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

August 30, 2026 updated by: Mahmoud Mohamed Ali Abdelhafez, Assiut University

Correlation Between Central Venous and Arterial Blood Gas Parameters Including CO2 Gap in Diabetic and Non-Diabetic Critically Ill Patients

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.

Study Overview

Status

Not yet recruiting

Conditions

Study Type

Observational

Enrollment (Estimated)

100

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

N/A

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.

Description

Inclusion Criteria:

  • 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

Exclusion Criteria:

  • 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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Venous-to-Arterial Carbon Dioxide Tension Difference (Delta PCO2)
Time Frame: Baseline
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

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Assiut University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

October 1, 2026

Primary Completion (Estimated)

October 1, 2027

Study Completion (Estimated)

November 1, 2027

Study Registration Dates

First Submitted

August 30, 2026

First Submitted That Met QC Criteria

August 30, 2026

First Posted (Actual)

September 2, 2026

Study Record Updates

Last Update Posted (Actual)

September 2, 2026

Last Update Submitted That Met QC Criteria

August 30, 2026

Last Verified

August 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • CVBG vs ABG in ICU Diabetics

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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