Platelet transfusions: trigger, dose, benefits, and risks

Over the last half century, platelet transfusion has been an effective therapy for the prevention and treatment of bleeding, particularly in patients with hematologic malignancies. Recent randomized trials have demonstrated that current practices may be suboptimal in a number of ways. The rationale for parsimony in the use of this powerful therapy includes previously described severe and fatal adverse outcomes (including refractoriness, hemolysis from ABO-mismatched transfusions, acute lung injury, and bacterial sepsis), newly described serious potential risks (including thrombosis and earlier leukemic recurrence), difficulty in maintaining adequate supplies of platelets, the need to place volunteer donors on cell separators to provide the product, and cost. Recent findings demonstrate that the platelet count threshold for prophylactic transfusion can be as low as 10,000/µL, and a therapeutic rather than a prophylactic strategy of transfusion for bleeding manifestations only may be equally safe for most patients. Another recently completed study suggests that very low doses of platelet transfusions (the equivalent of half a unit of apheresis platelets or two to three units of whole blood-derived platelets) are as effective at preventing bleeding as much higher doses. One question for which there are no randomized trial data is at what threshold prophylactic platelet transfusion should be given before invasive procedures or major surgery. The typically recommended threshold of 50,000/µL is based only on expert opinion, and substantial observational data indicate that this threshold leads to many transfusions that are likely unnecessary and therefore represent risk with little or no additional benefit.