Femoral vein-to-artery diameter ratio to predict fluid responsiveness

Prediction of Fluid Responsiveness Using the Femoral Vein-to-Artery Diameter Ratio: A Prospective Observational Study

This project will test whether a bedside ultrasound measurement of the femoral vein-to-artery diameter ratio can tell if mechanically ventilated ICU patients with acute circulatory failure or shock will increase their cardiac output after a 500 mL fluid bolus.

Quick facts

• Study type: Observational
• Enrollment: 100 (estimated)
• Ages: 18 Years and up
• Sex: All
• Sponsor: Istanbul University - Cerrahpasa (Academic / other)
• Locations: 1 site (Istanbul, Istanbul)
• Trial ID: NCT07546656 on ClinicalTrials.gov

What this trial studies

This is a prospective, single-center observational study enrolling mechanically ventilated adult ICU patients with acute circulatory failure or shock who already have PiCCO monitoring and a clinician-planned fluid challenge. Baseline cardiac index will be recorded with PiCCO and femoral vein and artery diameters measured by bedside ultrasound, with each ultrasound repeated at least three times and averaged. A 500 mL balanced crystalloid will be given over 10 minutes and cardiac index remeasured, with fluid responsiveness defined as a >10% increase in cardiac index. The diagnostic performance of the femoral vein-to-artery diameter ratio will be compared to the PiCCO-derived change in cardiac index, and no additional invasive procedures will be performed for research purposes.

Who should consider this trial

Good fit: Adults in the study ICU on invasive mechanical ventilation with acute circulatory failure or shock who already have PiCCO monitoring and a planned clinical fluid challenge are the ideal candidates.

Not a fit: Patients who are not mechanically ventilated, lack PiCCO monitoring, have contraindications to femoral ultrasound (for example groin injury) or cannot undergo a fluid challenge are unlikely to benefit from these results.

Why it matters

Potential benefit: If successful, this simple ultrasound ratio could provide a quick bedside tool to help clinicians choose who will benefit from fluids and avoid unnecessary fluid loading.

How similar studies have performed: Other ultrasound-based markers such as IVC or venous size indices have shown mixed accuracy, and the femoral vein-to-artery ratio is a relatively novel bedside parameter with limited prior validation.

Eligibility criteria

Inclusion Criteria:

* Adult patients aged 18 years or older
* Admission to the intensive care unit where the study is being conducted
* Receiving invasive mechanical ventilation
* Clinical indication for a fluid challenge due to acute circulatory failure or shock, as determined by the responsible intensive care physician
* PiCCO monitoring already in place as part of routine clinical care
* Clinical conditions allowing collection of pre- and post-fluid challenge cardiac index and ultrasonographic measurements
* Technical feasibility of femoral vein and femoral artery diameter measurements by ultrasonography

Exclusion Criteria:

* Age younger than 18 years
* Failure to obtain written informed consent from the patient or legally authorized representative before enrollment
* Absence of PiCCO monitoring as part of routine clinical care or no clinical plan for fluid challenge
* Inability to complete pre- and post-fluid challenge measurements (e.g., early death, urgent surgery, transfer)
* Local conditions preventing reliable femoral ultrasonographic assessment, including open wound, infection, dressing, major anatomic obstacle, poor image quality, known femoral vein thrombosis, or severe vascular pathology on the relevant side
* Conditions likely to significantly impair the reliability of thermodilution measurements (e.g., severe tricuspid regurgitation or significant intracardiac shunt)
* Major treatment changes during the fluid challenge that preclude comparable measurements (e.g., major vasopressor dose change, major ventilator setting change, new arrhythmia)
* Missing or inadequate data judged by the investigators to compromise data integrity, including absence of measurements required for the primary outcome

Where this trial is running

Istanbul, Istanbul

• Istanbul University Cerrahpasa Medical Faculty — Istanbul, Istanbul, Turkey (Türkiye) (Recruiting)

Study contacts

• Study coordinator: mert katılmış

Conditions Fluid Responsiveness; Acute Circulatory Failure; Shock; Hemodynamic Monitoring; Ultrasonography; Femoral Vein; Femoral Artery; PiCCO