In a canine pneumonia model of exchange transfusion, altering the age but not the volume of older red blood cells markedly alters outcome

BACKGROUND Massive exchange transfusion of 42‐day‐old red blood cells (RBCs) in a canine model of Staphylococcus aureus pneumonia resulted in in vivo hemolysis with increases in cell‐free hemoglobin (CFH), transferrin‐bound iron (TBI), non–transferrin‐bound iron (NTBI), and mortality. We have previously shown that washing 42‐day‐old RBCs before transfusion significantly decreased NTBI levels and mortality, but washing 7‐day‐old RBCs increased mortality and CFH levels. We now report the results of altering volume, washing, and age of RBCs. STUDY DESIGN AND METHODS Two‐year‐old purpose‐bred infected beagles were transfused with increasing volumes (5‐10, 20‐40, or 60‐80 mL/kg) of either 42‐ or 7‐day‐old RBCs (n = 36) or 80 mL/kg of either unwashed or washed RBCs with increasing storage age (14, 21, 28, or 35 days; n = 40). RESULTS All volumes transfused (5‐80 mL/kg) of 42‐day‐old RBCs resulted in alike (i.e., not significantly different) increases in TBI during transfusion as well as in CFH, lung injury, and mortality rates after transfusion. Transfusion of 80 mL/kg RBCs stored for 14, 21, 28, and 35 days resulted in increased CFH and NTBI in between levels found at 7 and 42 days of storage. However, washing RBCs of intermediate ages (14‐35 days) does not alter NTBI and CFH levels or mortality rates. CONCLUSIONS Preclinical data suggest that any volume of 42‐day‐old blood potentially increases risks during established infection. In contrast, even massive volumes of 7‐day‐old blood result in minimal CFH and NTBI levels and risks. In contrast to the extremes of storage, washing blood stored for intermediate ages does not alter risks of transfusion or NTBI and CFH clearance.