Critical Care Echocardiography: A Primer for the Nephrologist

Abstract

Critical care echocardiography (CCE) refers to the goal-directed use of transthoracic or transesophageal echocardiography and represents one of the most common applications of critical care ultrasound. CCE can be performed at the point of care, is easily repeated following changes in clinical status, and does not expose the patient to ionizing radiation. Nephrologists who participate in the care of patients in the intensive care unit will regularly encounter CCE as part of the decision-making and bedside management of ICU patients. The four primary indications for CCE are the characterization of shock, evaluation of preload tolerance, evaluation of volume responsiveness, and serial hemodynamic assessment to evaluate response to therapeutic interventions. This article provides an overview of the anatomical structures that are routinely assessed in basic CCE, describes how these findings are incorporated into the clinical assessment of critically ill patients, and introduces some common applications of advanced CCE.

Keywords: Critical care; Echocardiography; Point of care ultrasound; Resuscitation; Shock.

Figure 1:

Reproduced with permission from Miller and Mandeville: The graphics demonstrate the pressure changes during the cardiac cycle with positive pressure ventilation. During inspiration, a rise in intrathoracic pressure is transmitted to the pericardium and increases transmural right ventricular pressure, resulting in dilation of the inferior vena cava and decreased superior vena cava diameter. Right ventricular stroke volume falls, while compression of the pulmonary vasculature forces blood into the left ventricle, increasing left ventricular stroke volume. After the pulmonary transition time, the left ventricle receives decreased blood and stroke volume falls. This effect is exaggerated in low circulating volume, and attenuated in volume overload or when either ventricle is failing..

Figure 2:

Selection of 2-dimensional echocardiographic still images depicting ideal and corresponding advanced measurement technique. 2a: End-Point Septal Separation – parasternal long transthoracic echocardiogram (TTE) view with corresponding M-mode imaging; 2b: Left Ventricular Outflow Tract Velocity Time Integral (LVOT VTI) – apical five chamber TTE view with pulsed wave Doppler imaging over the LVOT; 2c: Assessment of superior vena cava variation – transesophageal echocardiogram view with corresponding M-mode imaging; 2d: Mitral valve inflow Doppler – apical four chamber transthoracic echocardiogram (TTE) view with corresponding pulsed wave Doppler at the level of the mitral valve leaflet tips.