Respiratory Quotient and Phosphate Changes During Early Critical Illness
Trial statusNot yet recruiting
Trial phaseNot listed
Trial typeObservational
Biological sexAll
Age18+
SponsorVastra Gotaland Region
About this trial
Critically ill patients often experience major changes in metabolism during the first days of intensive care. When nutrition is started or increased after a period of reduced intake, some patients may develop refeeding syndrome, a potentially serious condition associated with shifts in electrolytes such as phosphate, potassium, and magnesium.
This study will investigate whether changes in respiratory quotient (RQ), measured by indirect calorimetry, are associated with changes in serum phosphate during the first intensive care week. RQ reflects the balance between oxygen consumption and carbon dioxide production and provides information about which energy substrates are being used by the body. A rising RQ may indicate increasing carbohydrate metabolism and could potentially provide an early physiological marker of metabolic changes associated with refeeding.
Mechanically ventilated adult intensive care patients will undergo daily indirect calorimetry during the first five days of the study period, with an additional measurement on day 7 when feasible. Serum phosphate and other electrolytes, nutritional intake, insulin treatment, ventilator parameters, and relevant physiological variables will be recorded at corresponding time points.
The study will also evaluate how well established screening criteria for refeeding risk, including the NICE criteria, identify patients who subsequently develop metabolic changes consistent with refeeding. No study-specific changes to nutrition or other treatment will be made.
This accurately reflects the observational nature of the study: routine IC, laboratory and nutritional data are collected without changing treatment.
Eligibility criteria
This trial does not accept healthy volunteersQualifiers
Age 18 years or older.
Admitted to the central intensive care unit (CIVA) or neurointensive care unit (NIVA) at Sahlgrenska University Hospital.
Receiving invasive mechanical ventilation.
Expected intensive care stay longer than 72 hours.
Disqualifiers
Ongoing or planned continuous renal replacement therapy or intermittent - hemodialysis (CRRT/iHD).
Extracorporeal membrane oxygenation (ECMO).
Fraction of inspired oxygen (FiO2) >0.70.
Severe renal failure or rapidly increasing creatinine without dialysis, where phosphate levels may not adequately reflect metabolic changes.
Trial population
Adult patients admitted to the central intensive care unit (CIVA) or neurointensive care unit (NIVA) at Sahlgrenska University Hospital who are receiving invasive mechanical ventilation, have an expected ICU stay of more than 72 hours, and have enteral or parenteral nutrition started or planned. Eligible patients are identified prospectively during routine daily ICU screening and included according to predefined inclusion and exclusion criteria.
Trial design
Design model
Cohort
Time perspective
Prospective
Treatments tested in this trial
Nutritional Exposure During Early Critical Illness
Other interventionEnteral and/or parenteral nutrition is provided according to usual clinical care. Energy intake, carbohydrate intake, protein intake, fat intake, and changes in nutritional delivery are recorded prospectively to evaluate their relationship with respiratory quotient, serum phosphate, and other metabolic variables. No nutrition strategy is assigned by the study.
Treatment groups
40 Participants
are divided into 1 treatment groupGroup A: Prospective ICU Cohort1 intervention
Trial outcomes
Primary outcomes
1
Within-Participant Regression Coefficient for Respiratory Quotient Versus Serum Phosphate Concentration
Respiratory quotient (RQ) will be calculated from indirect calorimetry as VCO2/VO2, and serum phosphate will be measured in mmol/L. The primary outcome will be the within-participant regression coefficient describing the change in RQ associated with a 0.1 mmol/L change in serum phosphate concentration, estimated using a linear mixed-effects model with participant as a random effect. The model will account for repeated measurements and prespecified covariates including energy intake, carbohydrate intake, insulin treatment, PaCO2, and body temperature.
Time frame
Daily on study days 1-5, with an additional measurement on day 7 when feasibleSecondary outcomes
1
Sensitivity of NICE Refeeding Risk Criteria for Prespecified Metabolic Changes
Participants will be classified as being at risk or not at risk of refeeding syndrome according to NICE criteria at initiation of nutritional therapy. Sensitivity will be calculated as the proportion of participants who develop the prespecified metabolic pattern and who were classified as at risk according to NICE criteria at baseline.
Time frame
From initiation of nutrition through study day 5, with follow-up through day 7 when available2
Specificity of NICE Refeeding Risk Criteria for Prespecified Metabolic Changes
Participants will be classified as being at risk or not at risk of refeeding syndrome according to NICE criteria at initiation of nutritional therapy. Specificity will be calculated as the proportion of participants who do not develop the prespecified metabolic pattern and who were correctly classified as not at risk according to NICE criteria at baseline. The prespecified metabolic pattern is defined as respiratory quotient (RQ) ≥0.90 together with a decrease in serum phosphate of at least 0.16 mmol/L during follow-up.
Time frame
From initiation of nutrition through study day 5, with follow-up through day 7 when available3
Number of Participants With RQ ≥0.90 and Serum Phosphate Decrease ≥0.16 mmol/L
The number and proportion of participants who develop both a respiratory quotient (RQ) ≥0.90 and a decrease in serum phosphate of at least 0.16 mmol/L during follow-up will be reported. The timing of the two changes relative to each other will also be described.
Time frame
Daily during study days 1-5, with an additional assessment on day 7 when feasibleLocations
Sponsors and contacts
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Source ClinicalTrials.gov
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