Substantial progress has been made in our understanding of the risks and benefits of RBC transfusion through the performance of large clinical trials. More than 7000 patients have been enrolled in trials randomly allocating patients to higher transfusion thresholds (-9-10 g/dL), referred to as liberal transfusion, or lower transfusion thresholds (-7-8 g/dL), referred to as restrictive transfusion. The results of most of the trials suggest that a restrictive transfusion strategy is safe and, in some cases, superior to a liberal transfusion strategy. However, in patients with myocardial infarction, brain injury, stroke, or hematological disorders, more large trials are needed because preliminary evidence suggests that liberal transfusion might be beneficial or trials have not been performed at all.
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