Cardiac Ultrasonography in the critical care setting- a practical approach to asses cardiac function
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Guy L.J. Vermeiren, Manu L.N.G. Malbrain, Jeroen M.J.B. WalpotAbstract/Text
Cardiac ultrasonography has become an indispensible tool in the management of hemodynamically unstable critically ill patients. Some consider it as the modern stethoscope. Echocardiography is non-invasive and safe while the modern portable devices allow to be used at the bedside in order to provide fast, specific and vital information regarding the hemodynamic status, as well as the function, structure and anatomy of the heart. In this review, we will give an overview of cardiac function in general followed by an assessment of left ventricular function using echocardiography with calculation of cardiac output, left ventricular ejection fraction (EF), fractional shortening, fractional area contraction, M mode EF, 2D planimetry and 3D volumetry. We will briefly discuss mitral annulus post systolic excursion (MAPSE), calculation of dP/dt, speckle tracking or eyeballing to estimate EF for the experienced user. In a following section, we will discuss how to assess cardiac preload and diastolic function in 4 simple steps. The first step is the assessment of systolic function. The next step assesses the left atrium. The third step evaluates the diastolic flow patterns and E/e’ ratio. The final step integrates the information of the previous steps. Echocardiography is also the perfect tool to evaluate right ventricular function with tricuspid annular plane systolic excursion (TAPSE), tissue Doppler imaging, together with inferior vena cava dimensions and systolic pulmonary artery pressure and right ventricular systolic pressure measurement. Finally, methods to assess fluid responsiveness with echocardiography are discussed with the inferior vena cava collapsibility index and the variation on left ventricle outflow tract peak velocity and velocity time integral. Cardiac ultrasonography is an indispensible tool for the critical care physician to assess cardiac preload, afterload and contractile function in hemodynamically unstable patients in order to fine-tune treatment with fluids, inotropes and/or vasopressors.