Use of CO 2 -Derived Variables in Cardiac Intensive Care Unit: Pathophysiology and Clinical Implications.

Shock is a life-threatening condition, and its timely recognition is essential for adequate management. Pediatric patients with congenital heart disease admitted to a cardiac intensive care unit (CICU) after surgical corrections are particularly at risk of low cardiac output syndrome (LCOS) and shock. Blood lactate levels and venous oxygen saturation (ScVO 2 ) are usually used as shock biomarkers to monitor the efficacy of resuscitation efforts, but they are plagued by some limitations. Carbon dioxide (CO 2 )-derived parameters, namely veno-arterial CO 2 difference (ΔCCO 2 ) and the VCO 2 /VO 2 ratio, may represent a potentially valuable addition as sensitive biomarkers to assess tissue perfusion and cellular oxygenation and may represent a valuable addition in shock monitoring. These variables have been mostly studied in the adult population, with a strong association between ΔCCO 2 or VCO 2 /VO 2 ratio and mortality. In children, particularly in CICU, few studies looked at these parameters, while they reported promising results on the use of CO 2 -derived indices for patients' management after cardiac surgeries. This review focuses on the physiological and pathophysiological determinants of ΔCCO 2 and VCO 2 /VO 2 ratio while summarizing the actual state of knowledge on the use of CO 2 -derived indices as hemodynamical markers in CICU.