Assessment of volume responsiveness during mechanical ventilation: recent advances

Predicting which patients with acute circulatory failure will respond to fluid by a significant increase in cardiac output is a daily challenge, in particular in the setting of the intensive care unit (ICU). This challenge has become even more crucial because evidence is growing that administering excessive amounts of fluid is a risk factor in critically ill patients, in particular in patients with lung injury. However, some tests and indices allow prediction of fluid responsiveness before intravenous fluids are infused. In patients receiving mechanical ventilation, the arterial pulse pressure variation (PPV) has been used for many years. More recently, other tests, which may overcome some limitations of PPV, have been developed. In addition, recent studies have emphasized how the hemodynamic effects of volume expansion should be assessed once fluid has been administered.