Aim: Predicting fluid responsiveness in patients with shock is critical. This study aimed to evaluate the diagnostic accuracy of dynamic ultrasound-derived indices in predicting fluid responsiveness, using bioreactance-based cardiac output monitoring as the reference standard.
Study Design: A total of 39 adult patients diagnosed with shock who were receiving mechanical ventilation were included. Hemodynamic parameters were assessed using ultrasound [left ventricular outflow velocity-time integral (LVOT-VTI), respirophasic variability of LVOT-VTI, corrected carotid flow time (cCFT), respirophasic variability of carotid artery peak flow velocity (∆Vpeak), and the inferior vena cava distensibility index (dIVC)] and pulse pressure variation (PPV) via invasive arterial monitoring. The bioreactance-derived stroke volume index change after passive leg elevation (ΔSVI ≥10%) served as the reference standard for fluid responsiveness.
Results: Fluid responsiveness was present in 53.8% of patients according to ΔSVI. LVOT-VTI variability (area under the curve [AUC] 0.847, 95% confidence interval [CI]: 0.726–0.968, sensitivity 85.0%, specificity 66.6%) and PPV (AUC 0.832, 95% CI: 0.679–0.985, sensitivity 94.4%, specificity 70.5%) demonstrated the highest predictive accuracy. Carotid flow variability showed moderate performance (AUC 0.754), while dIVC yielded the lowest diagnostic accuracy (AUC 0.676). A strong correlation was observed between bioreactance-derived cardiac index and LVOT-VTI (r=0.835, p<0.001), whereas cCFT was not significantly correlated.
Conclusions: Left ventricular outflow velocity-time integral variability demonstrated strong diagnostic accuracy in predicting fluid responsiveness in mechanically ventilated patients with shock when confirmed using bioreactance monitoring. IVC distensibility and carotid flow variability showed limited reliability.