ScVO2 and Lactate..

Central lines terminating in the superior vena cava (i.e. internal jugular and subclavian placement) can also be used to determine the central venous oxygenation (ScvO2), as part of the EGDT protocol.

 

An ScvO2 of less than 70% would be an indicator that oxygen delivery to tissues is not matching the demand, and that further interventions are needed such as

 

1) Intubation to increase PaO2,

  2) Blood transfusion to achieve a Hct of ≥ 30%,

3) Initiation of an inotrope, usually Dobutamine.

 

While ScvO2 was shown to correlate with mixed venous oxygenation SvO2 obtained from a pulmonary artery catheter, peripheral venous blood gases (VBG) are not good indicators of systemic oxygen extraction.

Lactic acid has recently gained interest as a possible substitute for ScvO2 to determine adequate delivery of oxygen to tissues. A study by Jones et al has shown that a lactic acid clearance of more than 10% at least two hours after adequate fluid resuscitation was non inferior to an ScvO2 goal of ≥70%. Lactic acid can therefore be used in place of ScvO2, with the advantage that it can be easily drawn from a peripheral vein.

Jones AE, Shapiro NI, Trzeciak S, et al. Lactate clearance vs central venous oxygen saturation as goals of early sepsis therapy: a randomized clinical trial. JAMA. 2010;303(8):739–746.