Platelet survival time study is a nuclear laboratory test performed to measure the life span of circulating platelets to assist in the diagnosis of conditions involving vascular integrity and hemostasis. Platelets are formed in the bone marrow and have a normal life span of 9 days. Disappearance of the platelets from the circulating blood depends on their destruction by the reticuloendothelial system. If the platelet survival time is decreased, a proportional decrease in the platelet count is generally seen. Within the few days of continuing platelet destruction, platelet production can increase to two to eight times its normal rate. If the production rate does not compensate for the increased rate of destruction, thrombocytopenia will persist. Many conditions reflect a diminished platelet survival time, most commonly, diabetes, vascular disorders, cirrhosis, and idiopathic thrombocytopenic purpura (ITP).

The test involves the labeling of the client's own platelets with chromated Cr 51 or indium In 111 chloride. The labeled material is reinjected IV and blood samples are drawn over a period of days. The number of platelets and their progressive reduction in numbers are determined by testing the samples and formulating a curve over the scheduled testing days. Nonlinear curve shapes indicate a pathological condition causing destruction of the platelets. Scanning can also be performed to diagnose vascular abnormalities such as thrombosis or embolism.

• IV administration of fluid or volume expanders before the study
• Large emboli that obstruct an artery and prevent the emboli from being exposed to the radionuclide in the blood
• Heparin, which can prevent visualization of an embolus
• Therapy with drugs known to alter platelet survival, unless the test is performed to evaluate the effects of such drugs

[Show Section Outline]

Indications

• Disorders that increase or decrease levels by reduced production or increased destruction of platelets (see Chapter 2 - Hemostasis and Tests of Hemostatic Functions, Table 2-6).
• Non-immune-mediated disorders associated with reduced platelet survival:
  • Disseminated intravascular coagulation associated with shock, severe crush and burn injuries, surgical trauma, tissue infarction, overwhelming sepsis, and the obstetric complication of abruptio placentae
  • Consumptive coagulopathy associated with vascular injury such as thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, and vasculitis⁷¹
  • Prosthetic heart valves
  • Arterial grafts
  • Renal transplantation
  • Peripheral vascular disease
  • Hepatic cirrhosis
  • Post-transfusion purpura or use of extracorporeal circulation during surgery
• Immune-mediated disorders associated with reduced platelet survival:
  • ITP, as revealed by extremely short platelet survival measured in minutes to hours, chronic lymphocytic leukemia, lymphomas, systemic lupus erythematosus, and isoimmune neonatal thrombocytopenia
  • Drug sensitivity reactions from heparin, quinine, sulfonamide derivatives, gold salts, digitoxin, or thiazides
  • Diagnosis and location of DVT revealed via imaging
  • Diagnosis of pulmonary embolism revealed by visualization through imaging of the adherence of the radionuclide to the emboli, although not a very sensitive test for older thrombi in the lung because adherence is reduced with aging⁷²

Contraindications

• Pregnancy, unless the benefits of performing the study greatly outweigh the risks to the fetus

[Section Outline]

• Indications
• Contraindications

Nursing Care Before the Procedure

Client preparation is the same as for any study involving the collection of peripheral blood samples (see Appendix I) and nuclear laboratory tests:

• History should include information about the hematologic status, assessment of vital signs, and results of reticulocytes, WBC, platelet counts, and hemoglobin level.

A blood specimen is drawn from the client and centrifuged to produce platelets containing plasma. The platelets are labeled with the radioactive substance and reinjected into the client's other arm. Blood samples are drawn in 48 hours and daily thereafter for 7 to 8 days. The amount of radionuclide is measured as it disappears from the circulation; this process is related to age destruction of the platelets. A graph is plotted using the number and time of platelet destruction over a period of scheduled testing days (Fig. 20—1). Imaging for DVT and pulmonary embolism can take place immediately or can be delayed to determine the degree of uptake in the affected areas.⁷³ The scanning phase is reserved for these conditions and is not to determine platelet destruction.

Nursing Care After the Procedure

Care and assessment after the test are the same as for any study involving a venipuncture for injection or collection of a peripheral blood sample (see Appendix I).

If scanning is performed, care and assessment are the same as for any nuclear scan study (see section under "Brain Scanning").

• Immediately report platelet count of less than 20,000 per µL, considered a critical level, if this laboratory test is performed.
• Assess for bleeding and blood loss from mucous membranes, skin (petechiae, ecchymoses, epistaxis, feces, hematuria, hematemesis, or hemoptysis) with thrombocytopenia.
• Provide measures to prevent bleeding with thrombocytopenia (gentle handling, trauma protection, soft toothbrush, or electric razor).
• Monitor ordered platelet infusion for treatment of thrombocytopenia.
• Monitor ordered anticoagulant therapy if thrombosis or embolus is diagnosed.
• Resume ordered administration of corticosteroid therapy for thrombocytopenia.
• Provide a written schedule for return to the laboratory and nuclear medicine department for testing or scanning, or both.
• Provide support when diagnostic findings are revealed, and assist client to cope with chronicity of a disease and the need for repeated testing and long-term therapy.