Effects of hemodialysis on hemoglobin oxygen affinity and cardiac function.

Background: Hemoglobin affinity for oxygen is modulated by ambient oxygen tension, acid/base status, 2,3 diphosphoglycerate (2,3DPG) concentrations and other factors, facilitating tissue oxygenation under changing conditions. 2,3DPG is a key regulator of oxygen affinity within red blood cells and its levels are affected by blood phosphate. P50, the partial pressure of oxygen at which 50% of its hemoglobin binding sites are occupied, is a marker of oxygen delivery to tissues. We measured P50 during hemodialysis and explored its relationship with mineral metabolites and left ventricular strain as a marker of cardiac function. Methods: Venous blood gas and other laboratory parameters were measured in 20 prevalent patients pre- and post-hemodialysis. To avoid arterio-venous mixing, we selected patients dialyzing through tunneled dialysis catheters. Associations of P50 with demographics, laboratory parameters and echocardiographic measurements were examined using linear regression models. Results: P50 levels decreased from 27.1 ± 0.9 mmHg to 26.2 ± 0.7 mmHg during hemodialysis ( Conclusions: Hemodialysis consistently reduces P50. The magnitude of P50 change was strongly associated with concurrent phosphate changes. P50 reductions correlated with acute lowering of LVGLS. These observations illuminate a potential cause of systemic tissue hypoxia and potential cardiac dysfunction during hemodialysis.