Dynamic Parameters in Evaluation of Fluid Responsiveness

Adequate fluid therapy is one of the most important variables influencing patient outcome in intensive care. Fluid therapy should be tailored to the individual needs of each patient. Static parameters of preload have proved to be of little predictive value, therefore dynamic parameters are preferred for prediction of fluid responsiveness. Ideally, the cardiac output increases by 10% after a standardised fluid challenge. There are several methods already available to differentiate fluid-responsive from fluid-unresponsive patients, most notably the passive leg-raise. However, each of these methods has its own set of indications and contraindications. Also, a combination of tests could guide clinician´s decision in cases where the results of a single test are not entirely conclusive. Therefore, it would be desirable to add some less-known methods for prediction of fluid responsiveness, like the end-expiratory and end-inspiratory occlusion tests along with the assessment of diastolic properties of cardiac ventricles. The aims of the study are: * to determine the optimal increase in LVOT VTi to reliably predict fluid responsiveness * to explore the accuracy of echocardiographic LVOT VTi evaluation during end-expiratory and end-inspiratory occlusion tests and their combination * to assess the difference in echocardiographic properties of cardiac ventricles in fluid-responsive and fluid-unresponsive patients * to compare the prediction based on echocardiography with the response to a standardised fluid challenge * to assess the feasibility and practicality of echocardiographic monitoring in anesthetised cardiac surgery patients in intensive care