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

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, pCO(2) pO(2), 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.