The endothelium is the inner layer of blood vessels, serving as a physical barrier and playing a metabolic role in the organisms homeostasis. Considering that cardiovascular diseases remain among the leading causes of global morbidity and mortality, identifying conditions like endothelial dysfunction, which span various pathologies, is significant. This dysfunction has been extensively described in cardiovascular pathologies, recognized as a risk factor for the development of long-term complications, and playing a crucial role in the atherosclerotic process, even preceding it during thickening, plaque formation, and subsequently in the pathophysiology of inflammation, plaque vulnerability, and eventual rupture. Various animal studies have demonstrated impaired endothelial function is associated with poorer cardiovascular performance. Despite this, evaluating this organ is not routine in clinical practice, and even less so in the perioperative context, as many techniques require sampling of endothelial tissue, consequently causing injury to the vascular tree. Several non-invasive techniques have been developed to evaluate endothelial function, which have been associated with the presence of atherosclerosis or as predictors of cardiovascular events. One such technique used in functional studies is the Flow-Mediated Dilation (FMD) test. This test is based on the normal vasodilation reactive to ischemia caused by the release of endothelial nitric oxide due to increased turbulence over the endothelium. Initially used in endothelial function research laboratories, it has gradually been adopted in clinical practice with an increasing number of publications. This article describes the theoretical foundations supporting the phenomenon and provides a guide to adapting its use in daily surgical settings.