OBJECTIVE The authors evaluated the ability of 2 pulse contour cardiac output (CO) techniques to track CO changes during passive leg raising (PLR) to assess fluid loading responsiveness. METHODS A prospective study. METHODS An intensive care unit in a university hospital. METHODS Twenty mechanically ventilated postoperative cardiac surgery patients. METHODS Thirty-degree PLR. RESULTS The authors estimated CO by 3 techniques: thermodilution (COtd), arterial pulse power (Coli; LiDCO, London, UK), and pulse contour method (Com; FMS, Amsterdam, The Netherlands) based on uncalibrated Modelflow. The authors measured heart rate (HR), central venous pressure, arterial pulse pressure (PP), systolic pressure (SP), and mean arterial pressure (MAP). Stroke volume (SV), SP, PP, and SV variation (PPV and SVV, respectively) were calculated over 5 breaths. SVV was measured by both LiDCO (SVVli) and Modelflow (SVVm) devices. PLR-induced changes in COtd correlated with COli (p < 0.001) and COm (p < 0.001). Preload dependence was predicted with an area under the ROC curve of 0.968 for ΔCOm, 0.841 for ΔCOli, 0.825 for SVVm, 0.873 for SVVli, 0.808 for PPV, 0.778 for ΔSP, 0.714 for ΔPP, and 0.873 for ΔMAP. CONCLUSIONS Changes in COm, COli, SVV, and PPV track COtd changes during PLR with a high degree of accuracy in sedated, ventilated, postoperative cardiac surgery patients. Changes in pulse contour CO after PLR can be used to predict fluid loading responsiveness.