Assessment of Fluid Requirements: Fluid Responsiveness

Fluid administration is the first-line therapy in many patients with circulatory failure, though many patients may not respond to it. Accordingly, it is important to determine the chances of the patient responding to fluids. Assessing fluid responsiveness with the dynamic approach is based on the Frank–Starling relationship: using either heart–lung interactions or a postural change, an acute and transient change in preload is obtained, which results in an increase in stroke volume (SV) in preload-dependent patients, while it remains unaltered in preload-independent patients. Static estimates of preload (pressures, surfaces, and volumes) are unfortunately of limited value since each patient is characterized by his or her own Frank–Starling relationship, and so it is difficult to predict the response to fluids from a given value of preload.