Pathogen-Reduced Low-Titer Group O Whole Blood for Managing Massive Blood Loss in Prehospital and Early Hospital Settings: An In Vitro Study

<b>Background/Objectives</b>: Leukoreduced low-titer group O whole blood (LTOWB) is a promising option for early transfusion in massive hemorrhages, by providing red blood cells (RBCs), plasma, and platelets in a single unit. This study aimed to assess the effects of pathogen reduction (PR) on the LTOWB quality and its suitability for emergency transfusions, including its post-thaw RBC usability. <b>Methods</b>: Whole blood from 24 donors was processed and analyzed over seven days, including post-thaw assessments. Hematological and coagulation parameters, along with atomic force microscopy, were used to assess the RBCs' morphology, cytoskeletal integrity, and nanomechanical properties. <b>Results</b>: The PR reduced the leukocyte content while preserving platelet counts at the level of the control group. Although certain clotting factors, such as fibrinogen (<i>p</i> < 0.001) and factor VIII (<i>p</i> < 0.001), were diminished after the PR, thromboelastometry results remained within reference ranges, indicating a maintained hemostatic potential. Morphological changes in RBCs were observed, but the membrane elasticity remained stable throughout storage and after thawing, indicating preserved macromechanical properties essential for hemostasis. <b>Conclusions</b>: These findings demonstrate that LTOWB treated with partial a leukoreduction and PR maintains functional and structural integrity, supporting its potential utility as a safe and effective transfusion product for managing acute blood loss.