BACKGROUND: The mortality of trauma patients requiring massive transfusion to treat hemorrhagic shock approaches 17% at 24 hours and 26% at 30 days. The use of stored RBCs is limited to less than 42 days, so older RBCs are delivered first to rapidly bleeding trauma patients. Patients who receive a greater quantity of older RBCs may have a higher risk for mortality.
METHODS AND MATERIALS: Characterizing bloodage exposure requires accounting for the age of each RBC unit and the quantity of transfused units. To address this challenge, a novel Scalar Age of Blood Index (SBI) that represents the relative distribution of RBCs received is introduced and applied to a secondary analysis of the Pragmatic, Randomized Optimal Platelet and Plasma Ratios (PROPPR) randomized controlled trial (NCT01545232, https://clinicaltrials.gov/ct2/show/ NCT01545232). The effect of the SBI is assessed on the primary PROPPR outcome, 24-hour and 30-day mortality.
RESULTS:The distributions of blood storage ages successfully maps to a parameter (SBI) that fully defines the blood age curve for each patient. SBI was a significant predictor of 24-hour and 30-day mortality in an adjusted model that had strong predictive ability (odds ratio, 1.15 [1.01-1.29], p = 0.029, C-statistic, 0.81; odds ratio, 1.14 [1.02-1.28], p = 0.019, C-statistic, 0.88, respectively).CONCLUSION: SBI is a simple scalar metric of blood age that accounts for the relative distribution of RBCs among age categories. Transfusion of older RBCs is associated with 24-hour and 30-day mortality, after adjustment for total units and clinical covariates.T rauma is a leading cause of death and disability in younger adults. 1 Critically ill trauma patients may present with multisystem injury, severe blood loss, and traumatic hemorrhagic shock (THS) requiring emergent blood transfusions, often totaling 10 or more units of RBCs. The mortality of THS is high, approaching 17% at 24 hours and 26% at 30 days. 2 As RBCs age, they undergo biochemical and metabolic changes resulting in hemolysis. [3][4][5] In animal hemorrhage models, transfusion with older RBCs exacerbates impaired coagulation and organ perfusion, increasing susceptibility to infections, inflammation, oxidative stress, organ damage, and death. 6,7 Current practices limit RBC transfusion to units less than 42 days old. However, because of their large blood transfusion requirements, there is strong potential for ABBREVIATIONS: CDF = cumulative distribution function; ISS = Injury Severity Score; NLS = nonlinear least squares; PROPPR = Pragmatic, Randomized Optimal Platelet and Plasma Ratios trial; RCTs = randomized controlled trials; ROC = receiver operating characteristic; RTS = Revised Trauma Score; SBI = Scalar Age of Blood Index; THS = traumatic hemorrhagic shock.From the