Relation between resting energy expenditure and amino acid metabolism in the post-acute phase of catabolic critically ill patients.

Abstract

Introduction: Post Intensive Care Unit (ICU) acquired weakness is characterized by a massive loss of muscle mass and is generally considered to be multifactorial, secondary to bedridden condition, ubiquitination, increased catabolism, and moderately increased anabolism, and a lack of protein administration. We attended to explore the metabolism of amino acids of long-stayer patients hospitalized for more than 7 days in the ICU, using a stable isotopes technique and correlate the changes observed in the amino acid metabolism to the resting energy expenditure obtained by indirect calorimetry measurement METHODS: Chronically critically ventilated patients were included in the study and matched to healthy volunteers according to age, sex, and BMI. Labeled amino acids were injected, and samples were collected for tracer enrichment and amino acid concentration measurements. Compartment measurement was obtained. In addition, resting energy expenditure was measured by indirect calorimetry, and body composition was measured by bioimpedance. The results were compared to those from normal volunteers.

Results: Fourteen ICU patients were matched to 14 normal volunteers and were very comparable. A high catabolism was observed in these long stayers. Most of the plasma levels of amino acids were decreased in the ICU post-acute phase patients compared to healthy volunteers. Only aspartate, taurine, and hydro methyl butyrate significantly increased. The extracellular pool size of amino acids and whole-body amino acid production was significantly increased compared to normal volunteers. Phase angle was lower and REE was correlated to BMI but inversely correlated to citrulline.

Conclusion: In chronically critically ill patients, catabolism persists. Resting energy expenditure is in a decrease and is inversely correlated to citrulline. Most of plasma amino acid concentrations are decreased, but whole-body amino acid production is increased.