With respect to hypocaloric enteral nutrition in the critically ill:
a) Explain the following terms:
i. Trophic feeding
ii. Permissive underfeeding
Outline the potential advantages of hypocaloric enteral nutrition and the available evidence for its use. (60% marks)
Trophic feeding refers to enteral feeding below the minimum required caloric intake, with the aim of maintaining gut integrity rather than meeting patient’s nutritional requirements. Definition of volume feed/energy required varies. Between 10-30ml/hr or 15-25% of calculated caloric intake. Can’t be used as sole nutritional strategy long term.
Permissive underfeeding is the provision of a reduced non-protein caloric target (around 40-60% of calculated total) hypothesing that lower non-protein calorie intake may be beneficial. May be used as sole nutritional strategy.
Advantages of trophic feeding
Include potential beneficial effects on the gut such as preserving intestinal epithelium, stimulating secretion of brush border enzymes, enhancing immune function, preserving epithelial tight cell junctions, and preventing bacterial translocation. Could be considered in patients unable to tolerate full enteral nutrition. May minimise complications associated with full enteral feeding such as feed intolerance, aspiration, high gastric volumes, and diarrhoea.
Available evidence for trophic feeding
2 RCT’s of patients with respiratory failure/ARDS (largest = EDEN trial JAMA 2012)
Advantages of permissive underfeeding
Available evidence for permissive underfeeding:
Specific trials not needed for pass.
Additional Examiners Comments:
This question was answered poorly. The majority of candidates were unable to accurately describe or define the two feeding strategies. There was limited appreciation of the available evidence
Trophic feeding: Sondheimer et al (2004); "The generally accepted definition of trophic feeding is a small volume of balanced enteral nutrition insufficient for the patient's nutritional needs but producing some positive gastrointestinal or systemic benefit."
Permissive underfeeding: The systematic review by Owais et al (2010) reveals a massive variation of historical definitions, ranging though 13-14 kcal/kg/day, <20 kcal/kg/day, 1000 kcal/day, or <33% of estimated requirement, or 5,000-10,000 kcal/week. The college used the 40-60% goal from Arabi et al (2015). The distinction is that this a nutritional strategy, rather than one focused on intestinal mucosal health.
Advantages of permissive underfeeding:
Evidence for permissive underfeeding:
Advantages of trophic feeding:
Evidence for trophic feeding:
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