We aim to test the hypothesis that fluid therapy based on pulse pressure variation (PPV) in patients after cardiac surgery who are mechanically ventilated leads to a significant decrease in the amount of fluid given to such patients in the first 24 hours after surgery

1. The investigators will study patients after cardiac surgery
2. The investigators will collect data on standard care in pre-intervention population
3. The investigators will collect demographic and clinical data
4. The investigators will collect biochemical data in the first 24 hours after surgery
5. The investigators will collect biochemical, physiological and clinical outcome data
6. The investigators will compare the standard care and intervention period data

Inclusion Criteria:

1. immediately after ICU admission after cardiac surgery
2. mandatory mechanical ventilation -

Exclusion Criteria:

1. Pressure support ventilation
2. ECMO
3. Intra-aortic balloon counterpulsation