Should We Reconsider Recommendations for Red Blood Cell Transfusion?

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Very few randomized controlled trials on the benefits of red blood cell (RBC) transfusions in humans have been published. Consequently, most clinical practice guidelines are based on expert opinion, animal studies and the limited human trials available. In the absence of definitive outcome studies, numerous theoretical arguments have been put forward either to support or to condone the classic transfusion threshold of 10 g/dL. However, the limited data available from randomized controlled trials suggest that a restrictive transfusion strategy (transfusion threshold between 7 and 8 g/dL) is associated with decreased transfusion requirements, that overall morbidity (including cardiac morbidity) and mortality, hemodynamic, pulmonary and oxygen transport variables are not different between restrictive and liberal transfusion strategies and, finally, that a restrictive transfusion strategy is not associated with increased adverse outcomes. In fact, a restrictive strategy may be associated with decreased adverse outcomes in younger and less sick critical care patients. Since transfusions are administered to correct inadequate oxygen delivery, whether global or regional, reliable monitors of tissue oxygenation will be required to study the benefits (or lack thereof) of RBC transfusions. The quest for a universal transfusion trigger, the holy grail of transfusion medicine, must be abandoned. All RBC transfusions must be tailored to the patient's needs, at the moment the need arises. In conclusion, most published recommendations are appropriate but their conclusions are limited, as they are commensurate with existing knowledge. Reliable monitors to guide transfusion therapy and well conducted trials to determine optimal transfusion strategies are required.