Carotid Doppler Imaging as a Marker for Fluid Responsiveness

Background/Objective: Identifying fluid-responsive patients is essential in managing hemodynamic instability. Traditional static measures like central venous pressure (CVP) are often unreliable. Prior studies suggest that cardiac ultrasound (US), particularly carotid Doppler point-of-care ultrasound (POCUS), may correlate with pulmonary artery catheter (PAC)-derived cardiac output (CO), offering a noninvasive tool to assess fluid responsiveness. We aimed to evaluate the correlation between carotid ultrasound (US) parameters and pulmonary artery catheter (PAC) derived measurements in post cardiac surgery patients. Methods: We conducted a prospective cohort study on 50 postcardiac surgery patients from 2019 to 2022 in a single cardiothoracic ICU. Carotid US and PAC CO measurements were obtained at four intervals: pre- and post-passive leg raise (fluid challenge) on ICU admission, and one hour later. Fluid responsiveness was defined as a ≥10% increase in carotid blood flow, ≥7 ms increase in corrected flow time (FTc), or ≥10% change in respiratory peak carotid systolic velocity (ΔCDPV). Pearson's correlation and linear regression were used to assess associations between carotid US and PAC changes. Agreement in fluid responsiveness categorization (≥10% CO change) was evaluated using weighted Cohen's kappa. Significance was set at α = 0.05. Results: No significant correlation was found between changes in carotid US parameters and the PAC cardiac index (CI) at baseline or one hour for ΔCDPV, FTc, or carotid blood flow. A moderate correlation was observed between carotid blood flow and FTc at one hour (r = 0.41, p = 0.005). Regression and sensitivity analyses showed no significant associations. Conclusions: The carotid US parameters did not correlate with PAC-derived CO after passive leg raise. Further studies are needed to validate carotid POCUS in this setting.