Changes in gene expression following trauma are related to the age of transfused packed red blood cells.

BACKGROUND Transfusion of packed red blood cells (PRBCs) is associated with an increased incidence of nosocomial infections and an increased risk of death. The duration of storage before transfusion may influence these outcomes. Here, we explore the association between the age of transfused PRBCs and specific patterns of inflammatory gene expression in severely injured trauma patients. METHODS Severely injured trauma patients requiring intensive care unit treatment and receiving transfusion of PRBCs within 24 hours of the injury were recruited. Blood samples were obtained within 2 hours of the trauma, at 24 hours, and at 72 hours. Messenger RNA was extracted from whole blood, and gene expression was quantified using quantitative polymerase chain reaction. The median age of the units of PRBCs transfused to each patient was recorded. The primary outcome measure was the change in candidate gene expression over the initial 72 hours. RESULTS Sixty-four patients were studied. Fifty-three patients (83%) were male, and the median age was 40.5 years (interquartile range [IQR], 31-59). Median Injury Severity Score (ISS) was 31.5 (IQR, 23-43), and 55 patients (86%) experienced a blunt injury. Forty-one patients (64%) developed a nosocomial infection, and 15 patients (23%) died before hospital discharge. Each patient received a median of 5 U of PRBCs (IQR, 4-9.8 U) during the first 24 hours of hospital admission. The median age of the units of PRBCs transfused in each patient was 20 days (IQR, 17-22 days). Older blood was associated with greater decreases in interleukin 12 (IL-12), IL-23, and RORγt (all p's < 0.05) gene expression over the initial 24 hours, greater decreases in IL-12 gene expression over 72 hours, and a rise in transforming growth factor β gene expression over the first 72 hours. A multivariate analysis confirmed the independence of these associations. CONCLUSION Increasing the duration of storage of PRBCs before transfusion is associated with a pattern of gene expression consistent with more severe immunosuppression. LEVEL OF EVIDENCE Epidemiologic study, level III.