The Value of Partial Arterial Carbon Dioxide Pressure - End-Tidal Carbon Dioxide Gradient Courses in Predicting Acute Renal Injury in Critically Ill Patients on Mechanical Ventilation: A Novel Hemodynamic Marker?

End-tidal carbon dioxide (EtCO₂) refers to the level of carbon dioxide in the air exhaled during expiration and is measured using capnography. EtCO₂ is an important monitoring parameter in the management of critically ill patients on mechanical ventilation, providing indirect information about the patient's cardiac output, pulmonary perfusion-ventilation (V/Q) status, and metabolic activity. The Pa-EtCO₂ gradient, the difference between EtCO₂ and arterial CO₂ partial pressure (PaCO₂), changes significantly, especially in cases of hemodynamic deterioration, microcirculatory failure, and increased dead space. Therefore, the gradient is considered a potential indicator of perfusion in critically ill patients. In critically ill patients on mechanical ventilation, the usability of changes (courses) of the Pa-EtCO₂ gradient over time is being evaluated not only as an indicator of ventilation but also as a dynamic and indirect predictor of hemodynamic status and renal perfusion. Therefore, it should be investigated whether the Pa-EtCO2 gradient is a suitable parameter for early detection of AKI (acute kidney injury) development in patients with renal perfusion impairment.

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Key information

Conditions

Acute Kidney Injury Female Urogenital Diseases Female Urogenital Diseases and Pregnancy Complications Kidney Diseases Male Urogenital Diseases Renal Insufficiency Urogenital Diseases Urologic Diseases Ventilated Patient in Intensive Care

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Malatya Training and Research Hospital

Malatya, Osmaniye, +90(505)620-3888, Turkey (Türkiye)

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Patients over 18 years of age
patients under mechanical ventilation
initiation of EtCO₂ monitoring within the first hour of admission to the ICU
patients monitored in the ICU for at least 24 hours
having undergone arterial blood gas analysis (for PaCO₂ measurement) within the first 24 hours.

Exclusion criteria

Patients under 18 years of age
intensive care unit monitoring shorter than 24 hours
missing or inaccessible clinical data
chronic renal failure
acute renal failure present at admission to intensive care unit
advanced pulmonary diseases affecting EtCO₂ measurement (e.g., severe obstruction, giant bulla, advanced emphysema)
patients in whom PaCO₂ measurement cannot be performed

Treatment and study plan

Primary outcomes

Change From Baseline in PaCO₂-EtCO₂ Gradient at 6, 12, and 24 Hours After ICU Admission

Time frame: Baseline, 6 hours, 12 hours, and 24 hours after ICU admission

The PaCO₂-EtCO₂ gradient will be calculated as arterial carbon dioxide pressure minus end-tidal carbon dioxide pressure at baseline and at 6, 12, and 24 hours after ICU admission. Change from baseline will be reported for each follow-up time point in mmHg.

Sponsors and collaborators

Lead sponsor

Malatya Egitim Ve Arastirma Hastanesi

Other Gov

Registry information

Important dates

Study start: 2026
Primary completion: 2026
Study completion: 2026
First posted: Jun 17, 2026
Registry last updated: Jun 17, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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