Written by Clay Smith
A restrictive vs liberal transfusion strategy in patients with acute MI was non-inferior when considering 30-day MACE (major adverse coronary events).
Why does this matter?
We’ve all heard the analogy that RBCs are like boxcars on a train that carry oxygen to the tissues. Sometimes, you just need more boxcars, right?
REALITY check – boxcars ≠ better outcomes
This was a multicenter RCT with 668 patients with acute MI and hemoglobin 7-10 g/dL. Half had a more liberal hemoglobin transfusion trigger of <10; the other half had a more restrictive hemoglobin transfusion trigger of <7. For the primary outcome of 30-day MACE, there was no statistical difference: 11% restrictive vs 14% liberal; difference -3.0%, 95%CI -8.4% to 2.4%. The relative risk of MACE was 0.79; the 1-sided 97.5%CI was 0.00-1.19, which was below the pre-specified non-inferiority threshold of 1.25 (but still could indicate the potential for harm). All cause mortality was also lower in the restrictive group: 5.6% vs 7.7%. This tells us that the dogma of liberally transfusing patients with acute MI to “add more boxcars” is likely not beneficial and may be harmful. As in critical care patients, a restrictive transfusion strategy appears to be the best option for acute MI.
Effect of a Restrictive vs Liberal Blood Transfusion Strategy on Major Cardiovascular Events Among Patients With Acute Myocardial Infarction and Anemia: The REALITY Randomized Clinical Trial. JAMA. 2021 Feb 9;325(6):552-560. doi: 10.1001/jama.2021.0135.