Red Blood Cell Transfusion Improves Perfusion Parameters in Septic Shock Patients With Hypoperfusion

The purpose of this study was to evaluate the immediate effects of red blood cells transfusion on central venous oxygen saturation and lactate levels in septic shock patients randomized to two different hemoglobin levels. The influence of red blood cell (RBC) transfusion on the adequacy of oxygen delivery (DO2) and supply (VO2) could be assessed by systemic oxygen variables such as central venous oxygen saturation (ScvO2) and lactate levels. Although it is not clear that alterations in these parameters actually represent an improvement in the DO2/VO2 ratio, they might represent a better transfusion trigger than the absolute hemoglobin value. Patients admitted with a diagnosis of septic shock and hemoglobin levels lower than 9.0 g/dL , less than 48 hours of shock diagnosis, were included, a central venous catheter in the superior vena cava and signed informed consent. The investigators randomized all patients into two groups. Patients in the liberal group received transfusions immediately, as the objective was to maintain hemoglobin levels above 9.0 g/dL. In the restrictive group, transfusion was withheld until their hemoglobin levels fell below 7.0 g/dL. Each time a patient received a transfusion, the investigators collected a set of laboratory tests, including hemoglobin levels, ScvO2 and lactate, at two time points, immediately before transfusion and one hour after its ending. The sample size was calculated by considering that in 80% of the transfusions in patients in the restrictive group ScvO2 would improve compared to only 45% of those in the liberal group, with an alpha error of 0.05 and 80% power. Improvement was defined as an increase of 5% over the pre-transfusion ScvO2. Twenty-eight transfusions in each group would be necessary, but to correct for potential non-parametric distribution of the main variables, the number was adjusted to 35 transfusions in each group. Trends in ScvO2 and lactate were categorized as worsening or improving. The investigator