Platelets

Platelets for transfusion are obtained through whole blood donations or by plateletpheresis of a single donor. Platelets can be stored for up to 5 days at 20° to 24°C with agitation, although platelet recovery and survival is sometimes better with shorter storage periods. Generally, random donor units are given six at a time (6-pack), or the patient is given one plateletpheresis pack. Each of these totals 250 to 350 mL and contains about 4 * 10 11 platelets. Six random donor packs or one plateletpheresis pack should raise the platelet count by 50,000 to 60,000/pL in an average-size adult. The posttransfusion platelet count should be checked 1 and 24 h after platelet infusion. Transfused platelets should survive 3 to 5 days unless there is platelet consumption or refractoriness. Patients with fever, certain infections, disseminated intravascular coagulation (DIC), excessive bleeding, splenomegaly, or antibodies against the transfused platelets may be refractory to platelet transfusion. It is preferable to use ABO-compatible platelets whenever possible to avoid the passive administration of ABO-incompatible plasma. This is particularly true in patients weighing less than 40 kg and patients who receive numerous transfusions. A small amount of RBCs contaminate the platelets, so Rh-negative women of childbearing age should receive Rh-negative platelets.

The clinical indications for the transfusion of platelets depend on the underlying etiology of the thrombocytopenia, the presence or absence of active bleeding, the presence of other disease states that may cause platelet dysfunction, and the need for surgical or invasive procedures. When the patient has thrombocytopenia due to the presence of antiplatelet antibodies, platelet transfusion is generally futile. General guidelines for platelet transfusion in adults include the following:

1. When the platelet count is above 50,000/pL, excessive bleeding due to thrombocytopenia is unlikely unless there is platelet dysfunction present.

2. The platelet count should be maintained at 50,000/pL or greater in patients undergoing major surgery or in those with ongoing significant bleeding.

3. When the platelet count is between 10,000 and 50,000/pL, there is an increased risk of bleeding with trauma or invasive procedures; bleeding that develops spontaneously or as a result of invasion should be treated with platelet transfusions; patients with concurrent disease (renal or liver) causing platelet dysfunction can bleed spontaneously with these counts.

4. When the platelet count is below 10,000/pL, there is a high risk of spontaneous hemorrhage and platelets should be transfused prophylactically, although in patients with immune thrombocytopenia, there may be little or no effect to platelet transfusion.

Special platelet preparations are indicated for some patients. Those who become refractory after multiple transfusions may need HLA-matched platelets. Immunosuppressed patients should receive irradiated platelets to prevent the alloimmunization that can occur as a result of leukocyte contamination.

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