Fluid Management Surgical Patients in Intensive Care Unit.

Inclusion Criteria: * Patients who are admitted to the intensive care unit of National Hepatology \& Tropical Medicine Research Institute (NHTMRI) post intra-abdominal surgical intervention. Exclusion Criteria: * Patients will be excluded from the study if they have severe liver impairment (child-Pugh C15), septic shock or hemodynamic instability requiring high dose circulatory support e.g. \> 2ug/min noradrenaline as it will impair lactate clearance \&/or central venous oxygen saturation normalization, advanced heart failure, central venous pressure (CVP) ≥ 18cmH2O as it will limit fluid therapy, severe hypothermia (\< 28◦ C) as it will induce lactate production.