Severe Sepsis and Septic Shock

We would like to address two potentially confusing issues concerning venous oxygen saturation (Svo2) as presented in Table 1 of the review by Angus and van der Poll (Aug. 29 issue).1 First, Table 1 suggests that Svo2 is raised in “sepsis, severe sepsis, and septic shock.” Depending on the timing of patient presentation and the type of sepsis and septic shock, Svo2 may indeed be elevated as a result of microcirculatory shunting or mitochondrial dysfunction. However, in septic shock, Svo2 can be depressed, reflecting an increase in the extraction of oxygen due to a decrease in cardiac output.2-4 Timely treatment to increase low Svo2 values in adults and children may improve outcomes2,3 and has therefore been added to current guidelines for the treatment of sepsis.5 Second, Table 1 indicates that higher Svo2 levels (70 to 80%) are normal in children. As pediatric intensivists, we wish to point out that the opposite may be true in children with sepsis, since their cardiac output is more often decreased rather than increased.3,4 This effect compromises oxygen delivery and decreases Svo2 levels.4