High veno-arterial carbon dioxide gradient is not predictive of worst outcome after an elective cardiac surgery: a retrospective cohort study.

Alteration of tissue perfusion is a main contributor of organ dysfunction. In cardiac surgery, the importance of organ dysfunction is associated with worse outcome. Central venous-arterial difference in CO ₂ tension (ΔCO ₂ ) has been proposed as a global marker of the adequacy of tissue perfusion in shock states. We hypothesized that ΔCO ₂ could be increased in case of postoperative organ failure or worse outcome. In this monocentric retrospective cohort study, we retrieved, from our database, 220 consecutive patients admitted in intensive care after an elective cardiac surgery. Four time points were formed: ICU admission, and 6, 24 and 48 h after. A ΔCO ₂ below 6 mmHg defined the normal range values. The SOFA score, intensive care unit and hospital length of stay, hospital and 6-month mortality rate were recorded. We compared patient with low ΔCO ₂ (<6 mmHg) and high ΔCO ₂ (≥6 mmHg). We included 55 (25 %) and 165 patients in low and high ΔCO ₂ groups, respectively. The SOFA score, the hospital and 6 months mortality rate were higher in patients with low ΔCO ₂ . Surprisingly, we did not find results previously published in other surgical settings. In cardiac surgery, ΔCO ₂ has a low predictive value of outcome.