The role of point-of-care ultrasound to assess fluid responsiveness and fluid tolerance in the intensive care unit

Fluid accumulation is epidemiologically associated with adverse outcomes in various clinical contexts. Assessing fluid responsiveness identifies conditions where intravenous fluids can increase cardiac output, improve organ blood supply during hypoperfusion and prevent the administration of ineffective fluids with deleterious effects. Point-of-care ultrasound (POCUS) enables fluid administration guided by fluid responsiveness, serving as one of the few non-invasive technological aids widely accessible both within and outside the intensive care unit. In this review, we focus on how POCUS can complement the evaluation of fluid responsiveness and fluid tolerance. The topics include a review of POCUS techniques to estimate the change in cardiac output following preload modifying manoeuvers, evaluation of thoracic fluid tolerance through lung ultrasound, and evaluation of systemic fluid tolerance through venous Doppler and the venous excess ultrasound (VExUS) assessment.