Cardiac output measurement: Lack of agreement between thermodilution and thoracic electric bioimpedance in two clinical settings

Abstract

Study objective: To determine the agreement between thermodilution (TD) and thoracic electric bioimpedance (TEB) techniques in cardiac output (CO) measurements in hyperdynamic kidney recipients and normodynamic patients subjected to radical cystectomy. The main objective was to determine the reliability of TEB in CO measurement. Design: Open two-group study. Setting: Unïversity hospital. Patients: 19 kidney recipients and 5 radical cystectomy patients. Interventions: Radial artery cannula and pulmonary artery floating catheter were inserted. The eight ECG spot electrodes of the TEB device were situated on the body surface. Measurements and Main Results: Simultaneous CO measurements with TD and TEB were recorded at strategic points during the dynamic state of anesthesia and surgery. The mean difference (bias, TD-TEB) was higher in KRs (1.36 L/min) than radical cystectomy patients (− 0.69 L/min). The corresponding 95% confidences of the bias were 1.10 to 1.54 L/min and −0.83 to −0.55 L/min. The precisions (SDs of bias) in kidney recipients and radical cystectomy patients were 1.08 L/min and 0.66 L/min, respectively. The limits of agreement were −0.97 to 3.51 L/min in kidney recipients and −1.99 to 0.61 L/min in radical cystectomy patients. The 95% confidences of the limits of agreement in kidney recipients were −1.09 to −0.49 for the lower limit and 3.21 to 3.81 for the upper limit. The corresponding values in radical cystectomy patients were −2.23 to −1.75 L/min and 0.37 to 0.85 L/min. Conclusions: These findings demonstrate lack of agreement between TEB and TD in CO measurements in a hyperdynamic and a normodynamic clinical setting. It is concluded that the TEB device is unreliable in CO measurement and cannot replace or be interchanged with TD.