Overview of platelet transfusion.

Most platelet transfusions are given to prevent bleeding in thrombocytopenic patients undergoing chemotherapy for malignancy or hematopoietic stem cell transplant. In stable, uncomplicated patients the risk of bleeding is similar until the platelet count falls to <5,000/microL. However, many patients have clinical complications that necessitate transfusion at higher counts. Therefore, the recommended indication for prophylactic transfusion is a platelet count of 10,000/microL. The usual dose of platelets is 1 apheresis unit or a pool of four to six concentrates from individual units of whole blood. The likelihood of bleeding is the same if half or double the usual dose is given, but half-dose transfusions must be given more often and double-dose transfusions less often than the standard dose. For patients with inherited defects of platelet function or acquired defects such as due to drugs or uremia, the platelet count is usually normal and prophylactic transfusion is not recommended. Transfusion may be helpful to treat serious bleeding. Patients undergoing cardiopulmonary bypass may be slightly thrombocytopenic but usually have platelet dysfunction. Transfusion is helpful to treat nonsurgical serious bleeding. In idiopathic thrombocytopenic purpura, platelet survival is short and transfusion is useful only for severe bleeding.