Comparison between an uncalibrated pulse contour method and thermodilution technique for cardiac output estimation in septic patients.

Background: The purpose of this study was to evaluate the reliability of a new uncalibrated pulse contour method, the MostCare, in determining cardiac output (CO) in septic patients.

Methods: Thirty patients with septic shock admitted to an intensive care unit, receiving a norepinephrine infusion and requiring haemodynamic monitoring with a pulmonary artery catheter, were prospectively enrolled. Thermodilution measurements of CO (ThD-CO) were considered as the 'gold standard'. MostCare was connected to the monitoring system of the radial arterial pressure waveform to obtain a continuous CO calculation (MostCare-CO). ThD-CO and MostCare-CO measurements were recorded at three different haemodynamic states: baseline (T1), after raising mean arterial pressure (MAP) to 90 mm Hg by increasing the norepinephrine infusion (T2), and after returning the MAP to baseline value by decreasing vasopressor therapy (T3). A Bland-Altman and linear regression analyses were performed.

Results: A total of 90 paired ThD-CO and MostCare-CO measures were obtained (range 4.1-13.9 litre min(-1) for ThD-CO and 4.5-13.5 litre min(-1) for MostCare-CO). A good correlation between ThD-CO and MostCare-CO was observed (R = 0.93). The mean bias between the two techniques was -0.26 litre min(-1) (sd 0.98 litre min(-1)) and the 95% limits of agreement were -2.22 to 1.70 litre min(-1). The percentage of error was 25%. Pearson's R was 0.94, 0.92, and 0.93 at T1, T2, and T3, respectively.

Conclusions: MostCare-CO and ThD-CO showed a good agreement at each time of the study. The reliability of the MostCare system was not affected by the vascular tone changes produced by a norepinephrine infusion.