SHOULD PATIENTS ONLY RECEIVE “NEW” BLOOD WHEN UNDERGOING CARDIAC SURGERY?

Abstract

Much has been published regarding the impact of blood product transfusion on patients undergoing cardiac surgery. Less is known about the effect of age of blood products on patient outcomes. The purpose of this study was to examine the effect of age of packed red blood cells (pRBC) on in-hospital outcomes following cardiac surgery. All patients undergoing non-emergent, on-pump cardiac surgery between January 2005 and September 2013 at a single institution were considered. Patients who received between 1U and 5U of pRBC intra-operatively or at any time post-operatively were included, and those who experienced a post-operative length of stay of >30 days were excluded. “New” blood was defined as a unit of pRBC that was drawn ≤14 days prior to transfusion, while “old” blood was defined as a unit of pRBC that was drawn >14 days prior to transfusion. Patients who received only “new” blood were compared to those who received either all “old” blood or a mixture of “new” and “old” blood. These comparisons were performed on the basis of baseline characteristics, intra-operative variables and in-hospital outcomes, including mortality, re-exploration for bleeding, prolonged ventilation > 24 hours, infection, atrial fibrillation, renal failure and a composite of the aforementioned outcomes. The risk-adjusted effect of age on the likelihood of adverse in-hospital outcomes was determined using multiple logistic regression modeling techniques. A total of 2015 patients were included in the final analysis. Of these, 1052 (52%) received only “new” blood (mean # units transfused 1.9U±1.0U), while 963 (48%) received any “old” blood (mean # units transfused 2.3U±1.3U). Patients receiving only “new” blood were more likely to be female and have unstable angina. They were more likely to have undergone isolated CABG or valve surgery and to have experienced shorter bypass and cross-clamp times. They were also less likely to have left the OR on inotropes. Post-operatively, patients receiving only “new” blood experienced fewer complications (Table 1). Following adjustment for differences in baseline and intra-operative characteristics, receiving only “new” blood was associated with a significant reduction in the composite outcome of interest (OR 0.79, 95% CI 0.65-0.95, p=0.01). This study found that receiving only “new” blood was associated with a significant reduction in rates of in-hospital adverse events when compared to patients who received any “old” blood. These results suggest that patients undergoing cardiac surgery should only receive new blood that is less than 2 weeks old.