PICCO versus electrical cardiometry, 2D and 3D transthoracic echocardiography for hemodynamic monitoring in ICU patients

Hemodynamic monitoring with measurement of cardiac output (CO) is essential for understanding shock pathophysiology and thus enabling optimal care for patients in the ICU. There are various methods for monitoring CO, which differ in degree of invasiveness. The aim of our study was to determine CO using 2D echocardiography, 3D echocardiography as well as electrical cardiometry (ICON®, OSYPKA MEDICAL, Berlin, Germany) and to compare these non-invasive methods to the clinically established but invasive transpulmonary thermodilution technique (PICCO®, Getinge, Gothenburg, Sweden) as a reference method. 

METHODS

We undertook 11 CO measurements in 8 critically ill patients treated in our ICU. Initially, continuous measurement of CO was established using electrical cardiometry, a non-invasive procedure in which electrodes placed on the skin measure changes in thoracic impedance, which is used to calculate CO with the help of filtering techniques. This was followed by a detailed 2D echocardiography with determination of the LVOT diameter and PW flow in the LVOT. Subsequently, 3D echocardiographic data sets were recorded. From these, CO was calculated in two different ways: firstly, using post-procedural 3D planimetry of the LVOT and calculating the CO by measuring the PW flow in the LVOT. 3D planimetry of the LVOT was performed in both the parasternal long axis (PLAX) and apical 5-chamber view (5-CHV). Secondly, the CO was determined directly from the 3D data set using Dynamic HeartModel^A.I. (DHM, Philips Healthcare, Amsterdam, Netherlands) which utilizes speckle tracking technology. Then, a measurement of CO was carried out using the PICCO® system. Measurements were compared using Pearson’s correlation coefficient and the Bland-Altman method.

RESULTS

Compared to the reference method (PICCO®), all echocardiographic methods showed a significant correlation with regard to CO (see table 1) with correlation coefficients ranging from 0,43 (DHM) to 0,64 (3D PLAX). Mean bias for echocardiographic methods ranged from 0,44l/min (2D TTE) to 0,56l/min (3D TTE PLAX). All but one 2D TTE measurements fell within the predefined ranged of mean± 1,96xSD for maximal allowed difference in the Bland-Altman model (see figure 1). Electrical cardiometry did not show significant correlation with PICCO and mean bias was 0,44 (table 1/figure 1).

CONCLUSIONS

Our results show a significant correlation between measuring CO using transpulmonary thermodilution and all other tested methods except for electrical cardiometry. The method demonstrating the strongest correlations to PICCO® was 3D echocardiographic planimetry of the LVOT in the PLAX.

Table 1: Correlation and mean bias of CO measurements using transpulmonary thermodilution compared to other methods