Introduction: First-in, first-out institutional blood management practices are based on evidence associating increased risk of sequelae from exposure to older red blood cell (RBC) transfusions. Nonetheless, research to date within the setting of cardiac surgery has been limited by previously unmeasured confounding (i.e., use of leukoreduction, timing and volume transfused).
Hypothesis: After accounting for exposure to leukoreduction and the timing and volume of RBC units, older RBC units will not increase a patient’s odds of developing post-operative sequelae following cardiac surgery.
Methods: We reviewed 659 adult patients undergoing CABG and/or valve operations between January 1, 2008-December 31, 2015 at a tertiary center. During this time period, all RBCs given to cardiac surgery patients were leukoreduced. To address confounding by timing and volume of RBCs, we analyzed patients receiving 1 or 2 units of RBCs intraoperatively. Logistic regression was used to model the maximum storage age of RBCs against a composite endpoint (prolonged mechanical ventilation, pneumonia, renal failure, operative mortality). We further explored any differences when modeling age of RBCs as quintiles and dichotomously (≥14 vs. <14 days). We present our results using odds ratios and 95% confidence intervals.
Results: The average maximum storage age of RBCs ranged from 5 to 42 days (mean 20.8, sd: 7.0). The primary endpoint occurred among 122 (18.5%) subjects. There was neither a significant association between increasing age of RBCs and our composite endpoint (OR 1.0; 95% CI 0.98, 1.04), nor evidence of confounding in univariate analysis. These findings were qualitatively unchanged when modeling age of RBCs as quintiles (Figure; ptrend=0.50) or dichotomously (OR 1.6; 95% CI 0.88, 2.79).
Conclusion: In this single center study, we did not detect a significant adverse effect of increasing age of RBCs contrary to prior conclusions. Our findings suggest that current institutional RBC storage policies that prioritize distribution of older age RBC units may not adversely impact patient outcomes following cardiac surgery.