Protein metabolism and requirements

Area of Science:

• Metabolic Adaptations in Critical Illness
• Nutritional Support Strategies

Background:

• Critical illness induces skeletal muscle insulin resistance, accelerated proteolysis, and amino acid efflux.
• This leads to muscle wasting, glutamine depletion, hyperglycemia, and increased morbidity/mortality.
• Protein/amino acid nutrition is crucial for managing metabolic abnormalities in critical illness.

Purpose of the Study:

• To review the role of protein/amino acid nutrition in critical illness.
• To discuss anabolic resistance and factors influencing protein/amino acid requirements.
• To provide evidence-based recommendations for protein/amino acid intake in critically ill patients.

Main Methods:

• Literature review and synthesis of current evidence on protein/amino acid metabolism and nutrition in critical illness.
• Analysis of factors contributing to anabolic resistance, including immobility and physical inactivity.
• Review of established guidelines and research on optimal protein/amino acid dosing.

Main Results:

• Anabolic resistance, a decreased response to protein intake, is common in critical illness.
• Protein/amino acid requirements range from 1.3–1.5 g/kg/day for optimal protein sparing.
• Increased protein needs occur during hypocaloric feeding and in acute renal failure with continuous renal replacement therapy.
• Glutamine supplementation may be necessary in severe systemic inflammatory response.

Conclusions:

• Protein/amino acid nutrition is paramount in critical illness management.
• Addressing anabolic resistance through mobility protocols alongside nutrition is essential.
• Adequate protein intake may be more critical than energy targets for nitrogen balance and patient outcomes.