Decreased 2,3-Diphosphoglycerate Concentration in Low Cardiac Output Patients and Its Influence on the Determination of In Vivo P50

: We investigated whether 2,3‐diphosphoglycerate (2,3‐DPG) is altered in patients with low cardiac output and the influence of its concentration on the calculation of in vivo P50. Biochemical and blood gas analysis were performed along with the measurement of cardiac output and body temperature in 13 patients submitted to cardiopulmonary bypass surgeries without the use of donor blood. In vivo P50 was calculated using the measured (P50m) and the estimated 2,3‐DPG (P50e). 2,3‐DPG concentration was lower in these patients when compared to the values obtained in normal volunteers (6.9 ± 2.2 vs. 11.9 ± 2.4 μmol/gHb). P50m was lower than P50e (21.6 ± 1.1 vs. 30.1 ± 1.2 mm Hg) at all time points. Our data show that in patients with low cardiac output, 2,3‐DPG concentration is reduced. Therefore, in these patients, the use of standard values for this variable may introduce an error in the calculation of in vivo P50.