Hemoglobin function and 2,3-DPG levels of blood stored at 4 C in ACD and CPD: pH effect.

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Normal hemoglobin function depends on adequate erythrocyte levels of 2,3‐diphosphoglycerate (2,3‐DPG), a compound which is poorly maintained in acid‐citrate‐dextrose (ACD). Since 2,3‐DPG is better maintained in citrate‐phosphate‐dextrose (CPD) and this preservative has a higher pH (5.5) than ACD (pH = 5.0), these preservatives were prepared at each pH and studied. The CPD preservatives (pH 5.0, 5.5) had similar amounts of phosphate so the differences between them, obtained by altering the buffer ratio, should relate to pH. The ACD solutions (pH 5.0, 5.5) contained no phosphate. Hemoglobin function, expressed as P50 (the Po2 at 50 per cent oxygenation, an inverse but direct measure of oxygen affinity), and 2,3‐DPG were better maintained in ACD and CPD of pH 5.5. The lower pH (5.0) preservatives, whether ACD or CPD, showed rapidly declining hemoglobin function and 2,3‐DPG levels. The values at the higher pH remained close to normal for two weeks and above those of the lower pH preservatives for most of the four‐week storage period.