Comparison of continuous cardiac output monitoring derived from regional impedance cardiography with continuous thermodilution technique in cardiac surgical patients

Background: Cardiac output (CO) assessment is a corner stone in advanced haemodynamic management, especially in critical ill patients. The present study was conducted to validate cardiac index and cardiac output by NICaS (TM) with the thermodilution technique using pulmonary artery catheter in post-operative cardiac surgical patients. Materials and Methods: This was a prospective observational clinical study conducted at a tertiary care hospital. 23 adult patients in the age range of 18-65 years who had undergone for elective coronary artery bypass grafting were included in the study. Results: Spearman's correlation coefficient of cardiac index between continuous Thermodilution (cTD) and Non-Invasive Cardiac System (NICaS (TM)) showed a good correlation (r = 0.765, 95% confidence interval 0.70 to 0.82, P < 0.0001). There was a good correlation between cTD and NICaS (TM) for cardiac output (r = 0.759, 95% confidence interval 0.69 to 0.81, P < 0.0001), Bland-Altman plot for cardiac index between cTD and NICaS (TM) showed a mean bias of -0.66 +/- 0.6919 with limits of agreement being -2.02 to 0.6936. Bland-Altman plot for cardiac output between cTD and NICaS (TM) showed a mean bias of -1.0386 +/- 1.17 with limits of agreement being -3.34 to + 1.26. Percentage error for cardiac index and cardiac output were 64.78% and 64% respectively. Polar plot analysis showed an angular bias of 6.32 degrees with radial limits of agreement being -8.114 degrees to 20.75 degrees for cardiac index and angular bias of 5.6682 degrees with radial limits of agreement being -9.1422 degrees to 20.4784 degrees for cardiac output. Conclusion: NICaS (TM) demonstrated a good trending ability for both CI and CO. However, NICaS (TM) derived parameters are not interchangeable with the values derived from continuous thermodilution technique.