What is the role of measuring effective oxygen delivery and organ blood flow in the treatment for sepsis/septic shock?

Updated: Oct 07, 2020
  • Author: Andre Kalil, MD, MPH; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

Although not part of the guidelines, much attention to measuring not only effective oxygen delivery but also organ blood flow has emerged as reasonable parameters to grade shock severity. Clearly, a low ScvO2 can occur from reduced cardiac output, but it can also occur from severe anemia (or hemoglobinopathies) and hypoxemia. Similarly, a normal or high ScvO2 may reflect metabolic block, shunt, or sampling errors.

To address many of these errors one should calculate the arterial–to–central venous PO2 gradient (Pa-vO2). Since viable tissues produce carbon dioxide as an endpoint of metabolism, end-capillary PCO2 increases as tissue blood flow decreases. The central venous–to–arterial PCO2 gap (Pv-aCO2) assesses blood flow. Finally, lactate, although insensitive as a marker of ischemia, is still an excellent measure of tissue injury and the inflammatory state. Thus, the Pv-aCO2/Pa-vO2 ratio can be used to assess the severity of circulatory shock in sepsis. [77, 78]


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