Photo courtesy of UAB Hospital
AABB has released new guidelines on when to perform red blood cell (RBC) transfusions and the optimal duration of RBC storage.
The guidelines state that a restrictive transfusion threshold—waiting to transfuse until a patient’s hemoglobin level is 7-8 g/dL—is safe in most clinical settings.
And, for most patients, “fresh” RBCs—stored for less than 10 days—are no safer than standard-issue RBCs—stored for up to 42 days.
“One of the biggest controversies concerning transfusion therapy is whether older blood is harmful compared to fresher blood,” said guideline author Aaron Tobian, MD, PhD, of the Johns Hopkins University School of Medicine in Baltimore, Maryland.
“Now, we have information that can accurately inform guidelines about red blood cell storage duration. If data suggest no harm from the use of standard-issue blood and fresher blood would only constrain the use of a limited resource, continuing with standard practice of using older blood is appropriate. The newly released guidelines now clearly inform the community.”
The guidelines were published in JAMA alongside a related editorial.
The recommendations in the guidelines are based on an analysis of randomized clinical trials in which researchers evaluated hemoglobin thresholds for RBC transfusion (trials conducted from 1950 through May 2016) and RBC storage duration (trials conducted from 1948 through May 2016).
For transfusion thresholds, there were 31 trials including 12,587 subjects. The results of these trials suggested that restrictive transfusion thresholds (transfusing when the hemoglobin level is 7-8 g/dL) were not associated with higher rates of adverse clinical outcomes when compared to liberal thresholds (transfusing when the hemoglobin level is 9-10 g/dL).
For RBC storage duration, there were 13 trials including 5515 subjects. The results suggested that transfusing fresher blood did not improve clinical outcomes.
Transfusion threshold
The guideline authors said it is good practice, when making transfusion decisions, to consider the patient’s hemoglobin level, the overall clinical context, patient preference, and alternative therapies.
However, in general, a hemoglobin level of 7 g/dL should serve as the threshold for transfusing adult patients who are hemodynamically stable, even if they are in critical care. This is a strong recommendation based on moderate-quality evidence.
“While the recommended threshold of 7 g/dL is consistent with previous AABB guidelines, the strength of the new recommendation reflects the quality and quantity of the new data, much of which was generated since 2012,” said guideline author Jeffrey Carson, MD, of Robert Wood Johnson University Hospital in New Brunswick, New Jersey.
“Clinically, these results show that no harm will come from waiting to transfuse a patient until the hemoglobin level reaches a lower point. The restrictive approach is associated with reductions in blood use, blood conservation, and lower expenses.”
The guidelines also state that, for patients with pre-existing cardiovascular disease and those undergoing cardiac or orthopedic surgery, the threshold should be 8 g/dL. This is a strong recommendation based on moderate-quality evidence.
Neither of the aforementioned recommendations apply to patients with acute coronary syndrome, severe thrombocytopenia, or chronic transfusion-dependent anemia.
Dr Carson said additional trials are needed to determine whether these patients benefit from transfusion at higher hemoglobin levels.
“We are about to embark on a large, international clinical trial supported by the NIH [National Institutes of Health] that will provide the evidence needed to determine the best course of action for patients who have had a heart attack,” he said.
Dr Carson and his colleagues also noted that, although the recommendations are based on the available evidence, the hemoglobin transfusion thresholds assessed may not be optimal. And the use of hemoglobin transfusion thresholds may be an imperfect surrogate for oxygen delivery.
Storage duration
The guidelines state that most patients, including neonates, should receive standard-issue RBCs (stored for 42 days or less) rather than limiting patients to only fresh RBCs (stored for less than 10 days). This is a strong recommendation based on moderate-quality evidence.
The trials analyzed showed that patients who received standard-issue RBCs faced no higher risk of complications—including 30-day mortality, myocardial infarction, cerebrovascular accident, rebleeding, pneumonia, or thromboembolism—than those who received fresh RBCs.
However, the guideline authors said the trial results may not apply to RBCs nearing their expiration date (stored for 35 to 42 days), as only a small proportion of patients in these trials were exposed to such RBCs.
Furthermore, the trials did not include patients undergoing a massive or exchange transfusion, neonates and children with underlying renal disease at higher risk of hyperkalemia, patients undergoing intrauterine transfusions, or patients with hemoglobinopathies requiring chronic transfusion support.
So the optimal RBC storage duration for these patients is unknown.
