Clinical question: Does a restrictive transfusion strategy improve outcomes following nonemergent cardiac surgery?
Bottom line: For patients undergoing cardiac surgery, using a restrictive transfusion strategy with a hemoglobin threshold of 7.5 g/dL does not decrease serious infections or ischemic events and may lead to increased all-cause mortality at 90 days. (LOE = 1b)
Study design: Randomized controlled trial (single-blinded)
Funding source: Government
Setting: Inpatient (any location)
This is yet another study that compares restrictive and liberal transfusion strategies, this time in a cardiac surgery population. These investigators enrolled patients undergoing nonemergency cardiac surgery (mostly coronary artery bypass grafts or valvular procedures) who had a drop of hemoglobin level to below 9 g/dL following surgery.
Patients were randomized, using concealed allocation, to the restrictive transfusion threshold group (threshold hemoglobin 7.5 g/dL) or liberal transfusion threshold group (threshold hemoglobin 9 g/dL). Patients were masked but physicians and nurses were aware of the group assignments.
In the liberal group, patients received one unit of red cell transfusion immediately after randomization followed by an additional unit if the hemoglobin level remained below or dropped below 9 g/dL again during the hospitalization. In the restrictive group, patients received one unit of red cells only if the hemoglobin level dropped below 7.5 g/dL. An additional unit was then given if hemoglobin remained below or dropped below 7.5 g/dL again during the hospitalization. The 2 groups were similar at baseline and analysis was by intention to treat. Not surprisingly, more patients in the liberal strategy group received transfusions than did those in the restrictive strategy group (95% vs 64%).
For the primary outcome—a composite of sepsis, wound infection, stroke, myocardial infarction, gut infarction, or acute kidney injury within 3 months of randomization—there was no significant difference detected between the 2 groups. However, the restrictive group had a higher mortality rate than the liberal group (4.2% vs 2.6%; P = .045). Although this was a secondary outcome, it is possible that a restrictive strategy may be harmful in this cohort, given that they may have less cardiovascular reserve than the general patient population.
Dr. Kulkarni is an assistant professor of hospital medicine at Northwestern University in Chicago.