Age of transfused red blood cells and health outcomes in two surgical cohorts

Abstract

Rationale: Red blood cells (RBC) undergo morphologic and biochemical changes during storage which may lead to adverse health risks upon transfusion. In prior studies, the effect of RBC age on health outcomes has been conflicting. We designed the study to assess the effects of RBC units' storage duration on health outcomes specifically for hospitalized patients undergoing hip fracture surgery or coronary artery bypass grafting (CABG) surgery.

Methods: Using International Classification of Diseases (ICD) 9 codes, hip fracture surgery and CABG surgery patients, who received RBC transfusions between 2008 and 2013, were retrospectively identified from the electronic medical records system. Hip fracture surgery and CABG cohorts were sub-divided into 3 blood age groups based upon RBC unit age at the time of transfusion: young blood (RBC units stored less than or equal to 14 days), old blood (RBC units were stored for greater than or equal to 28 days), or mixed blood for the remaining patients. Outcome variables were 30-day, 90-day, and inpatient mortality as well as hospital length of stay.

Results: A total of 3,182 patients were identified: 1,121 with hip fractures and 2,061 with CABG. Transfusion of old blood was associated with higher inpatient mortality in the hip fracture surgery cohort (OR 166.8, 95% CI 1.067-26064.7, p = 0.04) and a higher 30-day mortality in the CABG cohort (OR 4.55, 95% CI 1.01-20.49, p = 0.03).

Conclusions: Transfusing RBC units stored for greater than or equal to 28 days may be associated with a higher mortality for patients undergoing hip fracture or CABG.

Keywords: Cardiac surgery; Hip surgery; Outcomes; Red blood cell transfusions; Surgery.

Figure 1.

Distribution of Length of Hospital Stay by Blood Group for Each Cohort Black dot represents mean LOS: Length of Stay P value by Wilcoxon Rank Sum test used to compare Young Blood to Old Blood.

Figure 2.

Thirty and Ninety-Day Readmission Rates for Hip Surgery and Coronary Artery Bypass Graft Surgery Cohorts Black dot represents mean P value by Wilcoxon Rank Sum test used to compare Young Blood to Old Blood.