title: Effect of cold storage on shear-induced platelet aggregation and clot strength.
abstract: BACKGROUND
  Platelets (PLTs) participate in hemostasis and save lives following trauma. PLTs for transfusion are maintained at room temperature (RT, 22°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°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°C for 5 days, and PLT aggregation and clot strength were assessed at 37°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°C-stored samples on Day 5 compared with fresh or RT-stored samples at all shear rates tested (fresh vs. 4°C and RT vs. 4°C, p < 0.05). PLTs stored at 4°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°C and RT vs. 4°C, p < 0.05).
  
  
  CONCLUSIONS
  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.
authors.affiliation: From the Department of Biomedical Engineering (P.M.N., A.K.R.), The University of Texas at San Antonio; and Blood Research Program (H.F.P., A.P.C.), US Army Institute of Surgical Research, Fort Sam Houston, San Antonia, Texas.
authors.forename: Prajeeda M
authors.initials: PM
authors.lastname: Nair
authors.forename: Heather F
authors.initials: HF
authors.lastname: Pidcoke
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Cap
authors.forename: Anand K
authors.initials: AK
authors.lastname: Ramasubramanian
mesh_terms: D001777:Blood Coagulation; D001792:Blood Platelets / Q000502:physiology*; D001793:Blood Preservation / Q000379:methods*; D003080:Cold Temperature; D006801:Humans; D009391:Nephelometry and Turbidimetry; D010974:Platelet Aggregation; D053657:Platelet-Rich Plasma / Q000502:physiology; D013997:Time Factors