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[thrombocyte + -penia]
An abnormal decrease in the number of platelets.
SYN: SEE: thrombopenia

Acute infections (such as sepsis), chronic infections (such as HIV), drugs (such as alcohol, heparin, or chemotherapeutic drugs), immune disorders (such as idiopathic thrombocytopenic purpura), hypoproliferative disorders of the bone marrow (such as leukemia and aplastic anemia), and portal hypertension (such as in cirrhosis) can all cause low platelet counts. Because platelets play a vital role in blood clotting, low levels may increase the risk of bleeding. Platelet counts below 50,000/mm3 increase the risk of hemorrhage with minor trauma; spontaneous bleeding can occur when less than 20,000 are present in a milliliter of blood.

Thrombocytopenia may produce spontaneous nosebleeds, ecchymoses, petechiae on the lower extremities, bleeding from the gums, or massive gastrointestinal, internal, or intracranial bleeding.

An assessment of the platelet concentration is a normal part of the complete blood count (CBC).

Treatment is directed at removing offending drugs or managing the underlying condition, until bleeding occurs or platelet counts drop to 10,000 or less. At this level platelet transfusions may be provided to the patient, esp. if transient bone marrow suppression by chemotherapy or radiation therapy is the cause of the thrombocytopenia.

The patient is watched for internal hemorrhage (esp. intracranial bleeding) and hematuria, hematemesis, bleeding gums, abdominal distention, melena, prolonged menstruation, epistaxis, ecchymosis, petechiae, or purpura, and is handled carefully, e.g., during blood drawing, to prevent trauma and hemorrhage. Bleeding is controlled by applying pressure to bleeding sites for at least 20 min. If arterial blood collection is necessary (for blood gases), a patient care plan should be developed with the physician and the laboratory/blood collection staff to ensure that occult bleeding does not occur. The patient’s head should be elevated when lying down. Use of a soft toothbrush or sponge stick helps to prevent injury to oral tissues. Dental flossing is avoided. Normal saline (0.9%) nasal spray or use of a humidifier moistens nasal passages and helps to prevent nosebleeds. An electric razor should be used for shaving. Stools are tested for occult bleeding. Straining at stool and coughing are discouraged; stool softeners are provided as necessary. The patient is advised never to go barefoot and to wear properly fitting shoes and socks.

During periods of active bleeding, bedrest is maintained. Platelet transfusions are administered as prescribed, and the patient is observed for chills, rigors, fever, or allergic reactions. The CBC is monitored to gauge an appropriate rise in platelet count. Acetaminophen and diphenhydramine may prevent or relieve minor transfusion reactions. In patients who have low platelet counts after receiving chemotherapy, the platelet growth factor oprelvekin (Neumega) may be prescribed to reduce the need for platelet transfusions after chemotherapy. Aspirin and other nonsteroidal anti-inflammatory agents should be avoided, as well as herbs such as feverfew, gingko, ginseng, and kava because these substances may inhibit platelet function. Drugs like corticosteroids, immunoglobulin, or gamma globulin may be prescribed to decrease platelet destruction in immune-mediated thrombocytopenia. Folate stimulates bone marrow production of platelets in patients with folate deficiency. When splenectomy is performed to decrease platelet destruction, preoperative and postoperative nursing care is provided as required.

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