Role of End-Tidal CO2 During Passive Leg Raising to Predict Fluid Responsiveness in ICU

NCT07304648 | Not Yet Recruiting

• 1 other identifier: 2025-SAEK-0807
• Study Type: observational
• Target: 68
• Locations: 1 country
• Sites: 1

Brief Summary

This prospective observational study evaluates whether monitoring changes in exhaled carbon dioxide (End-Tidal CO2 or EtCO2) during a "Passive Leg Raising" (PLR) test can reliably predict fluid responsiveness in critically ill patients. In the Intensive Care Unit (ICU), fluid management is a critical balance; while fluid is necessary for tissue perfusion, overload can lead to severe complications. Traditional static measurements (like central venous pressure) are often unreliable for guiding therapy. Dynamic tests like PLR are preferred as they simulate a fluid bolus reversibly by shifting blood from the legs to the heart. Researchers will observe mechanically ventilated patients planned for fluid resuscitation. The study compares the accuracy of non-invasive EtCO2 changes during PLR against a reference standard "Mini Fluid Challenge" (100 mL fluid administration). Fluid responsiveness will be confirmed using echocardiographic measurements (LVOT-VTI) or arterial pressure changes. The goal is to validate EtCO2 as a practical, real-time tool for safe fluid management.

Conditions

Critical Illness; Circulatory Failure; Hypovolemia

Keywords

Fluid Responsiveness; Passive Leg Raising; End-Tidal CO2; Mini Fluid Challenge; Mechanical Ventilation; Intensive Care

Outcome Measures

Primary Outcomes (1)

• Change in End-Tidal Carbon Dioxide (Delta EtCO2) during Passive Leg Raising (PLR)

  The absolute difference in End-Tidal CO2 (EtCO2) levels will be calculated between the baseline measurement (T0, patient semi-recumbent at 45°) and the measurement taken during the Passive Leg Raising test (T1, patient supine with legs raised to 45°). The diagnostic accuracy of this Delta EtCO2 will be evaluated by comparing it against the patient's fluid responsiveness status (Responder vs. Non-Responder) determined by the subsequent Mini Fluid Challenge.

  Measured between 60 to 90 seconds after the position change.

Secondary Outcomes (6)

• Change in Arterial Blood Pressures (SAP, DAP, MAP)

  Measured between 60 to 90 seconds after the position change.

• Change in Heart Rate (Delta HR)

  Measured between 60 to 90 seconds after the position change.

• Change in Pulse Pressure Variation (Delta PPV)

  Measured between 60 to 90 seconds after the position change.

• Change in Oxygen Saturation (Delta SO2)

  Measured between 60 to 90 seconds after the position change.

• Change in Vena Cava Inferior (VCI) Distensibility Index

  Measured between 60 to 90 seconds after the position change.

Study Arms (2)

Fluid Responders

Patients who demonstrate a significant hemodynamic improvement following the Mini Fluid Challenge (MFC. Defined as an increase in Left Ventricular Outflow Tract Velocity Time Integral (LVOT-VTI) of \>10%. If VTI unavailable, increase in Systolic Arterial Pressure \> 4%, Pulse Pressure variation decrease \> 2%, or Mean Arterial Pressure increase \> 15%.

Fluid Non-Responders

Patients who do not demonstrate a significant hemodynamic improvement following the Mini Fluid Challenge (MFC). Defined as an increase in LVOT-VTI of \< 10% (or failure to meet the alternative blood pressure criteria).

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

The study population consists of adult patients (aged 18 years or older) admitted to the Intensive Care Unit (ICU) of a university hospital. Eligible participants are those who have been receiving mechanical ventilation support for at least 24 hours and have been identified by the primary intensive care team as requiring a fluid responsiveness assessment via a mini fluid challenge. The cohort includes patients with circulatory failure or suspected hypovolemia where fluid resuscitation is clinically indicated. Patients with contraindications to passive leg raising (e.g., intracranial hypertension, deep vein thrombosis), spontaneous breathing, or severe cardiac valve pathologies are excluded.

You may qualify if:

• Patients aged 18 years or older.
• Patients who have been followed in the intensive care unit (ICU) with mechanical ventilation support for at least 24 hours.
• Patients for whom a mini fluid challenge (MFC) is clinically planned by the intensive care team.
• Patients for whom informed consent has been obtained from first-degree relatives or a legal representative.

You may not qualify if:

• Patients younger than 18 years of age.
• Pregnant patients.
• Patients without consent from first-degree relatives or a legal representative.
• Patients with known deep vein thrombosis (DVT) in the leg veins (risk of embolism during leg raising).
• Patients with pathologies that may cause increased intracranial pressure (e.g., intracranial mass, hemorrhage).
• Patients with uncontrolled hypertension.
• Patients with severe cardiac disease (e.g., right heart failure, pulmonary hypertension, advanced valvular pathology).
• Patients with carbon dioxide (CO2) retention.
• Patients who have undergone hip surgery or hip replacement surgery where Passive Leg Raising (PLR) cannot be performed.
• Patients with spontaneous breathing.
• Patients with a probability of high intra-abdominal pressure.
• Patients who cannot lie in a supine position.
• Patients with current peripheral oxygen saturation (SpO2) \< 88%.
• Patients on mechanical ventilation requiring pressure support \> 16 mmHg or PEEP \> 10 mmHg.

Sponsors & Collaborators

• Izmir Katip Celebi University: lead

Study Sites (1)

Izmir Katip Celebi University Atatürk Training and Research Hospital

Izmir, Turkey (Türkiye)

Location

MeSH Terms

Conditions

Shock; Critical Illness; Hypovolemia

Condition Hierarchy (Ancestors)

Pathologic Processes; Pathological Conditions, Signs and Symptoms; Disease Attributes

Study Officials

• Murat Aksun, M.D.

  Izmir Katip Celebi University Atatürk Training and Research Hospital

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Murat Aksun, M.D.

CONTACT

+90 552 363 16 14; murataksun@yahoo.com

Ahmet Salih Tüzen, M.D.

CONTACT

+90 535 391 55 77; astuzen@icloud.com

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Target Duration: 1 Day
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Medical Doctor

Study Record Dates

• First Submitted: December 13, 2025
• First Posted: December 26, 2025
• Study Start: January 1, 2026
• Primary Completion (Estimated): January 1, 2027
• Study Completion (Estimated): July 1, 2027
• Last Updated: December 26, 2025

Record last verified: 2025-12

Locations

TU (1)