Transfusion-Related Acute Lung Injury (TRALI)

Transfusion-related acute lung injury (TRALI) is an acute, non-cardiogenic pulmonary oedema that occurs during or within 6 hours after completion of a blood component transfusion. Donor antibodies, particularly anti-HLA or anti-HNA, can activate recipient neutrophils; biologic response modifiers in the component can produce a similar inflammatory effect. Activated neutrophils sequester in the pulmonary microvasculature and release substances that injure the alveolar-capillary membrane. The barrier becomes abnormally permeable, so protein-rich fluid moves into the alveoli even though the heart has not caused a pressure-related fluid overload. A two-hit model helps explain why a patient with sepsis, trauma, surgery, critical illness, or massive transfusion may be especially vulnerable: the illness primes the neutrophils, and the transfusion supplies the second inflammatory stimulus. Plasma-containing components, including platelets and fresh frozen plasma, are commonly associated with TRALI, but the absence of a recognised risk factor does not exclude it.