Third-generation FloTrac/Vigileo does not reliably track changes in cardiac output induced by norepinephrine in critically ill patients

The ability of the third-generation FloTrac/Vigileo software to track changes in cardiac index (CI) induced by volume expansion and norepinephrine in critically ill patients is unknown. In subjects with circulatory failure, we administered volume expansion (20 subjects) and increased (20 subjects) or decreased (20 subjects) the dose of norepinephrine. We measured arterial pressure waveform-derived CI provided by the third-generation FloTrac/Vigileo device (CIpw) and transpulmonary thermodilution CI (CItd) before and after therapeutic interventions. Considering the pairs of measurements performed before and after all therapeutic interventions (n60), a bias between the absolute values of CIpw and CItd was 0.26 (0.94) litre min(1) m(2) and the percentage error was 54. Changes in CIpw tracked changes in CItd induced by volume expansion with moderate accuracy [n20, bias0.11 (0.54) litre min(1) m(2), r(2)0.26, P0.02]. When changes in CItd were induced by norepinephrine (n40), a bias between CIpw and CItd was 0.01 (0.41) litre min(1) m(2) (r(2)0.11, P0.04). The concordance rates between changes in CIpw and CItd induced by volume expansion and norepinephrine were 73 and 60, respectively. The bias between changes in CIpw and CItd significantly correlated with changes in total systemic vascular resistance (r(2)0.41, P0.0001). The third-generation FloTrac/Vigileo device was moderately reliable for tracking changes in CI induced by volume expansion and poorly reliable for tracking changes in CI induced by norepinephrine.