When to Order Red Blood Cell Transfusion for Patients with Anemia
Background
Hospitalists commonly order red blood cell (RBC) transfusion as a therapy for patients with anemia resulting from a variety of clinical conditions. There has been lack of consensus on when to transfuse, because patients with anemia frequently have multiple co-morbidities, including coronary artery disease and congestive heart failure, which may influence their ability to tolerate a potentially ischemic state related to anemia or to accommodate volume fluctuations related to transfusion.
Furthermore, RBC transfusions are not without inherent risk. Life-threatening transfusion reactions occur in approximately seven per million transfused blood components, and transfusion-associated circulatory overload (TACO) can develop in one in 100 transfusions.1
Recently published guidelines provide recommendations for management of hemodynamically stable adults with anemia.
Guideline Update
The AABB published guidelines in the Annals of Internal Medicine in 2012 addressing RBC transfusion thresholds.1 The updated guideline makes a recommendation that clinicians utilize a restrictive transfusion strategy. Transfusion is strongly recommended for ICU patients with hemoglobin ≤7g/dL. In post-operative surgical patients and for post-operative patients with symptomatic anemia, transfusion is recommended for hemoglobin ≤8g/dL. The authors also made a weak recommendation to transfuse for hemoglobin ≤8g/dL or for symptoms in hospitalized hemodynamically stable patients with preexisting cardiovascular disease.
These recommendations draw from past literature, along with two more recent trials examining liberal or restrictive transfusion thresholds. The newer trials increased the total number of patients studied by nearly one third compared with prior reviews.2,3 The authors also incorporated recently published systematic reviews in their analysis.
Although the definition of a restrictive transfusion threshold varied across trials, including hemoglobin ≤7g/dL and ≤8g/dL, the authors used the pooled data to provide several recommendations in the new guideline. Of note, the pooled data was underpowered to detect up to a twofold increase in risk of myocardial infarction in patients in the restrictive strategy group.1
There were insufficient data for the authors to recommend for or against a restrictive transfusion strategy in patients with acute coronary syndrome, based on very low quality evidence.
Finally, the authors recommended that symptoms and hemoglobin level should both be used in determining transfusion criteria, based on low quality of evidence.
Analysis
The current AABB guidelines have two primary differences from earlier guidelines. First, the AABB authors used GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) methodology to formalize evidence-based practice in their analysis of the literature. The authors purposely used the GRADE methodology to systematically evaluate the quality of the evidence base and explicitly state the strength of the recommendation for a particular transfusion threshold.4
Second, the AABB guidelines incorporated data from the more recently published FOCUS (Functional Outcomes in Cardiovascular patients Undergoing Surgical repair of hip fracture) and TRACS (Transfusion Requirements After Cardiac Surgery) trials, resulting in a stronger recommendation supporting the use of a restrictive transfusion strategy in non-ICU and post-operative patients. The findings of the FOCUS trial are especially applicable to hospitalists, because many patients who undergo hip fracture repair are directly cared for or are co-managed by hospitalists.
The current guidelines built upon previous guidelines that advocated a restrictive strategy (hemoglobin ≤7g/dL) in hemodynamically stable, critically ill adult patients.5 In general, restrictive transfusion strategy led to nearly 40% fewer patients receiving transfusion compared with the use of a liberal transfusion strategy.1 No additional harm to patients was evidenced in the restrictive transfusion group, though the trials were not designed to answer this question; moreover, there was no statistically significant difference in mortality or functional outcome between the two groups.