Assessment of an uncalibrated pressure waveform device's ability to track cardiac output changes due to norepinephrine dose adjustments in patients with septic shock: a comparison with Doppler echocardiography.

OBJECTIVES

The FloTrac Vigileo (FTV) estimates cardiac output (CO) on the basis of an uncalibrated arterial pressure waveform. To assess the ability of the third-generation of FTV (v.3.02) to track changes in CO following norepinephrine dose adjustment in patients with septic shock, we performed a comparative study using Doppler echocardiography (DE).

STUDY DESIGN

Prospective observational study.

PATIENTS

We prospectively included 20 mechanically ventilated patients receiving norepinephrine and monitored with the FTV. Five minutes after each change in norepinephrine dose (decided by the attending physician), CO was measured simultaneously with the FTV (CO(FTV)) and DE (CO(DE)). The changes in CO were compared. ROC curves were built to assess the ability of FTV to detect significant changes in CO(DE) of at least 15%.

RESULTS

Ninety pairs of CO variations measurements were made. The intertechnique correlation coefficient for changes in CO of at least 15% was r=0.59; P=0.0009. The AUC of a ROC curve built to test the FTV's ability to detect a CO(DE) increase of 15% or more was 0.783 (±0.083) (P=0.005). A CO(FTV) threshold value of 15% had a sensitivity of 54% (25-81) and a specificity of 87% (77-94). For a CO(DE) decrease of 15% or more, the ROC curve had an AUC of 0.616 (±0.075) (P=0.12) and a CO(FTV) threshold value of 13% yielded a sensitivity of 53% (27-79) and a specificity of 72% (60-82).

CONCLUSIONS

The FTV was unable to accurately track changes in CO following norepinephrine dose adjustments in critically ill patients with septic shock.