Right heart dysfunction remains a frequent cause of morbidity and mortality after cardiac surgery. Respiratory acidosis, particularly when accompanied by hypoxemia, plays a significant role in right heart failure, primarily by increasing right ventricular afterload through pulmonary vasoconstriction and elevated pulmonary arterial pressures. This phenomenon leads to increased right ventricular workload, causing dilation, decreased contractility, and ultimately right heart failure. The study aims to evaluate the effect of respiratory acidosis on right ventricular function after cardiac surgery.

Post hoc analysis of data from two separate studies previously approved by the Research Ethics Board NCT05886413 and NCT06826794. A stratification according to respiratory acidosis defined by a pH <7.35 with PaCO₂ >45mmHg on the first arterial blood gas analysis at the intensive care unit arrival will be done.

Inclusion Criteria:

• Previously included and complete study NCT05886413 or NCT06826794

Exclusion Criteria:

• Absence of one or more of the following hemodynamic measurements: systolic or diastolic pulmonary artery pressure, central venous pressure, cardiac output
• Absence of arterial blood gas on arrival to the intensive care unit

Adult patients who underwent cardiac surgery mechanically ventilated in controlled mode, and had an arterial blood gas within the first hour following admission.