Is the stability of the oxyhaemoglobin dissociation curve in stored blood a function of the way the cells 'pack'?

The results in this report show that the oxyhaemoglobin dissociation curve (ODC) of blood when stored at 4 degrees C under special storage conditions was stable for at least 7 days. The stability of the ODC was reflected in both the haemoglobin p50 (the partial pressure of oxygen at 50% saturation of the haemoglobin) and n (the Hill slope of the ODC) values and was associated with constant blood pH and 2,3-diphosphoglyceric acid (2,3-DPG) concentrations. The ODC was stable whether heparin, ethylene diamine tetra-acetic acid (EDTA) or citrate phosphate dextrose (CPD) were used as anticoagulants, but the latter was associated with higher p50 values than those observed in fresh samples. The most critical storage requirement for the ODC stability appeared to be some function of the area of the cell-plasma interface as orientation of the collection tubes in other than a vertical position, or storing blood in larger containers, resulted in a marked fall in p50. These results have important implications in that they suggest that the relative packing of the cells or cell-cell and/or cell-plasma interfaces can significantly affect the ODC stability. Further, they may be of potential importance in blood banking practice.