Introduction Platelet refrigeration decreases the risk of bacterial contamination and may preserve function better than standard-of-care room temperature storage. Benefits could include lower transfusion-related complications, decreased costs, improved hemostasis in acutely bleeding patients, and extended shelf-life. In this study, we compared the effects of 22°C and 4°C storage on the functional and activation status of apheresis platelets (APs). Methods APs (n = 5 per group) were stored for 5 days at 22°C with agitation (RT) versus at 4°C with agitation (4C+AG) and without (4C). Measurements included platelet counts, mean platelet volume, blood gas analytes, aggregation response, thromboelastography, TxB2 and sCD40L release, activation markers and microparticle formation. Results Sample pH levels were within acceptable limits for storage products (pH 6.2-7.4). Platelet glucose metabolism (P < 0.05), aggregation response (ADP: RT 0; 4C+AG 5.0 ± 0.8; 4C 5.6 ± 0.9; P < 0.05), and clot strength (MA: RT 58 ± 2; 4C+AG 63 ± 2; 4C 67 ± 2; P < 0.05) were better preserved at 4°C compared to RT storage. Refrigerated samples were more activated compared to RT (P < 0.05), although TxB2 (P < 0.05) and sCD40L release (P < 0.05) were higher at RT. Agitation did not improve the quality of 4°C-stored samples. Conclusion AP stored at 4°C maintain more viable metabolic characteristics, are hemostatically more effective, and release fewer pro-inflammatory mediators than AP stored at RT over 5 days. Given the superior bacteriologic safety of refrigerated products, these data suggest that cold-stored platelets may improve outcomes for acutely bleeding patients.

BACKGROUND Whole blood (WB) has been used in combat since World War I as it is readily available and replaces every element of shed blood. Component therapy has become standard; however, recent military successes with WB resuscitation have revived the debate regarding wider WB use. Characterization of optimal WB storage is needed. We hypothesized that refrigeration preserves WB function and that a pathogen reduction technology (PRT) based on riboflavin and ultraviolet light has no deleterious effect over 21 days of storage. STUDY DESIGN AND METHODS WB units were stored for 21 days either at 4°C or 22°C. Half of each temperature group underwent PRT, yielding four final treatment groups (n = 8 each): CON 4 (WB at 4°C); CON 22 (WB at 22°C); PRT 4 (PRT WB at 4°C); and PRT 22 (PRT WB at 22°C). Testing was at baseline, Days 1–7, 10, 14, and 21. Assays included coagulation factors; platelet activation, aggregation, and adhesion; and thromboelastography (TEG). RESULTS Prothrombin time (PT) and partial thromboplastin time increased over time; refrigeration attenuated the effects on PT (p ≤ 0.009). Aggregation decreased over time (p ≤ 0.001); losses were attenuated by refrigeration (p ≤ 0.001). Refrigeration preserved TEG parameters (p ≤ 0.001) and PRT 4 samples remained within normal limits throughout the study. Refrigeration in combination with PRT inhibited fibrinolysis (p ≤ 0.001) and microparticle formation (p ≤ 0.031). Cold storage increased shear-induced platelet aggregation and ristocetin-induced platelet agglutination (p ≥ 0.032), as well as GPIb-expressing platelets (p ≤ 0.009). CONCLUSION The in vitro hemostatic function of WB is largely unaffected by PRT treatment and better preserved by cold storage over 21 days. Refrigerated PRT WB may be suitable for trauma resuscitation. Clinical studies are warranted.

WS granules caused endothelial injury and significant transmural damage to the vessels that render them nonviable for primary surgical repair. The granules can enter systemic circulation and cause distal thrombosis in vital organs. More relevant in vitro and in vivo safety tests should be required for clearance of new hemostatic agents.