Nutrient Uptake During Continuous Enteral Feeding

Study Overview
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Brief Summary
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Continuous enteral nutrition is used to feed patients in intensive care who are unable to eat normally. The goal of this observational study is to learn about the uptake of nutrients from feeding formula. The study method will first be applied in healthy persons to establish workability and normal values, then in patients in the intensive care unit to learn how nutrient uptake is affected by critical illness. The main questions this study aims to answer are: what is the time course of uptake of phenylalanine (an amino acid) and glucose (a sugar) from enteral feeding formula given continuously over several hours what is the time course of the filling volume of the stomach during continuous enteral feeding Participants receive feeding formula through a nasogastric feeding tube and blood samples are taken at short intervals to analyse uptake of nutrients into blood. Simultaneously, the filling volume of the stomach is measured by gastric ultrasound.

Detailed Description
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Background The investigators have previously studied the uptake of dietary isotope-labeled phenylalanine and plasma amino acid concentrations in critically ill patients and healthy subjects. During continuous feeding, uptake was unexpectedly found to be highly variable over time. Due to infrequent sampling, the time course of variability could not be modeled mathematically. Also, the underlying physiological mechanisms remain unclear, though it is hypothesized that gastric emptying is a major factor determining temporal variability. The study here described is a follow-up that includes serial abdominal ultrasound studies to measure gastric emptying, additional indicators/tracers to determine more detail of uptake vs. digestion/transport/metabolism, and makes use of more frequent sampling to allow for detailed mathematical modeling of temporal variability. Experimental protocol ICU patients: Standard care and treatment as per clinical routines Pre-experiment ongoing nutrition for ≥ 6 hrs by nasogastric feeding tube or gastrostomy (not postpyloric) Bed rest during experiment as feasible Healthy subjects Keep dietary and training habits for ≥ 2 days before experiment start Overnight fast Bed rest during experiment as feasible Nasogastric feeding tube Arterial line in radial or ulnar artery Nutrition, sampling, measurements Experimental nutrition by continuous infusion for 10 hrs Infusion rate corresponding to 25 kcal/kg body weight/day (calculated including metabolizable tracers/indicators) Arterial blood sampling (à 1 ml) every 5 min in pilot study (may adjust to 10 or 15 min depending on results of pilot study) Serial abdominal ultrasound for determination of gastric volume (pilot study will determine how often) Experimental nutrition Commercially available feeding formula for ICU use (Fresubin® HP Energy or similar) with added phenylalanine and glucose indicators Intrinsically labeled protein: 13C-L-phenylalanine intrinsically labeled milk protein Nonmetabolisable phenylalanine analogue: D-phenylalanine Free amino acid tracer: stable isotope-labeled phenylalanine tracer (2H5-L-Phe) Non-metabolizable glucose analogue: 3-O-Methyl-d-glucose (3-OMG) Free glucose tracer: isotope labeled D-glucose Analyses arterial plasma amino acid and glucose tracers as above arterial plasma 3-OMG arterial plasma aminograms arterial plasma glucose, insulin, c peptide

Official Title
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Uptake of Glucose and Phenylalanine From Continuous Enteral Nutrition in Healthy and Critically Ill Persons

Conditions
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Critical Illness

Intervention / Treatment
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* Procedure: Continuous enteral feeding


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria (ICU patients): - stable enteral nutrition of >80% of measured or calculated energy expenditure by nasogastric feeding tube or gastrostomy Exclusion Criteria (ICU patients): enteral nutrition by postpyloric route such as jejunostomy or postpyloric tube remaining ICU stay expected < 12 hrs ongoing bleeding that requires surgery/intervention or transfusion of > 2 units red cells/24 hrs inability to use feeding tube or arterial line Inclusion Criteria (healthy subjects): - healthy volunteer Exclusion Criteria (healthy subjects) - any condition or medication affecting nutrition or metabolism

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Healthy subjects<br>Healthy persons ≥ 18 yrs of age | Procedure: Continuous enteral feeding<br>* Enteral nutrition by continuous infusion for 10 hrs at a dose corresponding to 25 kcal/kg body weight/day<br>* Other names: Gastric ultrasound;|
| Critically ill patients<br>Critically ill patients ≥ 18 yrs of age admitted to the ICU | Procedure: Continuous enteral feeding<br>* Enteral nutrition by continuous infusion for 10 hrs at a dose corresponding to 25 kcal/kg body weight/day<br>* Other names: Gastric ultrasound;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Glucose and phenylalanine indicators | Time series of isotopic and non-isotopic indicators of glucose and phenylalanine from enteral nutrition | 0-10 hours | 
| Gastric volume | Time series of gastric volume | 0-10 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Plasma metabolites | Time series of plasma aminograms, glucose, insulin and c peptide | 0-10 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Continuous enteral feeding, Gastric volume, Intestinal absorption, Enteral nutrition, Nutritional support