Purpose of review: In the ICU only half of the patients are volume responsive – that is, they respond to fluid administration by increasing their cardiac output. We aim to summarize the methods available for predicting volume responsiveness, focusing on recent findings in patients with spontaneous breathing activity.
Recent findings: New information mainly comes from studies that have attempted to find accurate predictors of volume responsiveness in cases of spontaneous breathing activity when heart–lung interaction indices cannot be reliably used. Passive leg raising has emerged as a reliable test for this purpose. The hemodynamic response to this maneuver, which induces a transient increase in cardiac preload, has been shown to provide a robust prediction of volume responsiveness. Assessment of the effects of passive leg raising requires real-time measurement of cardiac output/stroke volume or their surrogates.
Summary: Predicting the hemodynamic response to fluid administration in patients with acute circulatory failure is of major importance and numerous methods are now available. While the respiratory variations of stroke volume (or its surrogates) can be used in patients fully adapted to their ventilator, the passive leg-raising test has become a reliable predictive method in patients with spontaneous breathing activity.