Bicarbonate Variation Monitoring With Indirect Calorimetry

NCT07782658 | Not Yet Recruiting

• 1 other identifier: 69HCL26_0751
• Study Type: observational
• Target: 91
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Critically Ill Patients; Acid-Base Disturbance; Indirect Calorimetry

Keywords

Bicarbonate; Acid-Base disturbance; Indirect calorimetry

Outcome Measures

Primary Outcomes (1)

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

  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.

  At day 1

Study Arms (1)

Study group

Ventilated patient admitted to intensive care unit

Device: Indirect calorimetry measurement

Interventions

Indirect calorimetry measurement DEVICE

Setup of an indirect calorimetry monitor

Study group

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

Patients admitted to the ICU

You may qualify if:

• 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

You may not qualify if:

• 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
• Frequent disconnections of the ventilator circuit, or planned bronchoscopy before the second bicarbonate measurement

Sponsors & Collaborators

• Hospices Civils de Lyon: lead

Study Sites (1)

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

Bron, Rhone, 69500, France

Location

Central Study Contacts

Rémi SCHWEIZER, Dr

CONTACT

0033472357093; Remi.schweizer@chu-lyon.fr

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: PROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 20, 2026
• First Posted: August 24, 2026
• Study Start (Estimated): November 1, 2026
• Primary Completion (Estimated): November 1, 2027
• Study Completion (Estimated): November 1, 2027
• Last Updated: August 24, 2026

Record last verified: 2026-08

Locations

FR (1)