Purpose of review: Cardiac preload is frequently altered during hemodynamic failure and is a major focus of therapeutic management. The aim of this review was to summarize the invasive indicators of preload and the invasive predictors of preload responsiveness.
Recent findings: The static assessment of preload is based on the measurement of pulmonary artery occlusion pressure, which is still considered a gold standard. The reliability of the transpulmonary dilution method for bedside monitoring of cardiac volumes and preload has been clearly documented. Nonetheless, a number of recent studies have emphasized the poor value of static markers of preload for predicting a positive response to fluid therapy in comparison to 'dynamic' or 'functional' indices. Among them, the respiratory variation of arterial pulse pressure has been confirmed by numerous studies as an excellent indicator of volume responsiveness. The limitations for using these dynamic parameters have recently been emphasized so that alternative methods, such as passive leg raising or the respiratory systolic variation test, have been developed.
Summary: The best prediction of the hemodynamic response to fluid therapy is afforded by functional evaluation of preload responsiveness rather than by static markers of preload.