REDUCED OXYGEN-AFFINITY CONTRIBUTES TO IMPROVED OXYGEN RELEASING CAPACITY DURING ERYTHROPOIETIN TREATMENT OF RENAL ANEMIA

In addition to haemoglobin concentration, haemoglobin oxygen affinity plays a major role in the oxygen releasing capacity of the blood. In t his study we have measured oxygen affinity as P50 and calculated the o xygen releasing capacity of blood from 10 haemodialysis patients treat ed with erythropoietin (rHuEpo). The patients were examined with diffe rent assays before start of treatment, after 11 weeks, and after 27 we eks. During the first phase of treatment the oxygen releasing capacity improved because of an increase in the haemoglobin concentration and P50. During the second phase there was a further significant increase in haemoglobin concentration, but due to a decrease in the P50 value t he oxygen releasing capacity remained unchanged. Despite an unchanged oxygen releasing capacity and total blood volume, the antihypertensive treatment had to be increased during that phase of treatment. An incr ease in whole-blood viscosity may explain the increased need of antihy pertensive drugs. The increase in P50 during the first phase of rHuEpo treatment can probably be explained by decreased mean age of the eryt hrocyte population and implies that the beneficial effect is greater t han could be concluded from the increase in haemoglobin concentration.