The pursuit of a high central venous oxygen saturation in sepsis: growing concerns

Many physicians believe that global hypoxia secondary to inadequate oxygen delivery (DO2) is responsible for organ failure during severe sepsis. Others believe that sepsis is an inflammatory condition in which abnormalities of DO2 are uncommon. The relative importance of each of these hypotheses, and indeed whether other unknown factors play a role, is simply not known. The issue of DO2 and oxygen consumption in sepsis is highlighted in the paper by van Beest and colleagues [1] in this edition of Critical Care. These authors have focused on central venous oxygen saturation (ScvO2) as a marker of systemic oxygenation. They have done this partly in response to the following fashionable, but yet untested, concepts: first, ScvO2 is a reliable marker of global tissue hypoxia; second, increasing ScvO2 by early goal directed therapy (EGDT) [2] improves outcome; and third, we should follow the Surviving Sepsis Campaign Guidelines [3] by pursuing a SvcO2 > 70% in septic patients. Their findings suggest that the passive acceptance of the above conceptual triad may be unwise. Only 6% of septic patients in their study had a SvcO2 below physiological normality. The mean ScvO2 was 74%, compared to 48.9% in the EGDT study. Certainly, the Dutch patients were different to those in the EGDT study in several important respects: only half were admitted from the emergency department, and many must have received intravenous fluid prior to their intensive care unit (ICU) admission. Despite comparable APACHE II scores, mortality of septic patients in the Dutch study (26%) was much less than in the EGDT standard care arm (46.5%), and less even than in the intervention arm (30%) of that trial. Septic patients presenting to a Dutch ICU would, therefore, be expected to derive no benefit from EGDT-style attempts to increase their (already normal) ScvO2.These observations raise provocative questions about the utility of applying the principles of EGDT outside the single US urban hospital in whic