Acute lung injury following blood transfusion: Expanding

I n recent years blood transfusionrequirements have been increas-ing because of the increasing bur-den of chronic disease in an aging population, improvement in life-support technology with an increasing severity of illness and blood-intensive surgical pro-cedures (1, 2). In the United States alone, nearly 14 million units of blood are do-nated and 12 million units are transfused annually (2). This increased use has oc-curred despite growing concern regard-ing the safety of blood transfusions and the benefits of a restrictive transfusion strategy (3). These issues are particularly important in the critically ill. Two recent observational studies conducted in inten-sive care units ’ in Europe and the United States observed that red blood cell (RBC) transfusions were administered in ap-proximately 40 % of all patients studied (4, 5). On average, critically ill patients received almost 5 units of RBCs. This has changed little over the past decade de-spite the scrutiny of transfusion practice. Historically blood transfusion has been viewed as having obvious clinical benefit. However, transfusion practice has come under increased scrutiny. Ini-tially this was driven by concerns over transfusion related infections, human immunodeficiency virus in particular. Al-though the risk of transfusion transmit-ted infections has received considerable attention, (6) it is now becoming clear that there are other important, less rec-ognized, risks of RBC transfusion related to RBC storage effects and to immuno-modulating effects of RBC transfusions in almost all recipients (7–10). Acute respi-ratory distress immediately after the transfusion of blood and/or blood prod-ucts has been increasingly recognized over the past two decades. This syndrome known as “transfusion-related acute lung injury (TRALI), ” is considered the most common and serious complication asso-ciated with the transfusion of blood prod-ucts (11–13). However, it has recently been recognized that the transfusion of blood and blood products increases the risk of critically ill patients developing delayed respiratory failure. This article will review “classic ” TRALI and the “de-layed TRALI syndrome.