A comparative study of reducing the extracellular potassium concentration in red blood cells by washing and by reduction of additive solution

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Extracellular potassium concentration (K+) increases in the supernatant of whole and packed red blood cell units (p RBCs) with duration of refrigerated storage in citrate-phosphate-dextrose-adenine (CPDA-1) and additive solution (AS). Studies have shown that to avoid hyperkalemia, washed p RBCs are preferred if relatively fresh p RBCs are not available. To determine whether a simpler procedure, AS reduction, results in lowering of K+ in p RBCs comparable to that achieved by washing, the K+ levels by both methods were compared.


Pre- and post-K+ levels were measured in 6 washed and 11 AS-reduced p RBC units. Each unit was weighed, hematocrit was determined, K+ was measured, and total K+ was calculated. Washed units were 3 to 21 and AS-reduced units were 4 to 30 days old. Statistical analysis was performed with a t test.


There was no significant difference (p > 0.35) in the initial K+ between the two groups (mean ± SD, 36.95 ± 13.16 m Eq/L before washing and 39.78 ± 19.94 m Eq/L before AS reduction). Washing and AS reduction both led to a significant decrease in K+ levels (2.15 ± 0.10 m Eq/L after washing and 4.41 ± 3.04 m Eq/L after AS reduction, each p < 0.0005). Washing, however, was significantly better than AS reduction in reducing K+ in stored p RBCs (p < 0.05).


Washing p RBCs results in very low levels of K+. AS reduction also significantly reduces K+ levels. Selection of the method of K+ reduction will depend on the stringency of K+ reduction needed, the time constraints, and the availability of facilities and staff for washing.

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