Critical care clinics
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In health, acute anemia is accompanied by changes in the distribution of blood flows at all of the central, regional, and microcirculatory levels. This redistribution in blood flows provides the capacity to maintain tissue oxygenation with hematocrit as low as 21%. ⋯ The single clinical trial found an apparent survival benefit by not exposing patients with sepsis to blood transfusions until the hemoglobin concentration was less than 70 g/L. The question remains as to whether this observation was the consequence of a protective effect anemia or an injurious effect of transfusing old stored blood.
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Anemia may be the most common illness of critically ill patients. The majority of critically ill patients are anemic at admission to the intensive care unit (ICU), and hemoglobin concentrations typically decline during the first 3 days of ICU stay. ⋯ This patient population may be at particular risk of adverse consequences of anemia given the cardiovascular, respiratory, and metabolic compromise frequently encountered during critical illness. The etiology of anemia of critical illness is multifactorial, resulting from phlebotomy, gastrointestinal bleeding, coagulation disorders, blood loss from vascular procedures, renal failure, nutritional deficiencies,bone marrow suppression, and impaired erythropoietin response.
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In reviewing the literature, the authors noted an important variation in stated and observed transfusion practice patterns among pediatric critical care practitioners, and in published guidelines on RBC transfusion. They also noted a paucity of clinical evidence with respect to RBC transfusion to critically ill children. ⋯ The TRIPICU study is testing the safety of giving more or less RBC transfusion to stable critically ill children. Other studies must be done on the epidemiology and determinants of RBC transfusion in PICUs, on prevention of transfusion, and on alternatives to RBC transfusion (eg, erythropoietin).
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Critical care clinics · Apr 2004
ReviewEfficacy of red blood cell transfusion in the critically ill.
This article has evaluated the published data regarding the efficacy of RBC transfusions in the critically ill. Taken together, these studies generally support conservative RBC transfusion strategies in critical care to reduce the risk of transfusion-related adverse effects. The TRICC trial has established the safety ofa restrictive transfusion strategy, suggesting that physicians could minimize exposure to allogeneic RBCs by lowering their transfusion threshold. ⋯ RBC transfusion is not associated with improvements in clinical outcome in the critically ill and may result in worse outcomes in some patients. 3. Specific factors that identify patients who will improve from RBC transfusion are difficult to identify. 4. Lack of efficacy of RBC transfusion likely is related to storage time, increased endothelial adherence of stored RBCs, nitric oxide binding by free hemoglobin in stored blood, donor leukocytes, host inflammatory response, and reduced red cell deformability.
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The role of transfusion in surgery and trauma continues to evolve with our greater understanding of the true indications for and effects of transfusion. The potential adverse immune consequences and end-organ effects of blood transfusion must be weighed against the need for replacement of blood volume and oxygen-carrying capacity. The techniques to conserve blood and avoid transfusion play an important role in caring for the bleeding surgical patient. The future holds great promise for the possibility of redefining the art of blood transfusion and perhaps one day replacing it entirely.