Background: Blood transfusion is a widely used treatment that is expensive and carries a small degree of risk. The level of anemia that patients tolerate and the indications for blood transfusion are controversial.
Methods: Review of pertinent English language literature.
Results: The risk of blood transfusion from viral transmission is very low. The risk of anemia increases as hemoglobin concentration decreases. The risk is very high when the hemoglobin concentration is below 6 g/dL. The risk of death or serious morbidity increases more rapidly in patients with cardiovascular disease than patients without cardiovascular disease. There is only one adequately powered clinical trial that demonstrates that a 7 g/dL transfusion threshold is as safe, and in some subgroups, safer than a 10 g/dL threshold.
Conclusions: A restrictive transfusion threshold (7 g/dL) is recommended in most patients. In patients with cardiovascular disease, a 9-10 g/dL may be advisable, but definitive guidelines await further clinical trials. However, as with all such treatments, the decision to transfuse should be based on individual assessment of patients' signs, symptoms, and co-morbidity.