Ultrasound-Based Passive Leg Raising Test for Predicting Fluid Responsiveness Using Carotid Flow Velocity-Time Integral

The passive leg raising (PLR) test is a widely used noninvasive method to assess fluid responsiveness in critically ill patients. This study aimed to determine whether changes in carotid flow, assessed using echo-Doppler, could predict fluid responsiveness after a PLR. Conducted in two intensive care units in Argentina between February and April 2022, the study included patients with signs of tissue hypoperfusion who required fluid resuscitation. Patients were categorized as fluid responders if, after receiving a fluid bolus, their left ventricle outflow tract velocity-time integral (LVOT VTI) increased by more than 15%. The changes in carotid flow velocity-time integral (CF VTI) were assessed from the left supraclavicular region in a semi-recumbent position before and during the PLR. Among the 62 eligible patients, 50 (80.6%) were included in the analysis. The study found that the area under the receiver operating characteristic (ROC) curve for changes in CF VTI during the PLR was 0.869 (95% CI 0.743–0.947). A CF VTI increase of at least 11% during the PLR was found to predict fluid responsiveness with a sensitivity of 77.3% (95% CI 54.6–92.2%) and specificity of 78.6% (95% CI 59–91.7%). The positive predictive value was 73.9% (95% CI 57.4–85.6%) and the negative predictive value was 81.5% (95% CI 66.5–90.7%). The positive likelihood ratio was 3.61, while the negative likelihood ratio was 0.29. In conclusion, an increase greater than 11% in CF VTI during the PLR test could serve as a useful predictor for fluid responsiveness in critically ill patients, offering a noninvasive, ultrasound-based tool to guide clinical decisions.