Platelet transfusions are indicated for patients suffering from or at significant risk of bleeding owing to thrombocytopenia and/or platelet dysfunction. Basic guidelines for platelet transfusion are outlined in Table 1. In general, platelets should not be transfused prophylactically in the absence of microvascular bleeding, a low platelet count in

TABLE 1 ■ Suggested Transfusion Guidelines for Platelets

Recent (within 24 hours) platelet count 10,000/mm3 (for prophylaxis)

Recent (within 24 hours) platelet count 50,000/mm3 with demonstrated microvascular bleeding ("oozing") or a planned surgical/invasive procedure

Demonstrated microvascular bleeding and a precipitous fall in platelet count; patients in the operating room who have had complicated procedures or have required more than 10 U of blood and have microvascular bleeding, giving platelets assumes adequate surgical hemostasis has been achieved

Documented platelet dysfunction (e.g., prolonged bleeding time >15 minutes, abnormal platelet function tests) with petechiae, purpura, microvascular bleeding ("oozing"), or surgical/invasive procedure

Unwarranted indications:

Empirical use with massive transfusion when patient is not having clinically evident microvascular bleeding ("oozing")

Prophylaxis in thrombotic thrombocytopenic purpura/hemolytic uremic syndrome or idiopathic thrombocytopenic purpura; extrinsic platelet dysfunction (e.g., renal failure, von Willebrand's disease)

a patient undergoing a surgical procedure, or a platelet count that has recently fallen below 10,000/mm3. Previous guidelines recommended platelet transfusion for platelet counts of 20,000/mm3 for prophylaxis in stable patients without oozing or in those not undergoing surgical or invasive procedures. More recent data, however, suggest that a threshold of 10,000/mm3 causes no added bleeding while significantly reducing use of the resource (8). Patients receiving massive transfusion should not automatically receive prophylactic platelets in the absence of microvascular bleeding (9). In such patients, hypothermia effects depressed platelet function, and platelet transfusion is generally ineffective (10). Restoration of a normal temperature returns platelet function to normal and ameliorates microvascular bleeding. Ideally, platelets should be transfused after the temperature has been corrected.

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