Transthoracic Echocardiography for Monitoring Cardiopulmonary Interactions

Abstract

Critical care transthoracic echocardiography has become primary for the hemodynamic evaluation of patients with either shock or respiratory failure. This widely used technique permits assessment of cardiac function and can answer clinical questions in ICU patients in up to 80% of cases. Parasternal long and short axis views, apical 4- and 5-chamber views and subcostal windows are the primarily used views. Echocardiography has been demonstrated to provide not only accurate cardiac images but also hemodynamic evaluation. Pulmonary artery pressure, pulmonary artery occlusive pressure and cardiac output could be estimated using Doppler techniques with a good accuracy. By using transthoracic echocardiography in patients with shock, one can rule out pericardial tamponade and assess left and right ventricular function. Fluid-responsiveness can be predicted using inferior vena cava (IVC) and left ventricular size (LV). Usually patients are fluid-responders when IVC is very small (<13 mm) and/or left ventricle is small and hyperdynamic. Dynamic parameters such as the passive leg raising manoeuvre to predict the effect of fluid volume expansion on cardiac output can be reliably performed with echocardiography. Pitfalls and limits of transthoracic echocardiography need to be known by the users to avoid misinterpretations. Educational programs need to be further developed, and all intensivists should develop a basic level of understanding of it and should be included in the resident curriculum. At least one intensivist in each unit who is an expert on transthoracic echocardiography should be available.