Difference in venous-arterial carbon dioxide in septic shock

Determining the venous-to-arterial PCO2 difference (PCO2gap) during resuscitation of septic shock patients might be useful when deciding when to continue resuscitation despite a ScvO2>70% associated with hyperlacticemia. Because hyperlacticemia is not a discriminatory factor in defining the cause of that stress, a PCO2gap>6 mmHg could be used to identify global tissue hypoperfusion. Monitoring the "Gap" could be a useful complementary tool after optimization of O2-derived parameters was achieved to evaluate the adequacy of blood flow to global metabolic demand. In this regard it can help to titrate inotropes in order to adapt O2 delivery to CO2 production, or to choose between haemoglobin correction or fluid/inotrope infusion in patients with a too low ScvO2 related to metabolic demand.