Assessment of method agreement between two minimally invasive hemodynamic measurements in septic shock patients on high doses of vasopressor drugs. A preliminary study.

Background: Minimally invasive hemodynamic monitoring is still controversial among the methods used to assess the hemodynamic profile of the septic shock patient. The aim of this study was to test the level of agreement between two different devices.

Methods: We collected 385 data entries during 12-hour intervals from four critically ill patients with septic shock and high doses of vasoactive therapy using two minimally invasive methods at the same time: Vigileo™ device which uses the pulse contour principle, and EV1000™ monitoring platform which uses the transpulmonary thermodilution principle. The studied parameters were Stroke Volume (SV), Cardiac Output (CO) and Mean Arterial Pressure (MAP). We tested the agreement by performing the visual examination of data patterns using graphs and studying the bias, limits of agreement and creating Bland-Altman plots. For assessing the systematic, proportional and random differences, we computed a Passing-Bablock regression with the CUSUM test for linearity.

Results: The one sample t-Test for the differences between the two methods against the null value was statistically significant for the studied parameters (p < 0.0001). The Bland-Altman analysis found no agreement between the data obtained using the two techniques, with calculated error percent as high as 88.28% for SV, 82.02% for CO and 42.06% for MAP. The Passing-Bablock regression analysis tested positive for systematic differences, but this could not be accounted for.

Conclusion: We found no agreement between data obtained from the studied devices; therefore, these cannot be used interchangeably for critically ill septic shock patients on high doses of vasoactive substances.