Study design
After inclusion (Baseline 1), we collected the hemodynamic variables, including heart rate, arterial pressure including pulse pressure (PP), PPV, SVV, central venous pressure, intra-abdominal pressure (IAP), ventilatory parameters, and cardiac index (CI) measured by transpulmonary thermodilution.Volume responsiveness was assessed by a 1-min PLR-test [Then, we performed the PEEP-test by reducing PEEP from its baseline level (≥ 10 cmHIn volume responsive patients, and when deemed necessary by the clinicians in charge, fluid bolus (500 mL of normal saline) was administered. In such cases, transpulmonary thermodilution measurements were performed immediately after fluid administration.Continuous hemodynamic variables, including pulse contour analysis-derived CI, were recorded using PiCCOWin 4.0 software (Pulsion Medical Systems, Feldkirchen, Germany).