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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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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