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 (often called immune TRALI); biologic response modifiers in the component can produce a similar inflammatory effect (non-immune TRALI). Published literature suggests that most cases, about 80–85%, are immune TRALI. 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, severe burns, critical illness, or massive transfusion may be especially vulnerable: the illness primes the neutrophils, and the transfusion supplies the second inflammatory stimulus. A threshold model adds that a sufficiently strong second hit can cause TRALI in a patient who was well beforehand. All plasma-containing blood components have been implicated, including red blood cells, platelets, and plasma. Red cells contain very little plasma, yet they...