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Increasingly aggressive medical and surgical treatment modalities spurred dramatic growth in the use of platelet transfusions in the United States in the 1980s. This growth slowed somewhat in the 1990s, based on evidence that the threshold for transfusion can be safely set at a lower level. Worldwide, many methods are used for the preparation of platelets for transfusion. In the United States, the “platelet-rich plasma” method is popular for the separation of platelets from whole-blood donations, whereas in Canada and Europe, the “buffy coat method” is more commonly used. In addition, platelets obtained from single donors and prepared by apheresis are gaining in popularity worldwide in order to limit the numbers of donors to whom recipients are exposed and to minimize the number of contaminating leukocytes in the preparations. Many institutions are making their platelet products universally leukoreduced at the time of their preparation based on evidence that such products have a reduced incidence of adverse events. After preparation, platelets are generally stored at 20 to 24°C (68–75.2°F) in containers that are permeable to oxygen. Optimally, these preparations should be agitated continuously. Storage at lower temperatures decreases in vivo survival after transfusion, and adequate access to oxygen and agitation are required to prevent deleterious declines in pH. Platelets stored in this fashion produce satisfactory clinical responses after storage for 5 to 7 days. Currently, storage is limited to 5 days because of concerns about overgrowth of bacteria that might have inadvertently contaminated the preparation.

The clinical response to platelet transfusion can be assessed by measuring the increment in platelet concentration achieved in the patient’s blood. This measurement generally correlates directly with the dose of platelets infused and inversely with the patient’s size. Using physiologic principles, one can calculate what this response should be. Although the ideal theoretical response is occasionally achieved, on average the response is approximately half the predicted value because of immunologic and nonimmunologic clinical factors that impact negatively on the response. No single correct dose of platelets exists for all patients. On average, both the initial increment and the time to next transfusion increase with increasing platelet dose. The appropriate dose varies with the clinical circumstances, the patient’s size, and the individual response to transfusion. The traditional platelet concentration that should trigger a platelet transfusion had been 20,000/μL, but studies have shown that this level can safely be reduced to 10,000/μL in patients with production disorders that are stable. Raising the transfusion trigger above this level in response to a variety of clinical circumstances that increase the likelihood of bleeding is important. Although most platelet transfusions are given to patients with suppressed platelet production, platelet transfusion occasionally is indicated when the thrombocytopenia results from massive blood loss, cardiopulmonary bypass, splenomegaly, immune-mediated thrombocytopenia, and hereditary thrombocytopenia.

The complications of platelet transfusion most frequently result from contaminating leukocytes, red cells, plasma proteins, and microorganisms. The frequency of complications resulting from contaminating leukocytes can be reduced by prestorage leukoreduction of the ...

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