Ultra-Restrictive Transfusion Thresholds in Critically Ill Adults: Are We Ready for the Next Step?

Abstract

Anemia is almost universal in critically ill patients, with 25% receiving blood transfusions as clinicians aim to prevent insufficient oxygen delivery. The current 'restrictive' hemoglobin (Hb) threshold of 7 g/dL for the nonbleeding critically ill population is supported by several landmark transfusion trials. While some trials have investigated lower transfusion thresholds, these were not conducted in this specific population. Transfusion is associated with various risks including transfusion-associated circulatory overload, transfusion-related acute lung injury, and hemolytic reactions. Moreover, transfusion products are scarce and expensive as they are produced from voluntary blood donations. Therefore, it is essential to limit blood transfusion to when absolutely necessary. Research indicates that several patient categories tolerate lower Hb levels than 7 g/dL. For instance, studies on acute hemodilution in healthy volunteers have shown that lower Hb levels do not lead to organ ischemia. Similarly, studies involving patients who refuse transfusions, often report lower Hb levels down to 5g/dL or less. These lower Hb levels appear to have limited impact on mortality or morbidity related outcomes. In patients with severe burns or hematological disorders, Hb levels below 7 g/dL are not associated with significant adverse outcomes. These findings suggest that the transfusion threshold for critically ill patients could potentially be lowered, as Hb levels under 7 g/dL do not inherently lead to increased mortality or morbidity. An individualized approach to deciding whether to transfuse or not might be best. This shift in transfusion practice could help reduce costs and minimize the risks associated with blood transfusions.

Keywords: Anemia; Intensive care unit; Mortality; Organ failure; Red blood cell; Transfusion; Ultra restrictive.