This study uses the portal vein pulsatility index (PVPI) to assess fluid intolerance amongst fluid responders.

This prospective observational study aims to use the portal vein pulsatility index (PVPI) to assess fluid intolerance in fluid responders. The investigators will enroll mechanically ventilated postoperative adult patients within 6 hours of ICU admission after cardiac surgery. Patients will undergo a Passive Leg Raising (PLR) test and Left Ventricular Outflow Tract (LVOT) recording using transthoracic echocardiography. The main objective is to predict fluid intolerance after a fluid challenge of 7 ml/kg Ringer Lactate over 10 minutes in initially tolerant fluid responders.

Inclusion Criteria:

• Informed consent.
• Mechanically ventilated patients within 6 hours after ICU admission following surgery who are considered for fluid administration to optimize haemodynamics.
• Sinus rhythm.

Exclusion Criteria:

• A condition known to interfere with portal vein flow assessment or interpretation (liver cirrhosis or chronic hepatic disease, suprahepatic or portal vein thrombosis).
• Any mechanical circulatory support.
• Cardiac transplant.
• Poor transthoracic echocardiographic window.

Mechanically ventilated postoperative adult patients after cardiac surgery within 6 hours after intensive care unit admission.