Publications of the Week, March 8

Restrictive versus liberal transfusion strategy in patients with anemia and acute myocardial infarction

In recent years there has been considerable attention accorded to identifying clinically meaningful transfusion thresholds for hospitalized or critically ill patients with anemia. For many years this threshold for transfusion has been a hemoglobin (Hb) level <100 g/L. Based on well-designed randomized trials, a transfusion threshold of 70 g/L (target, 70-90 g/L) is appropriate in nonbleeding critically ill patients (in an intensive care setting); a threshold of 80 g/L is appropriate in postoperative patients having noncardiac surgery, especially those with preexisting coronary artery disease; and a threshold of 75 g/L is appropriate in patients having coronary artery bypass graft surgery.

This study compared a restrictive and a liberal transfusion strategy in patients with anemia and acute myocardial infarction (MI). The primary clinical outcome was major adverse cardiovascular events (MACE) at 30 days, comprising a composite of all-cause death, stroke, recurrent MI, or emergency revascularization prompted by ischemia.

Patients with a MI and Hb level of 70 to 100 g/L were randomly allocated to a restrictive (transfuse if Hb ≤80 g/L) or a liberal (transfuse if Hb ≤100 g/L) transfusion strategy. There were 668 patients studied (median age, 77 years; 57.8% men): 342 in the restrictive transfusion group (342 units of packed red blood cells transfused) and 324 in the liberal transfusion group (758 units transfused). MACE occurred in 11.0% (95% CI, 7.5-14.6) of patients in the restrictive group and in 14.0% (95% CI, 10.0-17.9) of patients in the liberal group (difference, -3.0% [95% CI, -8.4 to 2.4]), which satisfied the prespecified criterion for noninferiority. There was no statistically significant difference in the restrictive versus liberal transfusion groups for the outcomes of all-cause mortality (5.6% vs 7.7%), recurrent MI (2.1% vs 3.1%), and emergency revascularization due to coronary ischemia (1.5% vs 1.9%), but the study was not powered to assess the effect of a restrictive transfusion strategy on these outcomes and all point estimates were in favor of a restrictive strategy.

The authors concluded that in patients with acute MI and anemia a restrictive transfusion strategy was noninferior to a liberal transfusion strategy for the outcome of MACE. The findings from this study are consistent with the trend towards limiting transfusion for anemia in other clinical settings. A restrictive transfusion approach for anemia is important as a means to conserve blood products and may provide a net clinical benefit for clinically important outcomes. However, a transfusion threshold is provided for general guidance and may not be applicable to individual patients, including patients with active bleeding, those who are ambulatory and asymptomatic, or those who are palliative.