Purpose of review
To review the mechanistic evidence for early enteral nutrition in critically ill patients within the first week of ICU admission.
There is a lack of recent large randomized controlled trials showing clinically important outcome benefits related to early enteral nutrition. Most supporting studies are based on the animal models, and explore mechanisms of benefit related to gut immunity and oxidative stress. In addition, the impact of nutrient deprivation on the microbiome recently shown in a human trial is compelling. Large randomized controlled clinical trials have emerged in the last 2 years, however, comparing minimal enteral nutrition therapy and enteral nutrition versus parenteral nutrition. They call into question the low quality of clinical evidence and the widespread support for early enteral nutrition as a primary recommendation. As a result, the questions of whether or not enteral nutrition should be initiated in the first week versus standard of care or parenteral nutrition and how clinicians justify this recommendation are raised.
Despite the wide range of quality in the current clinical outcomes evidence, early enteral nutrition within the first week of ICU admission, delivered to the appropriate patient, promotes gut-mediated immunity, lowers metabolic response to stress, maintains microbial diversity, and improves clinical outcomes versus standard of care or parenteral nutrition therapy.