Effect of red cell transfusion on oxygen consumption following fluid resuscitation in septic shock

Previous studies have shown that fluid resuscitation in septic shock improves oxygen consumption. Red cell transfusion during resuscitation from septic shock has also been shown to enhance oxygen consumption in patients with elevated lactate levels. This study investigates the effect of increasing oxygen delivery (DO2) through an isolated increase in arterial oxygen content following adequate fluid resuscitation from septic shock in humans. Nineteen patients receiving red cell transfusion (591 +/- 55 SEM ml) were monitored for changes in hemodynamic and oxygen utilization variables before and after transfusion. Transfusion resulted in a significant increase in hemoglobin (8.3 +/- 0.3 to 10.7 +/- 0.3 g.dl-1) and DO2 (483 +/- 29 to 621 +/- 32 ml.min-1.m-2). No increase in cardiac output or pulmonary artery wedge pressure (PAWP) resulted from the transfusion. In spite of the increase in delivery, there was no increase in oxygen consumption (VO2) or decrease in lactate. Subset analysis revealed that a pretransfusion oxygen extraction ratio under 24% was associated with an increase in VO2, but the pretransfusion level of cardiac index, PAWP, lactate, or VO2 was not. An isolated increase in arterial oxygen content as a means of increasing DO2 does not improve VO2 in septic shock following adequate fluid resuscitation. Patients with a low oxygen extraction ratio (less than 24%) represent a subset of patients which did improve consumption with transfusion, and may represent a more severe microcirculatory disturbance not amenable to fluid loading.