Potassium load in CPD-preserved whole blood and two types of packed red blood cells

The potassium load of transfused blood must be minimized. We have compared the total plasma potassium content of units of CPD-preserved stored whole blood (SWB), stored packed cells (SPC), and packed cells prepared from stored whole blood (WB-PC). Plasma potassium concentrations, unit weights, and hematocrits of 20 units of SWB, 27 units of SPC, and 20 units of WB-PC of various ages were measured. During the 21-day storage period, total plasma potassium content per unit increased in units of SPC at the same rate as in units of SWB, because plasma potassium concentration increased in SPC at three times the rate of SWB. The values for total plasma potassium per unit at 14 and 21 days in mEq/unit were: SWB, 4.4, 5.8; SPC 3.1, 4.4; and WB-PC 1.9, 2.5. Thus, SPC units may contain substantial amounts of plasma potassium when stored for two to three weeks. However, removal of most of the remaining supernatant plasma from SPC units just prior to administration provides a readily available supply of low potassium blood while allowing maximum conservation of scarce blood resources.