AABB’s new guidelines included two primary recommendations. First, a restrictive red blood cell (RBC) transfusion threshold of 7 g/dL — rather than 10 g/dL — should be used for hospitalized, hemodynamically stable adults. Second, an 8 g/dL threshold is recommended for patients undergoing orthopedic or cardiac surgery, as well as for those with pre-existing cardiovascular disease.
“The original AABB RBC transfusion guidelines were released in 2012. Since then, several new studies have provided valuable data enabling us to update these evidence-based recommendations to address both RBC transfusion thresholds for broader patient populations and RBC storage duration,” Miriam A. Markowitz, CEO of AABB, said in a press release.
Jeffrey Carson, MD, internist at Robert Wood Johnson University Hospital, and colleagues evaluated data from 31 randomized clinical trials (n = 12,587) that compared restrictive thresholds — in which transfusion is not indicated until a person’s hemoglobin level is 7 g/dL to 8 g/dL — with liberal thresholds, or those around 9 g/dL to 10 g/dL. The number of patients in these studies represents a near doubling from the studies used to write the 2012 guidelines, Carson said in a press release.
Restrictive RBC transfusion thresholds were not associated with higher rates of adverse clinical outcomes, including 30-day mortality, myocardial infarction, cerebrovascular accident, rebleeding, pneumonia or thromboembolism.
Because there did not appear to be harm associated with withholding transfusions, the guidelines give a strong recommendation for the restrictive threshold.
Carson and colleagues also assessed optimal RBC storage duration based on data from 13 randomized controlled trials composed of 5,515 participants who were randomly assigned to receive fresher blood (< 10 days) or standard-issue blood. The storage duration ranged from a median of 4 days (mean, 12.1 days) for fresher RBCs to a median of 19 days (mean, 28 days) for standard-issue RBCs. “One of the biggest controversies regarding transfusions is whether older blood is harmful,” Aaron Tobian, MD, PhD, associate director of transfusion medicine and associate professor of pathology at Johns Hopkins Medicine, said in a release. “However, no previous guidelines have made any recommendations on the red blood cell storage duration.” Results of this analysis showed fresher blood did not reduce mortality risk compared with standard-issue blood (RR = 1.04; 95% CI, 0.95-1.14). Researchers noted trials have not assessed the effect of long-term RBC storage (near the 42-day expiration for RBC units stored with additive solution). Thus, how AABB’s recommendation applies to centers with RBCs stored for longer than 35 days is unknown. “If data suggests no harm from the use of standard-issue blood and fresher blood would only constrain a limited resource, continuing with standard practice is appropriate,” Tobian said. AABB’s new guidelines represent “an important update” to the recommendations of 2012, Mark H. Yazer, MD, associate professor of pathology at University of Pittsburgh Medical Center, and Darrell J. Triulzi, MD, director of the division of transfusion medicine in the department of pathology and medical director of the Institute for Transfusion Medicine at University of Pittsburgh Medical Center, wrote in an accompanying editorial. “This recommendation reveals science as it should evolve; the hypothesis that the receipt of standard-issue RBC units could lead to higher morbidity and mortality was suggested by an observational study of patients undergoing cardiac surgery,” Yazer and colleagues wrote. “When this concept was tested in well-designed randomized clinical trials, the original hypothesis was shown not to be valid in patients undergoing cardiac surgery, critically ill patients or premature neonatal patients. Rather than the duration of storage, the indication for RBC transfusion remains the more pertinent clinical question. These new guidelines from the AABB represent medicine at its best in that they are evidence based.” – by Chuck Gormley Disclosure: Carson and Tobian report no relevant financial disclosures. Please see the full guidelines for a list of all other researchers’ relevant financial disclosures. Triulzi reports grants from NHLBI and personal fees from Fresenius Kaboi. Yazer reports no relevant financial disclosures.