Hemodynamic oxygen transport and 2,3-diphosphoglycerate changes after transfusion of patients in acute respiratory failure

Abstract

The goals of management of patients with respiratory failure include improving arterial oxygenation with PEEP and red cell transfusion to maintain oxygen carrying capacity, both of which contribute to improving tissue oxygen delivery. However, standard CPD-stored blood is rapidly depleted of 2,3 diphosphoglycerate (2,3 DPG) and ATP, with resultant inadequacy of the red cell oxygen transport function. In 15 patients requiring mechanical ventilation with PEEP whose initial Hct≤35%, we studied the effect of transfusion of 7 ml/kg of CPD-stored packed red blood cells on hemodynamic and oxygen delivery variables, pulmonary venous admixture (Q_A/Q_T), and erythrocytic P₅₀, 2,3 DPG and ATP concentrations. Hemodynamics were not significantly altered by transfusion. 2,3 DPG decreased significantly from 14.5±1.1 to 13.1±1.5 mcmol/g Hb (mean±SD, p<0.05). There was no significant change in P₅₀ or ATP. Q_A/Q_T rose significantly, from 20.1±7.8 to 28.9±12.3% (mean±SD, p<0.02). In our patients, an increase in arterial oxygen content obtained by transfusion was not followed by any associated decrease in cardiac work, as implied by solution of equations for oxygen delivery and oxygen consumption. The rise in Q_A/Q_T is undesirable in patients requiring PEEP, since it complicates management of their mechanical ventilatory support.