Supplementation of Barium to Cold-Stored Platelets Improves Platelet Quality over 7 Days of Storage

Background:

Hemorrhage is responsible for the majority of potentially survivable deaths amongst military and civilian sectors. Early interventions to manage bleeding during hemorrhagic injury, including administration of platelets (PLTs), are crucial for decreasing mortality. Cold-stored PLTs are an attractive treatment for active bleeding as they provide greater functional preservation and a reduced risk of bacterial sepsis than conventional room temperature stored PLTs. However, cold storage causes a rise in PLT intracellular calcium, subsequent activation of signaling pathways, and often results in aggregate formation. In this study, we hypothesized that storing PLTs in the cold with barium, a divalent cation chelated by citrate anticoagulant, would improve PLT quality.

Methods:

Apheresis PLTs in 100% plasma were collected from healthy donors (n=4). Briefly, 10 mL of PLTs were sterilely aliquotted and added to 15 mL mini-bags containing 0- (Control), 3-, or 6-mM BaCl₂. Individual mini-bags were used for each timepoint and condition. Bags were incubated for 15 min at room temperature prior to long-term storage in a walk-in refrigerator (1°-6°C). Samples were assayed on days 1 (the day after collection) and 7 of storage for PLT metabolism, count, clot formation, clot retraction, and activation (phosphatidylserine, mitochondrial depolarization, GPIb, and P-Selectin). Data were reported as means±SD.

Results:

Compared to Control at day 7, BaCl₂-treated bags exhibited higher PLT counts (Control: 422±215 x10³ PLTs/µL; 3 mM BaCl₂: 468±222 x10³ PLTs/µL; 6 mM BaCl₂: 697±194 x10³ PLTs/µL), less PS exposure (Control: 6.3±3.5%; 3 mM BaCl₂: 5.8±3 %; 6 mM BaCl₂: 5.6±2.8 %), and less mitochondrial membrane depolarization. Additionally, glucose consumption and lactate production were lower in barium-supplemented PLTs. GPIb expression and P-Selectin was comparable amongst all groups. Hemostatic function, as assessed via thromboelastography and clot retraction, was not negatively affected by addition of BaCl₂. In most assays, cold storage of PLTs with the higher concentration of BaCl₂ (6 mM) seemed to confer the greatest advantages.

Conclusion:

Supplementation of barium to PLTs provides a promising avenue for transfusion medicine since PLT count is better preserved and activation is decreased compared to normal refrigerated storage. Future studies are warranted to determine the effects of barium supplementation on other aspects of cold-stored PLT function (e.g. procoagulant activity and PLT adhesion under physiologic flow) and with respect to alternate storage media (e.g. PLT additive solutions).