The Impact of Passive Leg Raising on Corrected Carotid Flow Time and Inferior Vena Cava Diameter Before and After Fasting: An Ultrasound‐Based Cross‐Sectional Study

Background and Aim Assessing the necessity for fluid resuscitation is critical in the emergency department, and sonography provides a less‐invasive, reproducible diagnostic modality for this purpose. This study aims to evaluate intravascular volume status in healthy individuals by analyzing alterations in corrected carotid flow time (FTc) and inferior vena cava (IVC) diameter via ultrasound before and after passive leg raising (PLR). Methods This prospective observational study was conducted with healthy individuals who underwent a 12‐h fasting protocol. Participants voluntarily fasted, and we measured variations in blood pressure, heart rate, FTc, and IVC diameter before and after PLR in both fasting and non‐fasting conditions. Results A total of 72 healthy male subjects were enrolled in the study. Statistically significant differences were observed in all measured parameters—blood pressure, heart rate, FTc, and IVC diameter—before and after PLR in both fasting and non‐fasting states ( p < 0.001). Furthermore, a significant inversely correlation was identified between the increase in FTc and the reduction in IVC collapsibility following PLR (fasting: p = −0.567, p < 0.001; non‐fasting: p = −0.301, p = 0.010). Conclusion FTc can be utilized as a reliable marker for assessing intravascular volume status, demonstrating a positive correlation with intravenous fluid administration. This index, when combined with other criteria for evaluating hemodynamic status, is effective for assessing patients' volume status.