Toward nutrition improving outcome of critically ill patients:
How to interpret recent feeding RCTs?
by Jan Gunst,
Michael P. Casaer, Jean-Charles Preiser, Jean Reignier and Greet Van den Berghe
Critical Care volume 27,
Article number: 43 Published: 27
January 2023
Abstract
Although numerous observational studies associated
underfeeding with poor outcome, recent randomized controlled trials (RCTs) have
shown that early full nutritional support does not benefit critically ill
patients and may induce dose-dependent harm. Some researchers have suggested
that the absence of benefit in RCTs may be attributed to overrepresentation of
patients deemed at low nutritional risk, or to a too low amino acid versus
non-protein energy dose in the nutritional formula. However, these hypotheses
have not been confirmed by strong evidence. RCTs have not revealed any subgroup
benefiting from early full nutritional support, nor benefit from increased
amino acid doses or from indirect calorimetry-based energy dosing targeted at
100% of energy expenditure. Mechanistic studies attributed the absence of
benefit of early feeding to anabolic resistance and futile catabolism of extra
provided amino acids, and to feeding-induced suppression of recovery-enhancing
pathways such as autophagy and ketogenesis, which opened perspectives for
fasting-mimicking diets and ketone supplementation. Yet, the presence or
absence of an anabolic response to feeding cannot be predicted or monitored and
likely differs over time and among patients. In the absence of such monitor,
the value of indirect calorimetry seems obscure, especially in the acute phase
of illness. Until now, large feeding RCTs have focused on interventions that
were initiated in the first week of critical illness. There are no large RCTs
that investigated the impact of different feeding strategies initiated after
the acute phase and continued after discharge from the intensive care unit in
patients recovering from critical illness.
