Comparative effects of red blood cell transfusion and increasing blood flow on tissue oxygenation in oxygen supply-dependent conditions

Red blood cell (RBC) transfusion is usually administered to improve oxygen delivery (Do(2)) in order to sustain tissue oxygen demand. However, this pr actice is not supported by firm clinical or experimental data. Using a rand omized two-period crossover design, this study compared the efficacy of "fr esh" RBC transfusion and increased blood flow to restore tissue oxygenation in oxygen supply-dependent conditions. In 12 ketamine-anesthetized mongrel dogs submitted to nonpulsatile normothermic cardiopulmonary bypass, Do(2) was reduced by a progressive decrease in pump flow. Do(2) dependency was de fined as an O-2 uptake ((V) over dot O-2,) decrease by more than 15% from b aseline value. Then, intervention consisted of a 40% increase in Do(2) obta ined either by transfusion of "fresh" dog's RBC (stored < 3 d) or by increa se in pump flow. Animals received both interventions sequentially in a rand om order, while O-2 saturation was maintained constant. In O-2 supply-depen dent conditions, rising pump flow from 1.6 +/- 0.4 to 2.7 +/- 0.7 L/ min in creased Do(2) from 5.4 +/- 1.1 to 9.0 +/- 1.3 ml/kg/min (p < 0.01) and (V) over dot O-2 from 3.5 +/- 0.4 to 4.1 +/- 0.5 ml/kg/min (p = 0.02). "Fresh" RBC transfusion, which increased the hemoglobin concentration from 6.4 +/- 0.9 to 11.1 +/- 1.3 g/dl, increased Do(2) from 5.4 +/- 1.2 to 9.0 +/- 1.4 m l/kg/min (p < 0.01) and (V) over dot O-2, from 3.6 +/- 0.4 to 4.1 +/- 0.5 m l/kg/min (p = 0.02). There was no difference in (V) over dot O-2 resulting from both interventions. In oxygen supply-dependent conditions, "fresh" RBC transfusion and increased blood flow are equally effective in restoring ti ssue oxygenation.