Acid-Base Disturbance, Critically Ill Patients, Indirect Calorimetry
Conditions
Keywords
Bicarbonate, Acid-Base disturbance, Indirect calorimetry
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.
Interventions
Setup of an indirect calorimetry monitor
Sponsors
Hospices Civils de Lyon
Study design
Observational model
COHORT
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Correlation coefficient between the CO₂ production/elimination mismatch assessed by indirect calorimetry and the change in blood bicarbonate over the study period. | 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. |
Countries
France
Contacts
CONTACTRémi SCHWEIZER, Dr
Outcome results
None listed