In septic critically ill mechanically ventilated patients with acute circulatory failure, inadequate volume resuscitation leads to multiple organ failure. Early goal-directed therapy emphasizes early and aggressive hemodynamic support in patients with severe sepsis and septic shock. On the other hand, because of increased microvascular permeability and capillary leakage, conservative fluid management and more aggressive restriction in fluid accumulation to reduce lung water and tissue edema has been suggested by acute respiratory distress syndrome net. Fluid responsiveness refers to the ability of the heart to increase its stroke volume in response to volume load. Accurately predicting volume responsiveness will be beneficial in obviating the need for unnecessary fluid loading, and in detecting patients who may benefit from a volume load.