Echocardiography Guided Fluid Resuscitation in Critically Ill Patients

Resuscitation often requires the infusion of intravenous fluid in an effort to reverse organ dysfunction. The harms of inappropriate use of fluid are becoming increasingly apparent The question of whether the patient improves with fluid, additional vasopressors or inotropes can be difficult to answer. The gold standard for assessing fluid responsiveness to guide fluid administration in critically ill patients is to perform a fluid challenge. The rationale for volume expansion is to increase the cardiac output (CO) and oxygen delivery to ultimately improve tissue oxygenation. This involves the infusion of a specific amount of intravenous fluid to assess ventricular preload reserve and subsequent systemic haemodynamic effects. In a patient with acute hemodynamic instability, a fluid challenge will cause an increase in stroke volume, according to the Frank-Starling curve. This increase in stroke volume has a salutary effect because it improves tissue perfusion. In contrast, higher hydrostatic pressures in the vascular system predispose the patient to edema, organic dysfunction, and increased risk of in-hospital mortality.

Fluid responsiveness is conventionally defined as an increase of at least 10% to 15% in SV in response to a fluid challenge, which is a reflection of the limits of precision of the technology used.

Assessment of the response in flow to a fluid challenge can be guided with echocardiography. It is achieved by measuring left ventricular outflow tract velocity time integral (LVOT VTI) immediately before and after fluid challenge.