EVALUATION OF OXYGEN AVAILABILITY WITH OXYGEN STATUS ALGORITHM IN PATIENTS UNDERGOING OPEN-HEART-SURGERY TREATED WITH EPOETIN-BETA

We evaluated in a double-blind randomized study the effect of epoetin beta (recombinant human erythropoietin) therapy on oxygen status in pa tients undergoing cardiac surgery who were contraindicated for autolog ous blood donation. All 76 patients enrolled in this study were random ized to the two treatment groups (5 x 500 U epoetin beta or placebo/kg body weight intravenously over a 14-day period before surgery) and re ceived 300 mg Fe2+ per day orally before surgery. Before and after sur gery the lactate level and the following parameters according to the o xygen status algorithm by Siggaard-Andersen were evaluated: arterial o xygen tension (PaO2), effective hemoglobin concentration (ceHb), arter ial oxygen saturation (SaO(2)), oxygen half saturation tension (p50), red cell 2.3 diphosphoglycerate (2.3 DPG), arterial total oxygen conce ntration (ctO(2)), concentration of extractable oxygen (ex), and oxyge n compensation factor (Qx). Therapy with epoetin beta led to increases in ceHb, PaO2, ctO(2), and ex and to a decrease in Qx before surgery (p < 0.05 for PaO2, p < 0.0001 for the other parameters vs placebo). T he ex in patients who received epoetin beta rose by approximately 20%, thus indicating a considerable improvement in O-2 delivery. In patien ts receiving placebo the hemoximetric parameters remained outside the normal limits at all times after surgery, but in the epoetin beta grou p PaO2, ctO(2), ex, and Qx returned almost to their baseline values by the second or fifth postoperative day, even though the frequency of t ransfusions was significantly higher in the placebo group. Whereas p50 and 2.3 DPG fell in the placebo group after surgery, these two parame ters were significantly higher in the epoetin beta group and led to a further increase in ex (from 24% to 38%) versus the placebo group as a result of the right shift in the hemoglobin O-2-binding curve. The po stoperative incidence and severity of lactic acidosis were higher in t he placebo group. Preoperative epoetin beta therapy is a safe way of p roviding increased extractable O-2 (by 24% to 38%) and decreasing the risk of lactic acidosis after surgery. This therapy has a more favorab le effect on the O-2 binding curve than the transfusion of erythrocyte concentrate and enhances the effect of epoetin beta therapy on the po stoperative oxygen status.