Indications for and Adverse Effects of Red-Cell Transfusion

Abstract

A pproximately 11 million units of red cells are transfused an-nually in the United States, making red-cell transfusion one of the most common medical interventions. Red cells are typically administered as a concentrate, called packed red cells, with a preservative solution (hematocrit, 60%) that allows up to 42 days of refrigerated storage. On average, transfusion of 1 unit of red cells, which has a volume of 350 ml, results in a hemoglobin increment of 1 g per deciliter in an adult with stable blood volume. In this review, we describe the evidence underlying current transfusion guide-lines, trends in use, the infectious and noninfectious risks of transfusion, and ongo-ing research. We describe the effects of transfusion in adults who have cardiovas-cular disease or gastrointestinal bleeding, who are critically ill, or who are undergoing orthopedic surgery, as well as the effects in children. Discussions of the safety of transfusion in resource-poor countries and the efficacy of transfusion in premature infants, pregnant women, and patients with hemorrhagic shock or congenital anemias are beyond the scope of this review. Indic ations for R ed -Cell Tr a nsfusion Overall Indications Randomized clinical trials have shown that earlier results from observational studies overestimated the risks associated with blood transfusion. Most trials have randomly assigned patients to a higher hemoglobin concentration as the threshold for transfusion (referred to as liberal transfusion) or to a lower hemoglobin con-centration as the threshold (referred to as restrictive transfusion). If implemented and designed correctly, such a trial design should provide guidance about transfu-sion efficacy and safety associated with clinically meaningful differences in the mean hemoglobin concentration and the number of units of blood transfused. A total of 31 trials were included in a recent systematic review and meta-analysis evaluating the efficacy of red-cell transfusion.