Use of Ultrasonography to Determine Fluid-responsiveness for Shock in a Population of Intensive Care Unit Patients

Overview

The objective of our study is to determine the correlation of transthoracic ultrasonographic indices of fluid responsiveness to changes in direct measures of cardiac output and to compare them to other established predictors of fluid responsiveness such as central venous pressure variation, systolic arterial pressure variation and pulse pressure variation in a broad population of patients. Hypothesis: There will be a significant difference in the inferior vena cava respiratory variation and subclavian vein respiratory variation between responders and non-responders to intravenous fluid challenge in a broad population of patients with shock.

Shock is a common occurrence in the intensive care unit (ICU), and the management of this condition frequently requires the administration of intravenous fluids (IVF). Multiple studies have shown that only about 50% of these patients will respond to fluids. The ability to predict which patients will respond is an important tool for clinicians to treat shock while avoiding unnecessary fluid administration in those who are unlikely to respond. This is essential to avoid the adverse effects of fluid loading that can occur. A number of studies have attempted to determine predictors of volume-responsiveness through various methods, including the use of ultrasonography performed by intensivists, anesthesiologists and emergency medicine physicians. The currently published studies establish predictors of fluid-responsiveness in their populations. However, there has been large variability in the study designs, making it difficult to compare different modalities. The objective of our study is to determine the correlation of transthoracic ultrasonographic indices of fluid responsiveness to changes in direct measures of cardiac output and to compare them to other established predictors of fluid responsiveness such as central venous pressure variation, systolic arterial pressure variation and pulse pressure variation. Furthermore, we wish to include a broad range of patients with different types of shock in order to determine the generalized applicability of these indices. Additionally, reported success of intensivist-obtained echocardiographic images varies widely in the literature, but most studies do not report which views are most accessible. We plan to study prospectively which views are obtainable and correlate them to patient characteristics. This would potentially establish echocardiography by an intensivist as a widely applicable, non-invasive, and easily accessible method for determining fluid-responsiveness in a patient with shock. Achievement of this goal would allow clinicians to quickly identify those patients that would respond to fluids and at the same time minimize the administration of fluids to those in whom it is unlikely to benefit.