Transfusion of aged packed red blood cells results in decreased tissue oxygenation in critically injured trauma patients

Background: Blood transfusion is a common event in the treatment of injured patients. The effect of red blood cell transfusion on tissue oxygenation is unclear. The transfusion of older blood has been shown to be detrimental in retrospective studies. This study aims to study the effect of the age of the blood transfused on the tissue oxygenation using near infrared spectroscopy. Methods: Thirty-two critically injured trauma patients for whom a blood transfusion had been ordered were recruited. Each patient had a transcutaneous probe placed on the thenar eminence. The probe was placed 1 hour before the transfusion and left in place until 4 hours after transfusion. Tissue oxygen saturation (StO₂) was recorded every 2 minutes. The StO₂ area under the curve (AUC) over time periods was calculated. A control group (n = 16), not transfused, was recruited. The transfusion group was divided into two groups by blood age. One group received blood less than 21 days old, (new blood, n = 15) and the other received blood 21 days old or greater (old blood, n = 17). The data were analyzed for significance with Kendall's W and Wilcoxon's signed rank test (p < 0.05). Results: Baseline characteristics such were not significantly different between groups. The baseline AUC did not differ between groups. The old blood group demonstrated a significant decline in StO ₂ comparing its baseline period to its transfusion period (p < 0.05). There was no similar decline in the control group or the new blood group. The posttransfusion period AUC for the old blood group was also lower versus baseline (p = 0.06). There was a moderate correlation between increasing age of blood and decrease in oxygenation (r = 0.5). Conclusions: There was a decrease in peripheral tissue oxygenation in patients receiving older red blood cells. There was no oxygenation decrease in patients receiving blood less than 21 days. This indicates that factors in stored blood may influence the peripheral vasculature and oxygen delivery.