Transfusion and lung injury.

The respiratory tree has been viewed as an infrequent site of injury arising as a complication of transfusion. In recent years, this view has changed as investigators have shown that two complications--circulatory overload and transfusion-related acute lung injury--are relatively frequent events. Circulatory overload is a result of hypertransfusion to individuals at risk, the very young or old recipient. The reaction is due to fluid infusion which overwhelms the capacity of the left ventricle, resulting in pulmonary edema. While rarely fatal, studies have shown that such incidents result in intensive care and extended hospitalization. In the setting of orthopedic surgery, 1% of elderly patients undergoing hip or knee surgery experience circulatory overload. These events are associated with autologous, as well as allogeneic red blood cells (RBC) and fresh frozen plasma. Transfusionists need to be vigilant with transfusion therapy in this population. Phlebotomy and supplemental oxygen are the key therapies. Transfusion-related acute lung injury (TRALI) is the adult respiratory distress syndrome due to transfusion. It is associated with a significant morbidity and mortality of 5-14%, making it the third most common cause of death from transfusion in developed countries. It is characterized by the onset of acute respiratory distress, bilateral pulmonary edema and hypoxemia. It occurs within 1-2 hours of transfusion of a plasma-containing blood product. All blood components have been associated with the reaction, and rarely, intravenous immune globulin. There is no recognized profile of individuals at increased risk for TRALI. There are two purported mechanisms of injury; the vast majority of cases are associated with passively transfused complement-activating antibodies. These antibodies are either HLA (Class I or II) or granulocyte-specific. These antibodies appear to act as mediators, which result in granulocyte aggregation, activation, and microvascular pulmonary injury. With appropriate respiratory intervention, 80% of patients recover within 96 hours of the original insult. There are no permanent pulmonary sequelae.