Protein and the critically ill; do we know what to give?

Area of Science:

• Clinical Nutrition
• Critical Care Medicine
• Metabolic Support

Background:

• National Institute for Health and Clinical Excellence (NICE) recommends 50% target energy/protein for critically ill patients.
• This NICE guideline results in lower initial nitrogen (N) provision (0.12 g N/kg/day) compared to other expert recommendations (~0.25 g N/kg/day).
• Higher N provision is traditionally thought to reduce catabolism and lean tissue wasting.

Purpose of the Study:

• To evaluate the current recommendations for nutrition support in critically ill patients.
• To question the assumption that improved nitrogen balance directly correlates with better clinical outcomes.
• To explore alternative initial feeding strategies for critically ill individuals.

Main Methods:

• Review of existing literature and expert recommendations on nutrition support in critical illness.
• Analysis of teleological arguments and studies questioning the link between N balance and clinical progress.
• Consideration of evidence suggesting improved survival with lower initial energy and N intakes.

Main Results:

• Concerns exist regarding the NICE recommendation's low initial N provision.
• Evidence suggests that lower initial energy and N intakes may improve survival in critical illness.
• The assumption that optimal N balance equates to optimal clinical outcome is challenged.

Conclusions:

• Modest initial nutrition support levels appear logical for seriously ill patients.
• Further research is needed to compare clinical benefits of different energy and N feeding strategies.
• Investigating specialized amino acid formulations for critical illness is warranted.