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Not yet recruitingNCT07799727Updated Sep 2, 2026

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

An observational study in Critical Illness, Diabetes Mellitus and Acid-Base Imbalance, sponsored by Assiut University. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-09-02.

Sponsored by Assiut University · Observational

Study type
Observational
Model
Cohort
Time perspective
Prospective
Enrollment
100
Ages
18 Years and older
Sex
All
01

Study 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.

02

Conditions studied

  • 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
03

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
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.

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

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
04

Study design

Observational model
Cohort
Time perspective
Prospective
Enrollment
100 participants (estimated)
Patient registry
No

Groups and cohorts

  • 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.

05

What researchers measure

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.

    Time frame: Baseline

06

Study locations

No study locations are listed for this record.

07

Registry details

Key details

Study ID
NCT07799727
Lead sponsor
Assiut University
Responsible party
Mahmoud Mohamed Ali Abdelhafez (Resident of Internal Medicine, Assiut University) — Principal investigator
First posted
Sep 2, 2026
Start date
Oct 2026 (estimated)
Primary completion
Oct 2027 (estimated)
Completion
Nov 2027 (estimated)
Last update
Sep 2, 2026
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is not yet recruiting, as verified in Aug 2026. You cannot join it, but the record below documents what was studied.

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