Association of Respiratory Variation of Superior Vena Cava in Transthoracic View and Fluid Responsiveness in Critically Ill Patients

Prospective evaluation of diameter variability of the superior vena cava by transthoracic echocardiography as fluid responsiveness predictor in critically ill patients:

Background Fluid administration is frequent in critically ill patients, particularly during reanimation and its empirical use is recommended as an initial step during this phase.

However, even though excess fluid administration is associated to negative outcomes fluid use is still being empirical and with scarce application of responsiveness predictors before its indication.

Different measurements or maneuvers exist, that allow clinicians to predict if a patient would present a positive fluid response, usually defined as cardiac output increasing 15% when infusing 500ml of crystalloids, and application of these predictive parameters could have clinical benefits on outcomes by avoiding inappropriate fluid administration.

As for the variables used, different types stand out. In general, flow or pressure variations originated in cardiothoracic interaction, auto-infusion and reduced fluid test evaluations such as the "mini" o "micro" fluid tests, in addition venous diameter variations in ultrasound evaluation with variable accuracy depending on the context. However, cardiothoracic interaction variables might have false positive results when right ventricular failure is present, given the cyclic increment on its afterload induced by positive pressure ventilation, reducing right ventricle stroke volume limiting its application in established or unknown and probable right heart failure if and advanced hemodynamic monitoring has not been performed to rule it out.