Nutrition – EN/PN

Master answer

Enteral feeding in critically ill

• Primary goal to alter course and outcome of critical illness
• Major goals determined by following principles:
  • Catabolism > anabolism. Calorie consumption reduced with better management of critical illness
  • Carbohydrates preferred as fat mobilization impaired
  • Protein: mitigate breakdown of muscle protein into AA
  • Recovery phase: Anabolism>catabolism. Nutritional support provides substrate for anabolic state

Dose

• Mainly observational evidence and clinical experience
• Adjustments can be made based upon an estimate of individuals’s Resting Energy Expenditure (REE) or their body weight
• Adjustment based on body weight, variations based on age, using equations or indirect calorimetry
• Indirect calorimetry
  • better than REE equations
  • not routinely accessible, not adequately tested
• Predictive equations significant inaccuracy
• Dosing weight is hence routinely based on body weight / BMI with specific adjustments

Dosing weight

• Estimate current or pre-admission dry body weight
• Choose appropriate body weight based on BMI from which to calculate caloric and protein intake
  • Underweight (BMI <18.5 kg/m2): current weight as initial dosing weight. Ideal body weight could lead to excess initial calories and induce refeeding syndrome
  • Normal weight (BMI 18.5-24.9 kg/m2): current weight as dosing weight
  • Overweight (BMI 24.9-29.9 kg/m2): current weight as dosing weight
  • Obese (BMI >= 20 kg/m2): Adjusted body weight
• Ideal Body Weight (Devine formula):
  • IBW (men) = 50 kg + 2.3 kg x (height, in – 60)
  • IBW (women) = 45.5 kg + 2.3 kg x  (height, in – 60)
• Adjusted Body Weight
  • AdjBW = IBW + (0.4 * [Actual weight – IBW])
    • or AdjBW = 1.1 x IBW

DAILY NUTRITIONAL REQUIREMENTS

BUT these vary according to:

• Physiological factors:
  • Age, gender, body size
  • Pregnancy
  • Activity level
  • Hydration status
• Pathological factors
  • Burns and sepsis → ↑ protein and caloric intake
  • Renal failure → ↓ volume, protein and electrolyte (esp K+) content
  • CCF → fluid reduction
  • Hepatic failure → ↓ a.a/protein content to prevent encephalopathy
  • Respiratory failure → ↓ glucose to minimise CO2 production

• Calories
  • Fewer calories in the first week of critical illness: approx 8-10 kcal/kg/day
  • 25-30 kcal/kg/day in stable patient
  • upto 35 kcal/kg/day if weight gain is desired in stable patient and in a lower inflammatory state
  • 25kcal/kg/day or less if extubation is imminent
• Protein
  • Mild-mod Critical illness: 0.8-1.2 g/kg/day
  • Severe Critical Illness: 1.2-1.5kg/day
  • Severe burns: upto 2g/kg/day

Composition

FORMULATIONS:

• Common differences between formulas include osmolarity, caloric density, and amount of protein per calorie, as well as electrolyte, vitamin, and mineral content.
• Most are formulated to provide 100 percent of recommended daily vitamin and mineral dose when a minimum of approximately 1000 or more kilocalories are delivered per day.

STANDARD

• Isotonic to serum
• Caloric density of approximately 1 kcal/mL
• Lactose-free
• Intact (nonhydrolyzed) protein content of about 40 g/1000 mL (40 g/1000 kcal)
• Nonprotein calorie to nitrogen ratio of approximately 130
• Mixture of simple and complex carbohydrates
• Long-chain fatty acids (although some are now including medium-chain and omega-3 fats)
• Essential vitamins, minerals, and micronutrients (usually RDA provided in ~ 1000ml of feed)

OTHERS

• CONCENTRATED
  • useful in fluid restriction
  • mildly hyperosmolar
  • caloric density of 1.2,1.5 or 2.0 kcal/ml
  • no mortality or morbidity benefit
• PREDIGESTED
  • protein hydrolyzed to short-chain peptides, less complex carbohydrates
  • reduced total fat, increased MCT or altered TGs
  • weakly supported by data
  • Potential benefit in: Thoracic duct leak/chylothorax, digestive defects/malabsorbtion syndromes, failure to tolerate standard EN
  • Caloric density of 1 or 1.5 kcal/ml

COMPOSITION

• CARBOHYDRATE/FAT
  • Standard 49-53% / 29-30%
  • Other (not recommended for routine EN):
  • Low carb/high fat 28-40%/40-55%
  • high carb/low fat 85%/15%
• PROTEIN
  • High protein EN (1.2-2g/kg/day) – improved mortality
  • Acute/chronic renal disease: Low-protein EN not recommended for routine use. Renal formulas only if difficult to manage volume and electrolytes
  • Standard feeds for patients on CRRT
• Peptides – unlikely to be beneficial
• Omega-3 fatty acids and antioxidants, glutamine, probiotics/prebiotics – unlikely to be beneficial, and may be harmful
• Fiber
  • no benefit in diarrhoea prevention.
  • Mixed fibre feeds may help in persistent diarrhoea
  • avoid in pressors/ reduced mobility due to bezoars
• Vitamins and trace elements
  • included in feed upto RDA amounts
  • Routine supplementation usually not necessary. Definitely donot provide more than RDA

Side Effects