IMPORTANCE OF OXYGEN-HEMOGLOBIN BINDING TO OXYGEN-TRANSPORT IN CONGESTIVE-HEART-FAILURE

Objective-To assess the importance of 2,3-diphosphoglycerate (2,3-DPG) and oxygen-haemoglobin binding to oxygen transport in patients with c ongestive heart failure. Methods-In 30 patients with severe congestive heart failure, arterial, mixed venous, and coronary sinus venous bloo d concentrations of 2,3-DPG were measured and systemic output and coro nary sinus blood flow were measured by a thermodilution technique. Oxy gen-haemoglobin affinity was expressed as the oxygen tension in mm Hg at which blood is 50% saturated with oxygen (P50). Results-Compared wi th normal values, 2,3-DPG was high in arterial blood (2.58 mumol/ml, p = 0.01; 20.8 mumol/g haemoblobin, p < 0.0001). Significant gradients between arterial, mixed venous, and coronary sinus blood 2,3-DPG conce ntrations were also found (mixed venous = 2.40 mumol/ml, p = 0.05 v ar terial blood; coronary sinus venous blood = 2.23 mumol/ml, p < 0.04 v arterial blood). P50 was correspondingly high compared with the accept ed normal value (mean 29.7 mm Hg, normal 26.6 mm Hg, p < 0.001). Syste mic oxygen transport (351 ml O2/min/m2) varied directly with the forwa rd cardiac index (r = 0.89, p < 0.0001). There was no relation between systemic oxygen transport and arterial oxygen content. Similarly, myo cardial oxygen transport was found to vary directly with coronary sinu s blood flow. Calculations of changes in cardiac index and coronary si nus blood flow at normal oxygen-haemoglobin binding indicate that a co nsiderable increase in cardiac index and coronary blood flow would be required to maintain similar systemic and myocardial oxygen transport. Conclusions-In patients with severe heart failure increased 2,3-DPG a nd reduced oxygen-haemoglobin binding may be compensatory mechanisms t hat maintain adequate systemic and delivery of oxygen to myocardial ti ssue.