Central Venous vs Arterial Blood Gas and CO2 Gap in Critically Ill Patients With and Without Diabetes

NCT07799727 | Not Yet Recruiting

• 1 other identifier: CVBG vs ABG in ICU Diabetics
• Study Type: observational
• Target: 100
• Locations: 0 countries
• Sites: N/A

Brief Summary

Frequent monitoring of acid-base status, ventilation, and tissue oxygenation is essential for managing critically ill patients in the intensive care unit (ICU). While arterial blood gas (ABG) analysis is considered the standard method for these evaluations, maintaining arterial catheters carries risks of complications, such as thrombosis, hematoma, and infection. Central venous blood gas (CVBG) analysis offers a safer alternative because central venous catheters are already routinely placed for patient care. Additionally, the venous-to-arterial carbon dioxide difference (CO2 gap) serves as an indicator of systemic blood flow and tissue perfusion. However, patients with diabetes mellitus often present with underlying microvascular alterations, endothelial changes, and metabolic variations that might alter tissue perfusion and peripheral gas exchange. This study aims to assess the correlation and agreement between central venous and arterial blood gas parameters, as well as evaluate the diagnostic accuracy of the CO2 gap, in diabetic versus non-diabetic critically ill patients. A total of 100 adult ICU patients (50 diabetic and 50 non-diabetic) with pre-existing central venous and arterial lines will be enrolled. Paired blood samples will be drawn simultaneously to compare blood gas values and calculate the CO2 gap without altering standard clinical treatment.

Conditions

Critical Illness; Diabetes Mellitus; Acid-Base Imbalance; Tissue Hypoperfusion

Keywords

Central Venous Blood Gas; Arterial Blood Gas; CO2 Gap; Venous-to-arterial PCO2 Difference; Intensive Care Unit

Outcome Measures

Primary Outcomes (1)

• Venous-to-Arterial Carbon Dioxide Tension Difference (Delta PCO2)

  Delta PCO2 (CO2 gap) is calculated as central venous PCO2 minus arterial PCO2 (PvCO2 - PaCO2) measured in mmHg. Paired arterial and central venous blood gas samples are collected simultaneously and analyzed within 10 minutes.

  Baseline

Study Arms (2)

Diabetic Critically Ill Patients

Critically ill adult patients admitted to the intensive care unit who have a confirmed diagnosis of Diabetes Mellitus. All participants undergo simultaneous paired arterial and central venous blood gas sampling to evaluate agreement and CO2 gap dynamics.

Non-Diabetic Critically Ill Patients

Critically ill adult patients admitted to the intensive care unit without a history or diagnosis of Diabetes Mellitus. All participants undergo simultaneous paired arterial and central venous blood gas sampling to evaluate agreement and CO2 gap dynamics.

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Adult critically ill patients (both diabetic and non-diabetic) admitted to the Critical Care Unit of the Internal Medicine Department at Assiut University Hospital who have standard clinical indications for indwelling central venous catheters and arterial lines.

You may qualify if:

• Adult patients aged 18 years and older
• Critically ill patients admitted to the intensive care unit (ICU)
• Patients with indwelling central venous catheter and arterial line placed for routine clinical management
• Written informed consent obtained from the patient or legal next of kin

You may not qualify if:

• Known severe peripheral vascular occlusive disease affecting line placement
• Use of a pulmonary artery catheter (mixed venous blood line) instead of a standard central venous catheter positioned at the superior/inferior vena cava junction
• Refusal of the patient or legal representative to participate in the study
• Patients younger than 18 years of age

Sponsors & Collaborators

• Assiut University: lead

MeSH Terms

Conditions

Critical Illness; Diabetes Mellitus; Acid-Base Imbalance

Condition Hierarchy (Ancestors)

Disease Attributes; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Glucose Metabolism Disorders; Metabolic Diseases; Nutritional and Metabolic Diseases; Endocrine System Diseases

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Resident of Internal Medicine

Study Record Dates

• First Submitted: August 30, 2026
• First Posted: September 2, 2026
• Study Start: October 1, 2026
• Primary Completion (Estimated): October 1, 2027
• Study Completion (Estimated): November 1, 2027
• Last Updated: September 2, 2026

Record last verified: 2026-08