In the study by Rivers et al,2 basal hematocrit was almost 35% in both groups, which would argue against transfusion. However, 64.1% of the EGDT subjects received transfusions. This we believe was the consequence of two interacting factors related to the study itself. Firstly, the larger volume of IV fluids received in the EGDT group caused greater hemodilution. Secondly, the intervention protocol dictated Svo2 > 70%. According to the Fick principle, Svo2 varies directly with arterial oxygen saturation, cardiac output, and hemoglobin concentration and inversely with oxygen consumption. Hemodilution-induced decreases in hemoglobin concentration would have had a depressing effect on Svo2. Since blood transfusion is the most energy-efficient way to raise Svo2, more so than the administration of dobutamine, which increases both cardiac output and oxygen consumption, it is not surprising that transfusion became the workhorse with which to achieve Svo2 > 70%. The unanswered issue is whether a transfusion-induced increase in Svo2 is tantamount to improved cellular oxygen utilization. We think not.