Storage of platelets in additive solutions: effects of magnesium and/or potassium

Abstract

BACKGROUND: Previous studies indicate that platelet concentrates (PCs) in a platelet additive solution (PAS) containing citrate, acetate, and sodium chloride (PAS‐2) show a significantly higher increase of CD62+ platelets than PCs in other brands of PAS containing Mg²⁺ and K⁺. To investigate whether this difference can be explained by the presence of Mg²⁺ and/or K⁺ in the storage medium, we performed paired studies comparing storage of PCs in PAS‐2 to PAS‐2 with either Mg²⁺ or K⁺ or both in combination. STUDY DESIGN AND METHODS: PCs from pooled buffy coats were prepared in either PAS‐2 or PAS‐2 with Mg²⁺ or K⁺ or both in combination (PAS‐2 modified). Different volumes of MgCl₂ solution (1 mol/L) and/or KCl solution (1 mol/L) were added to PAS‐2 to obtain various concentrations. After preparation and during storage (at Days 3 and 7), pH, pCO₂, pO₂, HCO₃⁻, and CD62 (%) were measured. RESULTS: During 7 days of storage, pH was very stable (6.9‐7.2) in all PCs. At Day 7, platelet CD62 expression was 49 percent (PAS‐2), 41 percent (PAS‐2 with 1.5 mmol/L Mg²⁺), and 38 percent (PAS‐2 with 4.5 mmol/L Mg²⁺). With added K⁺, at Day 7, expression of CD62 was 55 percent (PAS‐2), 39 percent (PAS‐2 with 4.5 mmol/L K⁺), and 35 percent (PAS‐2 with 9.0 mmol/L K⁺). In PAS‐2 modified (PAS‐2 with 1.5 mmol/L Mg²⁺ and 4.5 mmol/L K⁺) and CPD plasma, the corresponding CD62 values were 23 and 35 percent, respectively. CONCLUSION: The combination of Mg²⁺ and K⁺ gave significantly (p < 0.05) lower platelet CD62 expression in the storage medium than in PAS‐2. The effects of these differences on platelet metabolism and in vivo properties remain to be investigated.