Effect of cold storage on shear-induced platelet aggregation and clot strength

BACKGROUND: Platelets (PLTs) participate in hemostasis and save lives following trauma. PLTs for transfusion are maintained at room temperature (RT, 22 degrees C), limiting viability to 5 days because of metabolic compromise and high risk of bacterial contamination. RT storage may result in weaker clots, delaying hemorrhage control, whereas cold storage (4 degrees C) could permit longer PLT shelf life and result in a more hemostatic product. In this study, we characterized the effect of storage temperature on shear-induced PLT aggregation, clot formation, and strength. METHODS: PLTs obtained from phlebotomized blood or by apheresis were stored at RT or 4 degrees C for 5 days, and PLT aggregation and clot strength were assessed at 37 degrees C. We studied PLT aggregation at steady and complex patterns of shear rates (500-2,500 per second) by flow cytometry, and the kinetics of clot formation and strength were measured using turbidity and dynamic mechanical analysis, respectively. RESULTS: PLT aggregation was higher in 4 degrees C-stored samples on Day 5 compared with fresh or RT-stored samples at all shear rates tested (fresh vs. 4 degrees C and RT vs. 4 degrees C, p < 0.05). PLTs stored at 4 degrees C for 5 days formed significantly stronger clots compared with fresh or RT-stored samples as quantified by turbidity and elastic moduli measurements (fresh vs. 4 degrees C and RT vs. 4 degrees C, p < 0.05). CONCLUSION: Our results show that cold-stored PLTs are more responsive to aggregation stimuli and form stronger clots, presumably because of thicker fibrin strands. These data suggest that the superior functionality of cold-stored PLTs may support faster hemostasis for acutely bleeding in trauma patients compared with RT-stored PLTs. (J Trauma Acute Care Surg. 2014; 77: S88-S93. Copyright (C) 2014 by Lippincott Williams & Wilkins)