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INTRODUCTION

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Concurrent with the development of cardiac surgery in the 1950s as a means of correcting congenital heart defects came the need for large-volume blood transfusions. In the 1960s and 1970s, the introduction of valve prostheses and direct grafting of coronary arteries also made the repair of acquired heart diseases a possibility. These landmarks, along with the early liberal use of allogeneic blood transfusion therapy, led to rapid growth of our field.

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Historically, open-heart surgery has been associated with large transfusion requirements. Some reports suggest that up to 70% of this patient population requires blood transfusions, resulting in an average of 2 to 4 donor exposures per patient.1,2 It has been reported that cardiac surgery consumes about 20% of the available blood supply in the United States, with similar figures observed worldwide.3 These relatively high rates of transfusions are mostly attributable to cardiopulmonary-bypass-induced phenomena: coagulopathy, platelet dysfunction, and red cell hemolysis all occur to varying degrees as a result of the cardiopulmonary bypass (CPB) circuit.4-6 Other mechanisms for bleeding include inherited and acquired disorders (including platelet dysfunctions, coagulation factor deficiencies, and derangements leading to excessive fibrinolysis) of numerous etiologies.7 While common transfusion reactions such as urticaria and fever are easily managed and largely benign, rarer complications like transfusion-related acute lung injury (TRALI) pose serious risks to patients (eg, the mortality rate for TRALI in critically ill populations ranges from 35–58%8,9) and provide further impetus for the avoidance of blood product transfusions when at all possible.

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Although life-threatening hemorrhage is an obvious absolute indication for blood products, many transfusions are also given to improve oxygen-carrying capacity and to avoid or reverse end-organ ischemia. Despite the potential benefits of transfusing blood to maintain end-organ oxygenation, there is a surprising lack of evidence to support the liberal use of blood transfusions in cardiac surgery. In fact, there is a growing literature base demonstrating that transfusions are associated with an increased risk of both morbidity and mortality.10-12 For example, red blood cell (RBC) transfusions have been associated with longer intensive care unit lengths of stay as well as with worse short- and long-term survival.13-15 A large prospective study identified RBC transfusion as the strongest independent predictor of all-cause morbidity and mortality following isolated coronary artery bypass grafting (CABG) and that each unit of blood transfused posed an additive risk for adverse outcomes.16

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Concerns over the negative consequences of blood transfusions are not new. As cardiac surgery grew as a discipline in the 1970s, investigators concomitantly noted an increasing incidence of transfusion-transmitted hepatitis; this public health concern first alerted patients and physicians to the concept of blood conservation. The emergence of the human immunodeficiency virus (HIV) a decade later further heightened interest in this area. Considering (1) the increased awareness of blood-borne infectious diseases, (2) the ever-present shortage of available blood donors, (3) the costs of ...

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