Dynamic Parameters in Evaluation of Fluid Responsiveness

Intravenous infusion of fluids in patients after surgery is a very important part of treatment. However, administering too much or too little fluid can lengthen the stay in the intensive care unit or even harm the patient. Therefore, fluid therapy should be tailored to the individual needs of each patient. Several methods are available to assess which patients will likely benefit from fluid administration. However, each of these methods is useful only under certain conditions. The study aims to explore some less-known, yet promising tests which could make adequate fluid administration more precise and easier to achieve.

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

Eligibility Criteria:
Inclusion Criteria:

* patients after elective coronary artery bypass grafting
* hypovolemia indicated for volumotherapy by the attending physician based on clinical and laboratory signs (ScvO2 under 65 % with serum lactate above 2 mmol/l, increase of vasopressoric support with CVP under 5 mmHg)
* intubated and ventilated patients
* sedation without spontaneous breathing activity
* no pulmonary pathology on X-ray after surgery
* normal systolic and diastolic function of both ventricles (left ventricular ejection fraction above 50 %, TAPSE of the right ventricle above 20 mm, FAC of the right ventricle above 30 %)
* informed consent signed before surgery

Exclusion Criteria:

* aggresive artificial ventilation (PEEP above 10 cmH2O, Pmax above 30 cm H2O)
* ARDS, pneumothorax, fluidothorax
* hemodynamically significant valvular disease
* atrial fibrillation or other arrhythmia with irregular heartbeat
* intraabdominal hypertension with pressures above 15 mmHg
* open thorax
* bad echogenicity