A possible role for the venous-to-arterial CO2 difference in cardiogenic shock: an exploratory study

The venous-to-arterial CO2 partial pressure difference (CO2) is a marker of how adequately capillary blood flow is able to remove CO2 from tissues, but evidence regarding its usefulness in patients with cardiogenic shock (CS) is scarce The main objective of this study was to describe the changes in CO2 in patients with cardiogenic shock during the 48 hours after hospital admission. A secondary objective was to analyze the association between CO2 and in-hospital mortality due to cardiovascular disease (CVD) and cardiogenic shock refractory to treatment.

Prospective observational exploratory study in a single hospital. Patients in cardiogenic shock who were admitted to a cardiology critical care unit were included. We measured CO2 on inclusion and 6, 12, 24, and 48 hours after admission to the unit. Variables were explored with logistic regression analysis and areas under the receiver operating characteristic curves were calculated.

A total of 50 patients were included. In-hospital mortality due to CVD was 20%. CO2 peaked initially and decreased gradually over the first 48 hours of care. In-hospital mortality tended to be higher in patients with the highest CO2 values, but the difference was not significant. High CO2 values at 24 hours were associated with refractory cardiogenic shock. The negative predictive value of a CO2 value lower than 6 mmHg at 12 hours was 87% for mortality due to CVD.

This exploratory study suggests that CO2 could be a helpful additional marker to measure when managing cardiogenic shock. CO2 lower than 6 mmHg between 12 and 24 hours after admission may identify patients at low risk of death due to CVD or refractory cardiogenic shock.