Fight against TRALI
Authors: Okazaki H. 
Published: October 2009

Transfusion‐related acute lung injury (TRALI) is a life‐threatening adverse reaction to transfusion. It is characterized by non‐cardiogenic pulmonary edema that develops during or within 6 h after transfusion. Transfusion of blood products or massive transfusion has long been known as a rare cause of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). Because the main causes of ALI/ARDS are sepsis and/or pneumonia, little attention has been paid to transfusion as a cause of lung injury. Owing to indifference to and underrecognition of this complication, ALI after transfusion may be attributed to other causes. Moreover, physicians tend to attribute the cause of respiratory failure to more common complications of transfusion such as allergic reaction and circulatory overload. Even if an appropriate diagnosis of non‐cardiogenic pulmonary edema is made, transfusion may not be identified as its cause. Although anti‐leukocyte antibodies have been proved to be one of the main causes of TRALI, the precise mechanism of this syndrome is poorly understood. Anti‐HLA and ‐HNA antibodies in labile blood products are reported to cause TRALI, and animal models of TRALI show that these antibodies induce lung injury under certain experimental conditions. We have recently showed that anti‐CD36 antibody caused TRALI in two patients. This finding suggests that as‐yet‐unknown antibodies other than anti‐HLA or ‐HNA antibodies might cause TRALI. According to current haemovigilance reports and previous look‐back studies, the incidence of TRALI is not very high. This finding supports the concept of the two‐hit theory of ALI, where certain patients’ clinical conditions are prerequisite in addition to transfusion for developing TRALI. A recent study in the ICU of a tertiary care medical centre has revealed a high incidence of suspected TRALI cases. This study revealed that female plasma, number of pregnancies in donors, number of donor units positive for anti‐granulocyte antibodies and anti‐HLA class II antibodies and concentration of lysophophatidylcholine in donor products are associated with developing TRALI. Our recent prospective study has revealed the predominance of male Fresh frozen plasma (FFP) FFP in post‐transfusion respiratory function when comparing male only FFP and mixed FFP in surgical patients. The incidence of TRALI in the UK was successfully reduced by using preferentially male plasma. Although TRALI has a relatively better prognosis than ALI with other causes, TRALI has still been the leading cause of transfusion‐related death in the United States in recent years. The prevention of TRALI caused by plasma products has been successful, but TRALI caused by apheresis platelets is still problematic. A recent study has suggested that the prevalence of anti‐HLA antibodies in female donors increases with the number of pregnancies. Thus, screening for anti‐HLA antibodies has emerged as an effective measure to prevent TRALI caused by apheresis platelets. At present, no single measure can thoroughly eliminate TRALI; however, early diagnosis and intervention may improve the outcome for patients with TRALI. Further study is required to elucidate the mechanisms of TRALI, which may lead to the development of preventive measures and treatment.