An observational study in Fluid Responsiveness, Acute Circulatory Failure and Shock, sponsored by Istanbul University - Cerrahpasa. Recruiting at 1 site in Turkey (Türkiye). Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-05-11.
Sponsored by Istanbul University - Cerrahpasa · Observational
This prospective single-center observational study aims to evaluate whether the ultrasound-measured femoral vein-to-femoral artery diameter ratio can predict fluid responsiveness in mechanically ventilated adult intensive care patients with acute circulatory failure or shock. Only patients who already have PiCCO monitoring as part of routine clinical care and for whom a fluid challenge is clinically indicated will be included. No additional invasive procedure will be performed for study purposes. Cardiac index will be measured with PiCCO before and after administration of 500 mL balanced crystalloid over 10 minutes, and femoral vein and femoral artery diameters will be measured by bedside ultrasonography. Fluid responsiveness will be defined as an increase of more than 10% in cardiac index after fluid administration. The study will assess the diagnostic performance of the femoral vein-to-femoral artery diameter ratio as a practical bedside parameter to support hemodynamic decision-making in critically ill patients.
Acute circulatory failure and shock are common conditions in the intensive care unit, and fluid administration remains a key component of hemodynamic management. However, unnecessary fluid loading may worsen tissue edema, oxygenation, and organ function. Therefore, practical bedside tools that help identify fluid-responsive patients are clinically important.
The aim of this study is to evaluate the clinical utility of the ultrasound-measured femoral vein-to-femoral artery diameter ratio in predicting fluid responsiveness in mechanically ventilated adult ICU patients with acute circulatory failure or shock. This is a prospective, single-center, observational study.
No additional invasive intervention will be performed for research purposes. PiCCO monitoring will not be initiated for study reasons; only patients who already have PiCCO monitoring as part of routine ICU management and who are scheduled to undergo a clinically indicated fluid challenge will be enrolled.
Before the fluid challenge, cardiac index will be recorded using PiCCO, and femoral vein and femoral artery diameters will be measured by bedside ultrasonography at the same anatomical level proximal to the femoral artery bifurcation. Each ultrasound measurement will be repeated at least three times, and the mean value will be recorded. A fluid challenge consisting of 500 mL balanced crystalloid administered over 10 minutes will then be performed according to routine clinical care. After the fluid challenge, cardiac index and the femoral vein-to-femoral artery diameter ratio will be reassessed using the same methods.
Fluid responsiveness will be defined as an increase of more than 10% in cardiac index after fluid administration. Responders and non-responders will be compared, and the diagnostic performance of the femoral vein-to-femoral artery diameter ratio will be analyzed.
Demographic data, baseline clinical findings, hemodynamic measurements, and ultrasound measurements will be collected and analyzed. Appropriate descriptive statistics, group comparisons, and diagnostic performance analyses will be used to evaluate the discriminative ability of the femoral vein-to-femoral artery diameter ratio. All data will be de-identified and handled in accordance with patient confidentiality principles.
487 studies on the registry are indexed under Shock; 107 are open to participants now.
This study's planned enrollment of 100 is close to the median of 100 across 247 observational studies indexed under Shock.
Browse Shock studies →Istanbul University - Cerrahpasa is the lead sponsor of 699 studies on the registry; 213 are open to participants now.
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The study population consists of adult intensive care unit patients with acute circulatory failure or shock who are receiving invasive mechanical ventilation and for whom the responsible intensive care physician has determined a clinical indication for a fluid challenge. Only patients who already have PiCCO monitoring in place as part of routine clinical care and in whom femoral vein and femoral artery ultrasonographic measurements can be obtained will be enrolled.
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You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bedside ultrasonographic measurement of femoral vein and femoral artery diameters at the same anatomical level proximal to the femoral artery bifurcation, with at least three repeated measurements and calculation of the femoral vein-to-femoral artery diameter ratio before and after a clinically indicated fluid challenge.
Diagnostic performance of the baseline femoral vein-to-femoral artery diameter ratio for predicting fluid responsiveness
Diagnostic performance of the baseline ultrasound-measured femoral vein-to-femoral artery diameter ratio in identifying fluid responders, assessed by receiver operating characteristic analysis (area under the curve). Fluid responsiveness will be defined as an increase of more than 10% in cardiac index after administration of 500 mL balanced crystalloid over 10 minutes.
Time frame: Baseline assessment before fluid challenge, with responder status determined 10 minutes after completion of the fluid challenge
Percent change in cardiac index after fluid challenge
Percent change in PiCCO-derived cardiac index after administration of 500 mL balanced crystalloid over 10 minutes.
Time frame: Before fluid challenge and 10 minutes after completion of the fluid challenge
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