Stroke volume variations for assessment of cardiac responsiveness to volume loading in mechanically ventilated patients after cardiac surgery

Objective: We hypothesized that measuring stroke volume variation (SVV) during mechanical ventilation by continuous arterial pulse contour analysis allows the accurate prediction and monitoring of changes in cardiac index (CI) in response to volume administration. Design and setting: Prospective study in an university hospital. Patients: Twenty mechanically ventilated patients following cardiac surgery. Interventions: Volume loading with oxypolygelatin (3.5%) 20 ml x body mass index over 10 min. Measurements and results: SVV, central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP), left ventricular end-diastolic area index (LVEDAI) by transesophageal echocardiography, intrathoracic blood volume index (ITBVI) by transpulmonary thermodilution and CI were determined immediately before and after volume loading. SVV decreased, while CI, CVP, PAOP, ITBVI, and LVEDAI increased significantly. Percentage changes in CI were significantly correlated to percentage changes in SVV (r(2)=-0.59, p<0.001), ITBVI (r(2)=0.79, p<0.001), and PAOP (r(2)=0.33, p<0.05) and to baseline values of SVV (r(2)=0.55, p<0.05) and LVEDAI (r(2)=-0.68, p<0.001). Conclusions: SVV may help to determine the preload condition of ventilated patients following cardiac surgery and to predict and continuously monitor effects of volume administered as part of their hemodynamic management.