Echocardiography, Thoracic Fluid Content and Lung Ultrasound Monitoring as Predictors of Pulmonary Edema in Severe Preeclampsia

Outside pregnancy, transthoracic cardiac ultrasound (echocardiography) and lung ultrasound have become important diagnostic and monitoring tools in critically ill patients. Echocardiography allows a rapid and non-invasive assessment of myocardial contractility and preload, and lung ultrasound can be used to determine the amount of extravascular lung water (EVLW).

In pregnancy, there is evidence of a good correlation between non-invasive hemodynamic monitoring by echocardiography and invasive monitoring using a pulmonary artery catheter. Previous studies have shown that invasive hemodynamic monitoring could facilitate fluid management in patients with PE. However, recent studies have examined the utility of echocardiography in combination with lung ultrasound for guiding fluid therapy in patients with severe PE.

Thoracic fluid content (TFC) is one of the many variables measured by the ICON electrical cardiometry (EC) device (Osypka Medical, etc.). The ICON device is one relatively new proprietary implementation of impedance cardiography technology, which is also often called "thoracic electrical bio-impedance". Impedance cardiography is based on measuring the changes in total resistance of the thorax to electric current. The impedance (Zo) to electric current is determined by the resistance of different tissues such as bone, muscles, and fluids. The fluid compartment is considered the dynamic component that will cause short term changes in thoracic impedance. TFC is calculated as the reciprocal of the total thoracic impedance (1/ Zo) and is considered a numerical measure of total (intravascular and extravascular) thoracic fluid. Although TFC is a measure of both extra and intra-vascular thoracic fluid, the investigators hypothesized that it might provide an estimate of the increase in intrathoracic fluids such as to facilitate the risk of pulmonary edema.