Nutrition in Critical illness 

1. Factors Contributing to Nutritional Impairment in Critical Illness 
Critical illness significantly affects nutrition due to metabolic, physiological, and practical factors. Key contributors include: 

A. Hypermetabolism & Catabolism 
Increased energy expenditure due to stress response. 
Elevated protein breakdown → muscle wasting, negative nitrogen balance. 
Causes: sepsis, burns, trauma, major surgery. 

B. Inflammation & Hormonal Changes 
Cytokine release (TNF-α, IL-1, IL-6) → anorexia, insulin resistance, increased gluconeogenesis. 
Stress hormones (cortisol, catecholamines) → protein catabolism and lipolysis. 

C. Reduced Oral Intake 
Sedation, mechanical ventilation, altered consciousness. 
Gastrointestinal dysfunction: nausea, vomiting, ileus, diarrhoea. 

D. Medical Interventions 
Fasting for procedures, imaging, surgery. 
Certain medications: opioids, vasopressors, prokinetic agents affecting GI motility. 

E. Pre-existing Conditions 
Chronic illnesses (CKD, liver disease, malignancy) → baseline malnutrition. 
Elderly patients at higher risk due to sarcopenia. 

2. Nutritional Assessment Tools in the ICU 

Early assessment is essential to guide nutrition therapy. Common tools include: 

A. Subjective Tools 

Subjective Global Assessment (SGA): Considers weight loss, intake, GI symptoms, functional capacity, physical exam. 

Nutrition Risk in Critically Ill (NUTRIC) Score: Specifically developed for ICU; considers age, APACHE II, SOFA, comorbidities, days from hospital to ICU admission, IL-6 (optional). 

B. Anthropometric & Biochemical Measures 

Weight, BMI, mid-arm circumference (difficult in ICU due to oedema). 
Serum albumin/pre-albumin (limited reliability in acute illness). 

C. Functional Measures 

Handgrip strength (if feasible, often limited in ICU). 

Key: NUTRIC score is widely used to identify patients who benefit most from aggressive nutrition support. 

3. Nutritional Care Bundles in ICU 

Bundles are structured protocols to optimize nutrition: 

Components of ICU Nutrition Bundles 

Early initiation of nutrition (ideally within 24–48 hours of ICU admission). 
Prefer enteral feeding over parenteral (if gut functional). 
Protocolised feeding: stepwise advancement to meet calorie/protein targets. 
Monitoring tolerance: gastric residuals, abdominal distension, diarrhoea. 
Glycaemic control and micronutrient supplementation. 
Multidisciplinary involvement: dietitian, physician, nurse, pharmacist. 

Goal: Reduce underfeeding, prevent complications like refeeding syndrome, maintain gut integrity. 

4. Types of Feeding in Critical Illness 

A. Enteral Nutrition (EN) – preferred if GI tract functional 

Nasogastric (NG) Tube 
Indications: short-term feeding (<4–6 weeks), functional stomach. 
Advantages: easy placement, low cost. 
Limitations: aspiration risk, reflux, discomfort. 

Nasojejunal (NJ) Tube 
Indications: impaired gastric emptying, high aspiration risk, pancreatitis. 
Advantage: bypass stomach → reduced aspiration. 
Limitations: more complex insertion, often needs imaging or endoscopy. 

Percutaneous Endoscopic Gastrostomy (PEG) 
Indications: long-term feeding (>4–6 weeks), intact gut. 
Advantages: stable, less discomfort, lower dislodgement risk. 
Limitations: requires endoscopy, infection risk. 

Radiologically Inserted Gastrostomy (RIG) 
Similar to PEG but placed under imaging guidance (when endoscopy not possible). 

Enteral feeding formulas: 

Standard polymeric: intact protein, carbs, fats. 
Semi-elemental: partially hydrolysed for malabsorption. 
Disease-specific: renal, hepatic, diabetes-specific formulas. 

B. Parenteral Nutrition (PN) 

Indications: 
Non-functional gut (ileus, bowel obstruction, severe pancreatitis, high-output fistula). 
When Enteral Nutrition is contraindicated or insufficient. 
Components: glucose, amino acids, lipids, electrolytes, vitamins, trace elements. 
Risks: infection, metabolic complications, liver dysfunction. 
Timing: Usually after 7 days if EN not possible; earlier if malnourished. 

C. Oral Nutrition 
For patients able to swallow and tolerate oral intake. 
Supplements: 
High-protein, high-calorie oral nutritional supplements. 
Fortified meals, modular additions. 
Note: Oral intake is often insufficient in ICU; monitoring intake is critical. 

5. Practical Considerations 

Early feeding: Early EN is associated with improved outcomes (reduced infections, gut mucosal atrophy, better nitrogen balance). 
Protein targets: Critically ill often require 1.2–2 g/kg/day. 
Energy targets: ~25–30 kcal/kg/day, adjusted for metabolic stress. 
Monitoring: Daily assessment of tolerance, labs (electrolytes, glucose, liver, renal), weight, nitrogen balance. 

Summary