Noninvasive cardiac output measurement in cardiovascular ICU-patients – comparison of conventional impedance cardiography, electrical velocimetry and thermodilution methods

Objective: Especially in cardiosurgical patients (pts) with impaired cardiac function, hemodynamic monitoring is essential. Impedance cardiography (ICG) is a non-invasive, accurate and cost-effective method for continous measuring of cardiac output (CO). Electrical Velocimetry (EV) is a new approach using the „Bernstein-Osypka“-Equation for CO-estimation. We therefore studied the ability of two ICG methods to estimate correct CO in comparing the measurements with conventional invasive PICCO-and pulmonary artery catheter (PAK) data.

Methods: In 32 postoperative ICU pts (age 74.7±14.6yrs) with invasive hemodynamic monitoring, CO was measured using PICCO (Grp A, 19 pts) or PAK (Group B, 13 pts). Simultaniously, non-invasive BZ (BioZ.com, GE Medical monitor) – and EV (AESCULON, Osypka Medical monitor) CO-estimation was recorded.

Results: A significant correlation was found between invasive and non-invasive CO-measurements in both groups, e.g. Grp A: BZ (r=0.86, p<0.001); Group B: AE (r=0.88, p<0.002). Bland-Altman analysis revealed almost equal accuracy in Group A (BZ: bias –1.32l/min±1.29; EV: bias –0.95l/min±1.32) while in Group B EV produced slightly better results (BZ: bias –0.81l/min±1.54; EV: bias –0.74l/min±0.86).

Conclusions: Our results demonstrate that ICG provides clinically acceptable determination of hemodynamic parameters in cardiosurgical ICU patients. EZ CO-evaluation was slightly more accurate especially compared to PAK measurement. Nevertheless limitations of the new method have to be investigated in further studies before routine usage of EV on the ICU or stepdown.