Red Blood Cell Concentrate Storage and Survival After Cardiac Surgery

Methods | We identified all patients who underwent coronary artery bypass graft surgery, heart valve surgery, or both between 1997 and 2012 from the SWEDEHEART register, which records information on patients who undergo heart surgery in Sweden.3 Transfusion data were obtained from the SCANDAT2 database, a nationwide register of blood transfusions.4 Linkage with national health data registers provided vital status and adverse outcomes. Blood services in Sweden are part of the public health care system and follow national guidelines, whereby the oldest available blood unit of the appropriate blood type is allocated first. Storage of RBCs was classified as previously1,2 with discrete patient groups who had exclusively received blood stored less than 14 days, 14-27 days, or 28-42 days, and a mixed storage category for patients receiving blood of mixed age. Follow-up was completed on December 31, 2013. We used multivariable Cox regression to estimate the 30day, 2-year, and 10-year risk of death in relation to storage of transfused RBCs. We also considered the number of transfused units stored 28-42 days and risk of death. Associations between RBC storage and the risk of complications within 30 days of surgery were assessed using multivariable logistic regression. Both regression models were adjusted for all the factors listed in the footnote for Table 1. Statistical analyses were performed using SAS version 9.4 (SAS Institute Inc). All statistical tests were 2-sided. P values <.05 were considered statistically significant. The study was approved by the local ethics committee, which also waived informed consent.