Critical IllnessIAAO-ICNCT06104527
Indicator Amino Acid Oxidation in ICU Patients
A study testing Standard protein enteral nutrition with enteral tracer and High protein enteral nutrition with enteral tracer in people with Critical Illness and Muscle Wasting, run by Maastricht University Medical Center at 1 site in Netherlands.
Trial summary
This study will use the indicator amino acid oxidation technique (IAAO) to determine protein oxidation of ICU patients at two protein intakes: 1.3 g/kg/d versus 2.0 g/kg/d. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Critical Illness, Muscle Wasting
- What is being tested?
- Standard protein enteral nutrition with enteral tracer and High protein enteral nutrition with enteral tracer
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 8 participants
- Where
- 1 siteNetherlands
- Study dates
- 30 Oct 2023to 23 Mar 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- ≥ 18 years old
- Unplanned admission to the ICU
- Mechanically ventilated
- Start of enteral nutrition within 2 days of intubation
- ≥ 3 days on enteral nutrition
- Expected remaining ICU stay on mechanical ventilation of ≥ 2 days
Who cannot join
- Contra-indication for enteral nutrition at the discretion of the treating physician
- Feeding intolerance during incremental feeding protocol
- Moribund or withholding of treatment
- On extracorporeal membrane oxygenation (ECMO)
- Presence of chest drains, pneumothorax, tracheoesophageal fistula or subcutaneous emphysema
- Kidney failure AND a "no dialysis"-code on admission
- Hepatic encephalopathy (West Haven criteria 3-4)
- BMI < 18 kg/m2
Trial locations and contacts
1 site in 1 country.
Netherlands1 site
Maastricht University Medical Center+
Maastricht, Limburg, 6229 HX
About this study
Official title: The Effect of Standard or Higher Protein Feeding on Indicator Amino Acid Oxidation in ICU Patients
This study will use the indicator amino acid oxidation technique (IAAO) to determine protein oxidation of ICU patients at two protein intakes: 1.3 g/kg/d versus 2.0 g/kg/d.
Read the detailed description
Rationale:
While protein administration guidelines for critical care are available from international organizations such as ASPEN and ESPEN, they vary greatly in their recommended dose and are based on relatively low-quality evidence. The Indicator Amino Acid Oxidation (IAAO) technique has been developed as a more practical and non-invasive tool to assess protein metabolism that can be used in vulnerable populations. Application of the IAAO technique in patients admitted to the Intensive Care Unit (ICU) could provide an alternative to better investigate optimal protein feeding during critical illness.
Objective:
To assess the effect of enteral feeding with higher protein content compared to standard protein content on indicator amino acid oxidation in ICU patients.
Study design:
Randomized, counterbalanced, cross-over trial.
Study population:
Adult patients with an unplanned admission to the ICU, who are mechanically ventilated and have an indication for prolonged enteral nutrition.
Intervention:
Subjects will undergo two test days in randomized order during which they receive either enteral feeding according to a standard protein dose (1.3 g/kg/d) or a higher protein dose (2.0 g/kg/d). Continuous feeding of L-[1-13C]-phenylalanine combined with breath, urine and blood samples will be applied to assess indicator amino acid oxidation.
Main study parameters/endpoints:
The primary endpoint is indicator amino acid oxidation after enteral feeding with a standard or higher protein content, determined using the Indicator Amino Acid Oxidation (IAAO) method by measuring 13CO2 enrichment in expired breath and enrichment of L-[1-13C]-phenylalanine in plasma and urine.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
The overall risk of the study is negligible. The current study compares the effect of two nutritional compositions, that fall within the recommendations of international guidelines on ICU nutrition, on protein metabolism following ICU admission. To avoid overfeeding in the early phase of critical illness, both in terms of calories and protein, full enteral nutrition is provided after three days of gradual increase of intake (i.e., 25-50-75% of targeted intake, on days 1-2-3 respectively). Sampling of breath, urine, feces and plasma does not bring additional risks for this population. Our department has an extensive background in amino acid stable isotope methodology, assessment of 13CO2 enrichment in expired breath samples, and assessment of carbon dioxide production by indirect calorimetry.
- Conditions
- Critical Illness, Muscle Wasting
- Being tested
- Standard protein enteral nutrition with enteral tracer, High protein enteral nutrition with enteral tracer
- Keywords
- Dietary Protein, Enteral Nutrition
- Medical subject headings
- Critical Illness, Muscular Atrophy
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Standard protein enteral nutrition with enteral tracerCombination product
Enteral nutrition with standard (1.3 g/kg/d) protein provision, given via a nasogastric tube. An oral L-[1-13C]-phenylalanine tracer is given as co-intervention. Use of an enterally given tracer is necessary to determine indicator amino acid oxidation.
High protein enteral nutrition with enteral tracerCombination product
Enteral nutrition with high (2.0 g/kg/d) protein provision, given via a nasogastric tube. An oral L-[1-13C]-phenylalanine tracer is given as co-intervention. Use of an enterally given tracer is necessary to determine indicator amino acid oxidation.
| Study group | Role | What they receive |
|---|---|---|
| 1.3 g/kg/day followed by 2.0 g/kg/day | Other | Patients in this arm will, on their first test day, receive enteral nutrition containing 1.3 grams of protein per kg of body weight per day followed by 2.0 grams of protein per kg of body weight per day on their second test day. Receives: Combination Product: Standard protein enteral nutrition with enteral tracer; Combination Product: High protein enteral nutrition with enteral tracer |
| 2.0 g/kg/day followed by 1.3 g/kg/day | Other | Patients in this arm will, on their first test day, receive enteral nutrition containing 2.0 grams of protein per kg of body weight per day followed by 1.3 grams of protein per kg of body weight per day on their second test day. Receives: Combination Product: Standard protein enteral nutrition with enteral tracer; Combination Product: High protein enteral nutrition with enteral tracer |
What is being measured
The primary outcome is the main question the study is designed to answer.
Indicator amino acid oxidation
Indicator amino acid oxidation expressed as µmol/kg/h
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission.
Secondary outcomes (7)
13CO2 excretion in breath (F13CO2)
Collected using breath samples; measured using gas chromatography-mass spectrometry (Agilent G1530N/G2589A, Little Falls, USA)
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Enrichments of plasma L-[1-13C]-phenylalanine
Collected via in situ arterial catheter; measured using gas chromatography-mass spectrometry (Agilent G1530N/G2589A, Little Falls, USA)
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Enrichments of urine L-[1-13C]-phenylalanine
Collected via indwelling urinary catheter; measured using gas chromatography-mass spectrometry (Agilent G1530N/G2589A, Little Falls, USA)
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Concentration of plasma phenylalanine
Collected via in situ arterial catheter; analyzed using high performance liquid chromatography
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Fecal output and fecal protein content
Collected via in situ fecal collection bag; protein content in fecal samples will be measured using Dumas method (Variomax CN-analyser)
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected from start of intervention until end of intervention & tracer protocol.
Enrichment of breath 13CO2
Collected using breath samples; measured using gas chromatography-mass spectrometry (Agilent G1530N/G2589A, Little Falls, USA)
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
CO2 production
Measured using indirect calorimetry
Measured: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected 2 hours after start of tracer protocol.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Oct 2023
- Study start30 Oct 2023
- Primary completion23 Mar 2026
- Study completion23 Mar 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Critical IllnessStudies of the same condition, open and under way.
- More trials run by Maastricht University Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Diagnosis
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Enrolment
- 8 participants (actual)
Sponsor and investigators
- Lead sponsor
- Maastricht University Medical Center
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Luc van Loon, Ph.D., Principal investigator, Maastricht University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06104527
- Sponsor's protocol ID
- NL84098.000.23
- Acronym
- IAAO-IC
- Status last verified
- Apr 2026
- First submitted
- 18 Oct 2023
- Last updated
- 17 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: Study data can be made available upon reasonable request, which will be considered by the project investigators (Drs. Julia Bels, Dr. Jorn Trommelen) and the Principal Investigator (Prof. Dr. Luc van Loon). A request for data-sharing together with a developed study protocol are prerequisites for consideration.
Study at a glance
From the registry record, last updated by the sponsor on 17 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- The Effect of Standard or Higher Protein Feeding on Indicator Amino Acid Oxidation in ICU Patients
- ClinicalTrials.gov ID
- NCT06104527
- Acronym / sponsor ID
- IAAO-IC / NL84098.000.23
- Conditions
- Critical Illness, Muscle Wasting
- Keywords
- Dietary Protein, Enteral Nutrition
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 8 participants (actual)
- Lead sponsor
- Maastricht University Medical CenterUniversity, hospital or other
- Study start
- 30 Oct 2023 (actual)
- Primary completion
- 23 Mar 2026 (actual)
- Study completion
- 23 Mar 2026 (actual)
- First posted
- 27 Oct 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study will use the indicator amino acid oxidation technique (IAAO) to determine protein oxidation of ICU patients at two protein intakes: 1.3 g/kg/d versus 2.0 g/kg/d.
Detailed description
Rationale:
While protein administration guidelines for critical care are available from international organizations such as ASPEN and ESPEN, they vary greatly in their recommended dose and are based on relatively low-quality evidence. The Indicator Amino Acid Oxidation (IAAO) technique has been developed as a more practical and non-invasive tool to assess protein metabolism that can be used in vulnerable populations. Application of the IAAO technique in patients admitted to the Intensive Care Unit (ICU) could provide an alternative to better investigate optimal protein feeding during critical illness.
Objective:
To assess the effect of enteral feeding with higher protein content compared to standard protein content on indicator amino acid oxidation in ICU patients.
Study design:
Randomized, counterbalanced, cross-over trial.
Study population:
Adult patients with an unplanned admission to the ICU, who are mechanically ventilated and have an indication for prolonged enteral nutrition.
Intervention:
Subjects will undergo two test days in randomized order during which they receive either enteral feeding according to a standard protein dose (1.3 g/kg/d) or a higher protein dose (2.0 g/kg/d). Continuous feeding of L-[1-13C]-phenylalanine combined with breath, urine and blood samples will be applied to assess indicator amino acid oxidation.
Main study parameters/endpoints:
The primary endpoint is indicator amino acid oxidation after enteral feeding with a standard or higher protein content, determined using the Indicator Amino Acid Oxidation (IAAO) method by measuring 13CO2 enrichment in expired breath and enrichment of L-[1-13C]-phenylalanine in plasma and urine.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
The overall risk of the study is negligible. The current study compares the effect of two nutritional compositions, that fall within the recommendations of international guidelines on ICU nutrition, on protein metabolism following ICU admission. To avoid overfeeding in the early phase of critical illness, both in terms of calories and protein, full enteral nutrition is provided after three days of gradual increase of intake (i.e., 25-50-75% of targeted intake, on days 1-2-3 respectively). Sampling of breath, urine, feces and plasma does not bring additional risks for this population. Our department has an extensive background in amino acid stable isotope methodology, assessment of 13CO2 enrichment in expired breath samples, and assessment of carbon dioxide production by indirect calorimetry.
Study design
- Primary purpose
- Diagnosis
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| 1.3 g/kg/day followed by 2.0 g/kg/day | Other | Combination Product: Standard protein enteral nutrition with enteral tracer, Combination Product: High protein enteral nutrition with enteral tracerPatients in this arm will, on their first test day, receive enteral nutrition containing 1.3 grams of protein per kg of body weight per day followed by 2.0 grams of protein per kg of body weight per day on their second test day. |
| 2.0 g/kg/day followed by 1.3 g/kg/day | Other | Combination Product: Standard protein enteral nutrition with enteral tracer, Combination Product: High protein enteral nutrition with enteral tracerPatients in this arm will, on their first test day, receive enteral nutrition containing 2.0 grams of protein per kg of body weight per day followed by 1.3 grams of protein per kg of body weight per day on their second test day. |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (6 listed)
- ≥ 18 years old
- Unplanned admission to the ICU
- Mechanically ventilated
- Start of enteral nutrition within 2 days of intubation
- ≥ 3 days on enteral nutrition
Key exclusion criteria (8 listed)
- Contra-indication for enteral nutrition at the discretion of the treating physician
- Feeding intolerance during incremental feeding protocol
- Moribund or withholding of treatment
- On extracorporeal membrane oxygenation (ECMO)
- Presence of chest drains, pneumothorax, tracheoesophageal fistula or subcutaneous emphysema
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Standard protein enteral nutrition with enteral tracerEnteral nutrition with standard (1.3 g/kg/d) protein provision, given via a nasogastric tube. An oral L-[1-13C]-phenylalanine tracer is given as co-intervention. Use of an enterally given tracer is necessary to determine indicator amino acid oxidation. | Combination product | 1.3 g/kg/day followed by 2.0 g/kg/day, 2.0 g/kg/day followed by 1.3 g/kg/day |
| High protein enteral nutrition with enteral tracerEnteral nutrition with high (2.0 g/kg/d) protein provision, given via a nasogastric tube. An oral L-[1-13C]-phenylalanine tracer is given as co-intervention. Use of an enterally given tracer is necessary to determine indicator amino acid oxidation. | Combination product | 1.3 g/kg/day followed by 2.0 g/kg/day, 2.0 g/kg/day followed by 1.3 g/kg/day |
Primary outcome
Indicator amino acid oxidation
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission.
Indicator amino acid oxidation expressed as µmol/kg/h
7 secondary outcomes
13CO2 excretion in breath (F13CO2)
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Enrichments of plasma L-[1-13C]-phenylalanine
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Enrichments of urine L-[1-13C]-phenylalanine
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Concentration of plasma phenylalanine
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
Fecal output and fecal protein content
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected from start of intervention until end of intervention & tracer protocol.
Enrichment of breath 13CO2
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected before start of tracer and at end of tracer protocol.
CO2 production
Time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission. Per test day: collected 2 hours after start of tracer protocol.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 17 Apr 2026.
- Individual participant dataSharing planned: Yes. Study data can be made available upon reasonable request, which will be considered by the project investigators (Drs. Julia Bels, Dr. Jorn Trommelen) and the Principal Investigator (Prof. Dr. Luc van Loon). A request for data-sharing together with a developed study protocol are prerequisites for consideration.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Luc van Loon, Ph.D. principal investigator
Maastricht University
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Standard protein enteral nutrition with enteral tracer and High protein enteral nutrition with enteral tracer in people with Critical Illness and Muscle Wasting, run by Maastricht University Medical Center at 1 site in Netherlands.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 6 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 17 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Netherlands. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Indicator amino acid oxidation (time frame: Collected at standard vs higher protein administration, on test day 1 and 2 (depending on randomisation order), during the first week of ICU admission.). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 17 Apr 2026.