Assessment of Carotid Doppler Parameters to Evaluate Volume Status: A Prospective Observational Study

Accurate assessment of volume status and fluid responsiveness is essential to guide fluid therapy, as unnecessary fluid administration may lead to fluid overload and adverse outcomes. Carotid Doppler ultrasound has emerged as a rapid, noninvasive alternative to more technically demanding echocardiographic measures. This study evaluated the utility of carotid Doppler-derived corrected flow time (FTc) and velocity-time integral (VTI), and their changes after passive leg raise (PLR), in assessing volume status and preload responsiveness.

We conducted a prospective observational study during Ramadan at a tertiary academic medical center. A total of 202 participants were enrolled, including 103 fasting individuals assessed during presumed relative dehydration and after rehydration, and 99 nonfasting hydrated controls. Carotid Doppler measurements of FTc, VTI, and V_max were obtained before and after PLR. Diagnostic performance of percent changes in FTc (ΔFTc) and VTI (ΔVTI) was evaluated using receiver operating characteristic analysis.

Participants in the fasting group underwent a mean fasting duration of 12.4 ± 1.1 hours and consumed a mean of 920 ± 352 mL of fluid after breaking the fast. PLR induced significantly greater increases in FTc and VTI during presumed relative dehydration. A ≥10% increase in VTI was observed in 57.2% of presumed relative dehydrated participants compared with 26.3% of hydrated controls and 20.4% of rehydrated participants. Similarly, a ≥5% increase in FTc was observed in 47.6%, 17.2%, and 22.3% of participants, respectively. Receiver operating characteristic analysis demonstrated moderate discriminatory performance for presumed relative dehydration, with areas under the curve of 0.708 for ΔVTI and 0.715 for ΔFTc. Optimal cutoff values were 5.92% for ΔVTI and 5.05% for ΔFTc.

Carotid Doppler-derived FTc and VTI are promising noninvasive markers of volume status and preload responsiveness. ΔVTI demonstrated greater sensitivity, whereas ΔFTc provided higher specificity, supporting the potential role of carotid Doppler ultrasound as a practical bedside tool for hemodynamic assessment.