Hemoglobin-oxygen affinity in anemia.

In blood of 21 anemic patients and 8 normal subjects (N) three oxygen dissociation curves each were measured at different pH values to calculate Bohr coefficients after acidification with CO2 (BCCO2) or fixed acid (BCFA), and other important parameters of oxygen affinity. The patients had either low hemoglobin or red cell production (L: n = 11, 7.3 g/dl Hb) or high erythrocyte production combined with high loss (H: n = 10, 7.8 g/dl Hb). The standard half saturation pressure P50 (pH 7.4, 37 degrees C) was equally elevated in both anemic groups (L: 30.5, H: 30.8, N: 26.7 mmHg), as well as the diphosphoglycerate concentration (DPG) (L: 18.7, H: 18.6, N: 12.7 mumol/g Hb). The red cell pH of the anemics was lower than for the N (approximately 0.045 units) causing part of the difference in P50. Hill's "n" tended to high values in the anemics except at low O2-saturation in the H. For BCCO2 no significant difference among the groups was observed. BCFA, however, increased in the H at low SO2 compared to the N and L. The cause for most of the changes in hemoglobin oxygen affinity in anemics was the high [DPG]. The combination of high P50 and high "n" value as in the L seems to be most advantageous for tissue oxygenation.