Static and dynamic preload indicators in multiple organ dysfunction syndrome

In patients with multiple organ dysfunction syndrome, early optimization of cardiac preload is required to improve outcome. This review describes available static and dynamic indices used as bedside indicators of cardiac preload and fluid responsiveness in critically ill patients. Static indices (mostly derived from a pulmonary artery catheter or echocardiography) are based on measurements of cardiac pressures and volumes. Dynamic indices are based on a functional assessment of the pressure–volume relationship and the heart–lung interaction. Available data demonstrated that dynamic indices such as pulse pressure variation and stroke volume variation were more reliable predictors of fluid responsiveness than static indices. Dynamic indices using non-invasive devices are also proposed and it is expected that they will be used more often in future. However, spontaneous breathing movements and arrhythmia are the major limitations to the use of dynamic indices in clinical practice. In this respect, new volumetric bedside assessment methods could represent good alternatives.