Study Guide: Nutrition Therapy in Critically Ill Adults

Why this matters in the ICU

Critical illness is a profoundly catabolic state. During sepsis, trauma, ARDS, major surgery, or shock, patients develop inflammation, insulin resistance, accelerated proteolysis, gut barrier dysfunction, and rapid skeletal muscle loss.

For us in PCCM, nutrition is not just “tube feeds.” It is supportive therapy that has to match the phase of illness. The wrong dose at the wrong time can worsen GI complications, overfeeding, hyperglycemia, refeeding syndrome, and possibly outcomes.

The central lesson from modern ICU nutrition trials is that early aggressive feeding is not clearly beneficial in the acute phase, and in some groups it may cause harm.

1. Phases of critical illness

Early acute phase

Usually the first few days of ICU illness.

Physiology:

• High inflammation
• High endogenous glucose production
• Insulin resistance
• Severe catabolism
• Gut dysmotility and barrier dysfunction
• Limited ability to use exogenous calories/protein effectively

Nutrition goal:

• Start cautiously
• Support gut integrity
• Avoid overfeeding