more practical than finding multiple compatible donors. Plateletpheresis products are also easier to test for bacterial contamination, a leading cause of transfusion-associated deaths. Pooling of whole blood platelets is often done in an "open" system where the platelet containers are connected in a way that could expose the platelets to air, and pooled platelets must be transfused promptly so that any contamination does not have time to grow. Problems with apheresis include the expense of the equipment used for collection. Whole blood platelets also do not require any additional donor recruitment, as they can be made from blood donations that are also used for packed red blood cells and plasma components. Thrombocytopenia due to underproduction Recipients in this category include those undergoing chemotherapy, those with myelophthisic anemia, AIDS, or with aplastic anemia. If indicated, transfusions (one thrombapheresis concentrate) should be given until recovery of platelet function, generally approximately twice weekly. Surgical bleeding due solely to thrombocytopenia occurs when platelets < 50,000/µL while spontaneous bleeding occurs when platelets < 10,000/µL. Thrombocytopenic patients can develop "dry" bleeding, that is, petechiae and ecchymoses only. They will not suffer fatal hemorrhagic events unless they first have extensive mucosal bleeding, or "wet" bleeding. Therefore, in those with no bleeding or only "dry" bleeding, the threshold for transfusion should be between 5,000 and 10,000/µL. A more conservative threshold of 20,000/µL should be used in those with a fever or other risk factors for bleeding. Those with active bleeding or prior to surgery should have a threshold of 50,000/µL. An unconfirmed, but helpful, way to determine whether a patient is recovering from chemotherapy-induced thrombocytopenia is to measure "reticulated" platelets, or young RNA-containing platelets, which signifies that the patient is starting to make new platelets. Immune thrombocytopenia Recipients in this category include those with idiopathic thrombocytopenic purpura or drug-induced thrombocytopenia. Platelet transfusions are generally not recommended for this group of patients because the underlying cause involves antibodies that destroy platelets, therefore any newly transfused platelets will also be destroyed. Platelet transfusion may be used in emergency bleeding situations where the platelets could be used by the body before the immune system destroys them. Altered platelet functions Disorders of platelet function can be congenital or acquired. Most of these disorders are mild and may respond to therapy with desmopressin (dDAVP). Transfusion is not necessarily required. However, with some more severe disorders such as Glanzmann thrombasthenia, transfusions with large amount