Glossary
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Transfusion Medicine
A field of medicine that is a hybrid of laboratory and clinical practices. Transfusion medicine physicians are pathologists, hematologists, anesthesiologists, and pediatricians that are experts in the science and practice of blood transfusion. They practice in blood centers, hospitals, and clinics, and may interact with patients directly or only vicariously. The term is often used interchangeably with "blood banking," but the two terms really refer to different things. The American Board of Pathology offers a certification in Blood Banking/Transfusion Medicine that requires specific training and demonstration of competence by examination.
Transfusion related Acute Lung Injury
TRALI (formerly known as "noncardiogenic pulmonary edema") is an incredibly important topic in transfusion medicine right now. It was first described by Drs. Popovsky and Moore from Mayo Clinic in the 1980s, and has recently been found to be the most common cause of transfusion-related fatality, according to data gathered from FDA reported deaths. TRALI is defined, according to a National Heart, Lung, and Blood Institute (NHLBI) consensus conference, as acute lung injury (ALI) occurring during or within six hours of transfusion. Note that the definition of ALI precludes a cardiac contribution; this is purely a pulmonary phenomenon. TRALI requires a much longer discussion than space allows here, but several important facts follow.
Most believe that TRALI can be caused by two main mechanisms, and possibly by a combination of both. TRALI was first described as occurring due to transfused donor antibodies against either recipient HLA antigens or neutrophil antigens. Such antibodies agglutinated recipient white blood cells, caused aggregation in and damage to the pulmonary capillaries, and subsequent pulmonary edema. The second mechanism (espoused originally by Dr. Silliman and colleagues in Denver and now fairly widely accepted) requires that a patient be sensitized through a significant event, such as massive transfusion or sepsis. A subsequent transfusion of stored blood, which contains metabolic byproducts known as "biologic response modifiers" (BRM) induces similar white cell agglutination and pulmonary capillary damage to that described above. As mentioned, a combination of the two mechanisms has also been postulated.
Regardless of the etiology, most cases of TRALI end in resolution of the problem over the span of several days, with aggressive respiratory support often required. However, TRALI's reported mortality rate is approximately 10%, so it is not to be taken lightly. Blood transfusion services are required by AABB to define measures to reduce the incidence of TRALI.