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KEY POINTS

KEY POINTS

  • Anemia is common in the critically ill and is associated with the use of red blood cell (RBC) transfusions and worse clinical outcomes.

  • Anemia management, independent of RBC transfusion, is important. This may include the use of erythropoiesis-stimulating agents and/or iron.

  • The risks of RBC transfusions have expanded and are well documented.

  • Little data support efficacy of RBC transfusions in many clinical situations in which they are given.

  • In general for critically ill patients, a restrictive strategy (consider RBC transfusion when hemoglobin ≤7 g/dL) is recommended.

  • In patients with acute coronary syndrome, consider RBC transfusion when Hb ≤8 g/dL.

  • Patient preferences and Patient Blood Management guidelines should be considered when considering blood transfusion.

  • Anemia prevention in the ICU includes efforts to reduce phlebotomy and diagnostic laboratory testing, use of pediatric or low-volume sampling tubes, and blood loss prevention.

INTRODUCTION

Anemia is very common in critically ill patients, with 95% of intensive care unit (ICU) patients anemic by day 3.1,2 In the critically ill, anemia is associated with higher morbidity and mortality as well as longer length of stay.2 Anemia in the critically ill is frequently treated with red blood cell (RBC) transfusion resulting in critically ill patients receiving large numbers of transfusions.2,3 Historically, RBC transfusions were viewed as a safe and effective means of treating anemia and improving oxygen delivery to tissues. Beginning in the early 1980s, transfusion practice began to come under scrutiny. Initially, this was primarily driven by concerns related to the risks of RBC transfusion. However, what started as a concern for RBC transfusion risks, over the last three decades has shifted to include a more critical examination of RBC transfusion benefits.

Dating to the TRICC trial in 1999, transfusion research has been focused on comparing clinical outcomes between liberal and restrictive RBC transfusion strategies.4 The goal of these studies was to identify the “appropriate” transfusion threshold (or “trigger”). This approach has led to the view that there is in fact an acceptable, or tolerable, degree of anemia, at least as an alternative to RBC transfusion.5 However, as has been recently emphasized, anemia is not an “innocent bystander” but rather is a medical condition whose management, independent of transfusion, may lead to improved clinical outcomes.6

PATHOPHYSIOLOGY OF ANEMIA IN CRITICAL ILLNESS

Anemia and Oxygen Delivery

Anemia is best defined as a reduction in RBC mass and consequently a reduction of the delivery of oxygen to tissues. As RBC mass measurement is not practical in day-to-day clinical practice, hemoglobin concentration and/or hematocrit are the common surrogates used for RBC mass. While this works well in the steady state, it may present problems in a nonsteady states such as during resuscitation where hemoglobin concentration and hematocrit might not accurately reflect RBC mass. The definition of “normal” hemoglobin ...

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