Comparison of Hemodynamic Variables Associated with Cardiac Output in Patients in the Intensive Care Unit

ABSTRACT

PURPOSE: Dynamic parameters, including end-tidal carbon dioxide (ETCO₂), peak velocity variation in the common carotid artery (pvvCCA), distensibility index of the internal jugular vein (dIJV), and distensibility index of the inferior vena cava (dIVC) have been used to predict fluid responsiveness in fully sedated patients under positive mechanical ventilation. We aimed to compare the cardiac output (CO) with all these dynamic parameters upon changing positions. METHODS: This prospective cohort study compared the changes in all parameters that alter CO after changing positions, including upper body at 60°and 30°, supine position, and lower body at 30°and 60°, as measured using ultrasonography, between June 2015 and September 2016. RESULTS: CO was correlated with parameters, including dIJV, pvvCCA, and ETCO₂, in positively ventilated patients with nonspontaneous breathing (p=0.001, p=0.014, and p=0.006, respectively). Among these parameters, ETCO₂ showed to have the best correlation with CO change after position change (coefficient 0.412). Correlations of CO with central venous pressure, blood pressure, and dIVC were not statistically significant. The mean value of CO in elevated lower body positions was slightly lower than the mean value of CO in supine position (5.231 vs. 5.752 L/min, p=0.516). CONCLUSION: Measuring the changes of ETCO₂ in patients with positive mechanical ventilation might allow the most accurate prediction of CO changes. The position change from elevated upper body to supine position could better induce CO changes than that performed similarly with passive leg raising.