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NCT Number: NCT07782658

Bicarbonate Variation Monitoring With Indirect Calorimetry

Patients admitted to the intensive care unit frequently exhibit abnormal blood bicarbonate levels. These abnormalities are associated with patient outcomes and often prompt clinicians to modify management, either diagnostically or therapeutically (e.g., initiation or adjustment of mechanical ventilation, initiation or modification of extracorporeal renal replacement therapy, administration of specific diuretics, or sodium bicarbonate infusion).

Currently, the only way to determine blood bicarbonate concentration is through repeated blood sampling for laboratory analysis. However, this method is both discontinuous and invasive.

We have generated an in silico hypothesis suggesting that the mismatch between cellular CO₂ production/elimination and pulmonary CO₂ elimination reflects changes in blood bicarbonate levels. We propose to test this hypothesis in a cohort of intensive care unit patients.

If confirmed, indirect calorimetry could be positioned as a continuous, non-invasive monitoring tool for blood bicarbonate.

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Key information

Conditions

Critically Ill Patients Acid-Base Disturbance Indirect Calorimetry

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

Service d'Anesthésie-Réanimation, Hôpital Louis Pradel, Hospices Civils de Lyon

Bron, Rhone, 69500, France

Location contact

Rémi SCHWEIZER, Dr

CONTACT

[email protected]

0033472357093

Rémi SCHWEIZER, Dr

PRINCIPAL_INVESTIGATOR

Who can participate

Healthy volunteers accepted: No

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

Inclusion criteria

Adult patient admitted to the ICU within the past 72 hours
Receiving invasive mechanical ventilation
For whom the treating clinician plans to perform at least two blood bicarbonate measurements within the next 6 hours
No objection from the participant or their next of kin

Exclusion criteria

Planned weaning from invasive mechanical ventilation or ventilator change before the second bicarbonate measurement
Conditions interfering with the interpretation of indirect calorimetry data:

Inspiratory oxygen fraction > 60%
Administration of inhaled medications, including nitric oxide
Positive end-expiratory pressure (PEEP) > 15 cmH₂O
Excessive leaks in the ventilator circuit, defined as expired volume < 95% of inspired volume
Patient on mechanical circulatory support with a gas exchanger, or planned initiation before the second blood gas analysis
Patient on extracorporeal renal replacement therapy, or planned initiation before the second bicarbonate measurement
Patient who received sodium bicarbonate within 2 hours prior to inclusion, or planned administration before the second bicarbonate measurement
Frequent disconnections of the ventilator circuit, or planned bronchoscopy before the second bicarbonate measurement

Treatment and study plan

Indirect calorimetry measurement

Device

Setup of an indirect calorimetry monitor

Primary outcomes

Correlation coefficient between the CO₂ production/elimination mismatch assessed by indirect calorimetry and the change in blood bicarbonate over the study period.

Time frame: At day 1

CO₂ production/elimination mismatch is estimated using the indirect calorimetry, assuming that the respiratory quotient remains constant throughout the study.

Change in blood bicarbonate is obtained using two consecutive arterial blood samples.

This relationship will be assessed using Pearson's correlation coefficient if assumptions are met (normality and linearity); otherwise, Spearman's coefficient will be used. The correlation coefficient will be reported with its 95% confidence interval and p-value, and the relationship will be illustrated with a scatter plot and regression line or trend curve.

Study contacts

Contact information is provided by the study sponsor or research team.

Rémi SCHWEIZER, Dr

CONTACT

[email protected]

0033472357093

Sponsors and collaborators

Lead sponsor

Hospices Civils de Lyon

Other

Registry information

Official study title

BICARbonate and Indirect Calorimetry Correlation in Critical Care

Acronym: BICAR-CC

Important dates

Study start: 2026
Primary completion: 2027
Study completion: 2027
First posted: Aug 24, 2026
Registry last updated: Aug 24, 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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