Non-invasive continuous arterial pressure and cardiac index monitoring with Nexfin after cardiac surgery

This observational study was designed to evaluate the reliability and precision of a new digital photoplethysmographic device (Nexfin, BMEYE B.V., Amsterdam, The Netherlands) for continuous and non-invasive assessment of arterial pressure and cardiac output. Fifty consecutive adult subjects were prospectively enrolled at admission to the intensive care unit after conventional cardiac surgery and investigated hourly from T0 to T4. Simultaneous comparative systolic, diastolic, and mean arterial pressures and cardiac index (CI) data points were collected from an invasive radial artery catheter, transpulmonary thermodilution catheter, and the Nexfin device. Correlations were determined by linear regression. The BlandAltman analysis was used to compare bias, precision, and limits of agreement. Six (12) subjects were excluded from the analysis because of the inability to obtain a reliable photoplethysmographic signal. No complications were observed. A significant relationship was found between absolute values of photoplethysmographic and radial systolic (r(2)0.56, P0.001), diastolic (r(2)0.61, P0.001), and mean (r(2)0.77, P0.001) arterial pressures. A significant relationship was also found between transpulmonary thermodilution and Nexfin CI absolute values (r(2)0.33, P0.001). Bias, precision, and limits of agreement between the mean photoplethysmographic and radial arterial pressures were 4.6 (95 confidence interval: 3.75.5), 6.5, and 17.3 to 8.1 mm Hg, respectively. The percentage error between transpulmonary thermodilution and the Nexfin for CI measurement was 50. The Nexfin device is safe, convenient, and reliable in measuring continuous non-invasive arterial pressure but not interchangeable with transpulmonary thermodilution to monitor CI.