Transfusion-associated circulatory overload (TACO) is one of the major causes of death associated with transfusions. TACO is characterized by cardiogenic pulmonary edema in transfusion recipients unable to compensate with the extra blood product volume. Since 2011, an international case definition has been used to help clinicians diagnose and report cases of TACO in patients with at least 4 defined symptoms within 6 hours of transfusion. Many cases of TACO based on clinical and hemovigilance data, however, did not meet the 2011 criteria. In order to develop a revised TACO definition, the International Society of Blood Transfusion, the International Haemovigilance Network, and the AABB examined 178 transfusion reactions, including 126 TACO cases. The newly revised definition requires at least one defined criteria with onset up to 12 hours after transfusion and a total of 3 or more criteria including a pulmonary component (respiratory distress or pulmonary edema based on either chest imaging OR clinical examination). Other criteria may include cardiovascular conditions, fluid overload, and relevant biomarkers. Almost 50 transfusion experts helped to validate the new TACO definition, and all-case agreement was fairly good when clinical data was not missing. Revisions to the definition will eventually be necessary to help further distinguish TACO from transfusion-associated acute lung injury (TRALI) and other respiratory transfusion reactions.
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