Comparison of electrical velocimetry and transthoracic thermodilution technique for cardiac output assessment in critically ill patients

BACKGROUND AND OBJECTIVE: The results of studies validating the assessment of cardiac output by pulmonary artery thermodilution and a modified algorithm using thoracic bioimpedance/electrical velocimetry in patients undergoing elective cardiac surgery are conflicting. The present observational study was designed to detect whether electrical velocimetry measurements are comparable to transthoracic thermodilution in septic patients after major general surgery. METHODS: Cardiac output was assessed simultaneously by thoracic bioimpedance measurement/electrical velocimetry and transthoracic thermodilution technique (PiCCO) in 30 patients with severe systemic inflammatory response syndrome or sepsis with haemodynamic instability being treated in the surgical intensive care unit of an university hospital. RESULTS: Thirty simultaneous measurements were taken with both methods. The Bland-Altman analysis of agreement revealed a bias of -0.3 l min(-1) with a precision of +/-1.9 l min(-1) and wide limits of agreement (-4.1-3.5 l min(-1)). The percentage error was 54%. CONCLUSION: There was poor agreement between the values of cardiac output estimation by transthoracic thermodilution and those by electrical velocimetry. Electrical velocimetry could not replace invasive monitoring in this trial.