Resuscitation of patients with septic shock: please “mind the gap”!

Excerpt

Van Beest et al. [1] performed a post hoc analysis of 53 patients with severe sepsis or septic shock to investigate the interchangeability of mixed and central venous-to-arterial carbon dioxide (CO₂) differences (mvaCO₂gap and cvaCO₂gap, respectively) and the relation between the cvaCO₂gap (“pCO₂gap” or the “gap”), cardiac index (CI), and outcome. The authors observed a strong agreement between pCO₂ measured from either mixed venous or central venous sites with relatively small limits of agreement. The authors claim that combining ScvO₂ values, as easily obtained from a central venous catheter, as a surrogate for global tissue hypoxia, and pCO₂gap as a surrogate for CI, obtained from the same central venous catheter, may be useful in assessing cardiovascular state during resuscitation in critically ill patients. We cannot agree more and propose thereafter a tentative “ScvO₂-cvaCO₂gap-guided protocol” (Fig. 1). Cuschieri et al. [2] previously demonstrated in a mixed population of critically ill patients that the relationships between the mvaCO₂gap or the cvaCO₂gap and the CI were equivalent. Since central venous blood is readily available from a central venous catheter, whereas mixed venous blood requires a pulmonary artery catheter, the cvaCO₂gap, as an easily available clinical monitoring tool, is attractive. At ICU admission, 24 patients in the van Beest et al. study had a pCO₂gap greater than 0.8 kPa (or 6 mmHg). Persistence of such a large pCO₂gap after 24 h of treatment was predictive of higher mortality.

…