Clinical trials evaluating red blood cell transfusion thresholds: An updated systematic review and with additional focus on patients with cardiovascular disease.
Carson JL., Stanworth SJ., Alexander JH., Roubinian N., Fergusson DA., Triulzi DJ., Goodman SG., Rao SV., Doree C., Hebert PC.
BACKGROUND: Several new trials evaluating transfusion strategies in patients with cardiovascular disease have recently been published, increasing the number of enrolled patients by over 30%. The objective was to evaluate transfusion thresholds in patients with cardiovascular disease. METHODS: We conducted an updated systematic review of randomized trials that compared patients assigned to maintain a lower (restrictive transfusion strategy) or higher (liberal transfusion strategy) hemoglobin concentration. We focused on new trial data in patients with cardiovascular disease. The primary outcome was 30-day mortality. Specific subgroups were patients undergoing cardiac surgery and with acute myocardial infarction. RESULTS: A total of 37 trials that enrolled 19,049 patients were appraised. In cardiac surgery, mortality at 30days was comparable between groups (risk ratio 0.99; 95% confidence interval 0.74-1.33). In 2 small trials (n=154) in patients with myocardial infarction, the point estimate for the mortality risk ratio was 3.88 (95% CI, 0.83-18.13) favoring the liberal strategy. Overall, from 26 trials enrolling 15,681 patients, 30-day mortality was not different between restrictive and liberal transfusion strategies (risk ratio 1.0, 95% CI, 0.86-1.16). Overall and in the cardiovascular disease subgroup, there were no significant differences observed across a range of secondary outcomes. CONCLUSIONS: New trials in patients undergoing cardiac surgery establish that a restrictive transfusion strategy of 7 to 8g/dL is safe and decreased red cell use by 24%. Further research is needed to define the optimal transfusion threshold in patients with acute myocardial infarction.