, tinnitus, fatigue, paresthesias, and blurred vision) or from increased blood viscosity (angina, claudi-cation, dyspnea, and thrombophlebitis), particularly if the patient has atherosclerotic blood vessels. Another common and bother-some problem is generalized pruritus, which may be caused by histamine release due to the increased number of basophils. Eryth-romelalgia, a burning sensation in the fingers and toes, may be reported and is only partially relieved by cooling.

Assessment and Diagnostic Findings

Diagnosis is made by finding an elevated RBC mass (a nuclear medicine procedure), a normal oxygen saturation level, and an enlarged spleen. Other factors useful in establishing the diagno-sis include elevated WBC and platelet counts. The erythropoietin level is not as low as would be expected with an elevated hemat-ocrit; it is normal or only slightly low. Causes of secondary erythro-cytosis should not be present (see later discussion).

Complications

Patients with polycythemia vera are at increased risk for throm-boses resulting in a CVA (brain attack, stroke) or heart attack (MI); thrombotic complications are the most frequent cause of death. Bleeding is also a complication, possibly due to the fact that the platelets (often very large) are somewhat dysfunctional. The bleeding can be significant and can occur in the form of nosebleeds, ulcers, and frank gastrointestinal bleeding.

Medical Management

The objective of management is to reduce the high blood cell mass. Phlebotomy is an important part of therapy and can be per-formed repeatedly to keep the hematocrit within normal range. This is achieved by removing enough blood (initially 500 mL once or twice weekly) to deplete the patient’s iron stores, thereby rendering the patient iron deficient and consequently unable to continue to manufacture RBCs excessively. Patients need to be instructed to avoid iron supplements, including those within multivitamin supplements. If the patient has an elevated uric acid concentration, allopurinol (Zyloprim) is used to prevent gouty attacks. Antihistamines are not particularly effective in control-ling itching. If the patient develops ischemic symptoms, dipyri-damole (eg, Persantine) is sometimes used. Radioactive phosphorus (³²P) or chemotherapeutic agents (eg, hydroxyurea [Hydrea]) can be used to suppress marrow function, but they may increase the risk for leukemia. Patients receiving hydroxyurea ap-pear to have a lower incidence of thrombotic complications; this may result from a more controlled platelet count. The use of as-pirin to prevent thrombotic complications is controversial. Low-dose aspirin is frequently used in patients with cardiovascular disease, but even this dose is often avoided in patients with prior bleeding, especially bleeding from the gastrointestinal tract. Aspirin is also useful in diminishing pain associated with erythromelalgia. Anagrelide (Agrylin) inhibits platelet aggregation and can also be useful in controlling the thrombocytosis associated with poly-cythemia vera. Interferon alfa-2b (Intron-A) has also been stud-ied, but it may be difficult for patients to tolerate due to the frequent side effects experienced (Tefferi et al., 2000; Lengfelder, Berger, & Hehlmann, 2000).

Nursing Management

The nurse’s role is primarily that of educator. Risk factors for thrombotic complications should be assessed, and patients should be instructed regarding the signs and symptoms of thrombosis. Pa-tients with a history of bleeding are usually advised to avoid aspirin and aspirin-containing medications, because these medications alter platelet function. Minimizing alcohol intake should also be emphasized to further diminish any risk for bleeding. For pruritus, the nurse may recommend bathing in tepid or cool water, along with applications of cocoa butter–based lotions and bath products.