The effects of elevated red blood cell 2,3-diphosphoglycerate concentration on myocardial oxygenation and metabolism during cardiopulmonary bypass.

The effects of 2,3-diphosphoglycerate concentration in the red blood cells on myocardial oxygenation, metabolism, and performance were studied in patients subjected to aortic valve replacement. 2,3-DPG increased from 0.90 ± 0.03 to 1.31 ± 0.06 M/M Hb* (from 13.9 ± 0.5 to 20.3 ± 0.9 μmoles/gm Hb) and the standard P50† increased by 4.3 mm Hg in the patients to whom enriched red blood cells were given, whereas there was a slight decrease in 2,3-DPG concentration and no change in the P50 in the control group patients. However, during early reperfusion after ischemia the hemoglobin oxygen saturation of the coronary sinus blood and the arteriovenous oxygen content difference of the heart changed similarly in both patient groups and the coronary sinus blood P o 2 was even higher in the DPG group. On the other hand, the hearts of the patients with high 2,3-DPG concentrations produced less lactate after 5 minutes of reperfusion. There were no such changes or differences in the myocardial performance as assessed by cardiac index, left ventricular stroke work index, and pulmonary capillary wedge pressure which could be considered consequences of the differences in the red blood cell 2,3-DPG concentration. It is concluded that the overall myocardial oxygen extraction after cold ischemia is not improved by providing supranormal 2,3-DPG concentration in red blood cells. This suggests that the reduced oxygen extraction is due to an abnormality in usage of myocardial oxygen rather than an increase in the oxygen affinity of hemoglobin. However, during the immediate postischemia reperfusion there may be underperfused myocardial regions where the better oxygen availability provided by high level of 2,3-DPC leads to a decrease in anaerobic metabolism and lactate production.