Authors: Claude Pichard Taku Oshima Mette M Berger
Publish Date: 2015/01/10
Volume: 41, Issue: 2, Pages: 335-338
Abstract
Survival mechanisms have evolved for thousand of years to optimize vital energydependent functions at the expense of substrates stored in lean and fat tissues A phylogenic analysis of mammalian biology supports the concept that human beings challenged by lifethreatening conditions have been programed for energy autonomy for a few days only as the absence of hydration for 4–5 days defines the survival limit Beyond this limit both water and some energy are needed for further survival and functional recovery In addition only the strongest and youngest individuals were likely to survive as the ultimate goal was the reproduction of the species Energy deficit promotes proteolysis and lipolysis to fuel the mandatory gluconeogenesis which rapidly deteriorates most of the vital body functions eg muscle strength physical mobility thermic control immune response etc This deficit induces autocannibalism a shortterm lifesaving genetically driven mechanism but also a condition compromising recovery and increasing morbidity and ultimately mortality 1 2In 2015 the mean age of ICU patients and the number of those with one or more chronic diseases and/or sarcopenic obesity have significantly increased Life support techniques have increased survival up to a point where the nutritional condition becomes a limiting factor for the clinical outcome A “simple” nutritional support adapted to the body’s needs and enabling a positive response to the sophisticated treatments would be highly desirableThe above considerations largely explain why the early prescription of enteral nutrition EN has been repeatedly associated with improved clinical outcome largely owing to nonnutritional and nutritional benefits 3 Indeed the limited and progressive tolerance to EN observed during the first days after trauma or critical illness favors progressive energy provision which fits the natural evolution of the metabolic stress Enteral nutrition intolerance is frequently observed ie vomiting diarrhea 4 Contrariwise parenteral nutrition PN administered during the early phase of stress often results in unrecognized adverse effects associated with overfeeding because metabolic alterations require careful biological monitoring which is frequently overlooked 5 Discrepancies exist in the literature about the impact of EN and PN on clinical outcome Most of them result from inadequate definition of the energy target delayed use of EN or inappropriate use of PN 6
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