Patients who are unable to eat, require enteral nutrition (preferred over parental nutrition)
There are some formulas that are called "immunonutrition" which try to alter the inflammatory response seen in critical illness
They may contain omega-3 fatty acids and essential amino acids such as arginine or glutamine, and anti-oxidants.
Data
A recent trial (MetaPlus) was designed to see if immunonutrition could decrease the development of infections in the critically ill
Compared to regular high protein formulas, there was no difference in mortality, duration of ventilation, or hospital length of stay
What to do
Immuno-nutrition formulas cannot be routinely recommended
Use regular high protein formulas
Start within 48 hours of identifying a need
References
High-Protein Enteral Nutrition Enriched With Immune-Modulating Nutrients vs Standard High-Protein Enteral Nutrition and Nosocomial Infections in the ICU