TRALI is an adverse reaction most often associated with the transfusion of plasma. TRALI has been defined as the onset of acute lung injury with hypoxemia (PaO2/FiO2< 300 or SpO2 <90% on room air) within 6 hours of transfusion in a patient with no previous risk of lung injury. Symptoms include shortness of breath, fever, chills, hypotension, and radiographic evidence of new onset bilateral pulmonary edema usually presenting within 2-6 hours after transfusion. Symptoms of TRALI are similar to other adverse reactions to plasma transfusion such as TACO and allergic reactions (which will be discussed later in the course); thus, differential diagnosis may be difficult. Mild cases of TRALI may be difficult to recognize and therefore the incidence of TRALI may be under-reported. TRALI symptoms often subside within 24-48 hours but the mortality rate is high (approximately 5-25% of cases). It is the most common cause of transfusion-associated mortality in the U.S.