Fluid Responsiveness Predictability

Personalzing intraoperative anesthetic fluid management may help in preventing fluid accumulation and related complications. Fluids are gine as boluses in operating room (the so-called FC). The response to the FC is due to several physiological conditions related to the "preload dependency" (i.e. the intrinsic ability of the heart of increasing the stroke volume - SV - in response to fluid administration). The minimal volume required to appropriately "challenge" the cardiovascular system is 4 ml/kg of fluid, but higher volumes (up to 6 ml/kg may be needed). Predicting the response to FC administration may be possible by applying a physiological test (called functional hemodynamic test), such as the end-expiratory occlusion test, consisting in interrupping the mechanical ventilation and hence promoting venous return and consequente SV changes. The percentage of SV increase associated to EEOT may predict fluid responsiveness to the FC (patients responders will increase SV to a bigger extent, as compared to non-responders)