Nutritional support of a critically ill child

Nutritional support is a fundamental component of pediatric critical care. Critical illness induces a hypermetabolic and hypercatabolic stress response that differs significantly from simple starvation.

• Physiological Response to Stress:
  • Hypermetabolism: Energy expenditure may increase to 120–250% of normal in conditions like head injury or sepsis.
  • Hypercatabolism: There is increased urinary nitrogen excretion and muscle breakdown to provide amino acids for gluconeogenesis and acute-phase protein synthesis.
  • Hormonal Changes: High levels of catabolic hormones (cortisol, catecholamines) and insulin resistance lead to hyperglycemia.
• Starvation vs. Stress:
  • In simple starvation (e.g., marasmus), the body adapts by "reductive adaptation," lowering the Basal Metabolic Rate (BMR) and conserving energy ("hibernation" effect).
  • In critical illness (trauma, sepsis), the body cannot economize energy; metabolic demands remain high despite lack of intake.
• Goals of Support:
  • Prevent further loss of lean body mass (autocannibalism).
  • Support immune function and wound healing.
  • Prevent specific nutrient deficiencies.
  • Restore normal body composition during convalescence.

Assessment of Nutritional Requirements

Estimating requirements in the critically ill child is complex due to the interplay of baseline needs, stress factors, and organ dysfunction.

Energy Requirements

• Basal Metabolic Rate (BMR): Roughly 50% of total energy expenditure in a normal child.
• Impact of Illness:
  • Fever: For every 1°C rise in temperature, caloric requirement increases by 10-12%.
  • Reduced Activity: In a bedridden child, energy needs for activity and growth are reduced. Often, providing 2/3rds of the standard Recommended Dietary Allowance (RDA) is sufficient initially.
  • Mechanical Ventilation: Sedation and ventilation decrease the work of breathing, potentially lowering energy expenditure.
• Calculation Methods:

  • Holliday and Segar Formula: Used for maintenance calorie and fluid estimation based on weight.

    • 0–10 kg: 100 kcal/kg.
    • 10–20 kg: 1000 kcal + 50 kcal/kg for every kg >10.

    • 20 kg: 1500 kcal + 20 kcal/kg for every kg >20.

  • Therapeutic Calculation: In hospital settings, 150–200 kcal/kg (based on observed weight) is often targeted for malnutrition recovery.

Fluid Requirements

• Maintenance: Generally follows the Holliday and Segar formula (1 mL fluid per 1 kcal of energy).

  • 1st 10 kg: 100 mL/kg.
  • 11–20 kg: 1000 mL + 50 mL/kg for each kg >10.

  • 20 kg: 1500 mL + 20 mL/kg for each kg >20.

• Restriction: Fluid restriction to 2/3rds of maintenance is indicated in conditions prone to Syndrome of Inappropriate ADH (SIADH), such as meningitis, pneumonia, and head injury.

• Oligo-anuria: Fluid should be restricted to insensible losses (approx. 400 mL/m²/day or 30 mL/kg for infants) plus the volume of the previous day's urine output.

Macronutrient Requirements

• Proteins:
  • Standard requirement: 1.5–2 g/kg/day.
  • Hypercatabolic states/Malnutrition: May require up to 3–4 g/kg/day.
  • Renal Failure: Restrict to 0.25–0.5 g/kg/day to prevent azotemia.
• Carbohydrates:
  • Should provide 50–60% of total calories.
  • Glucose infusion rates of 6–12 mg/kg/min are typically tolerated; higher rates may cause fatty liver.
• Fats:
  • Provide 25–45% of calories.
  • MCT (Medium Chain Triglycerides): Useful in hepatobiliary disease, pancreatitis, and fat malabsorption because they are absorbed directly into the portal vein and do not require bile salts.
  • Coconut oil is a practical source of MCT.

Micronutrients

• Requirements for vitamins and minerals (e.g., Zinc, Iron, B-complex) increase 5–10 times during illness due to excessive losses and increased metabolic demand.

Fluid Resuscitation in Shock

Management of shock is the first priority in a critically ill child. Protocols differ based on nutritional status.

Child without Severe Acute Malnutrition (SAM)

• Signs: Cold extremities, capillary refill time (CRT) >3 seconds, weak/fast pulse.
• Management:
  • Fluid Bolus: 20 mL/kg of Normal Saline (NS) or Ringer's Lactate (RL) as rapidly as possible.
  • Reassessment: If no improvement, repeat bolus (up to 3 times total 60 mL/kg).
  • Refractory Shock: If shock persists after fluid resuscitation, initiate inotropes (Dopamine or Epinephrine).
  • Hemorrhagic Shock: If blood loss is suspected, give 20 mL/kg blood transfusion.

Child with Severe Acute Malnutrition (SAM)

• Risk: These children have a "frail" heart and are at high risk of fluid overload and heart failure with standard resuscitation protocols.
• Shock Definition in SAM: Lethargic/unconscious AND cold hands plus slow CRT (>3 sec) or weak fast pulse.
• Modified Protocol:
  • Pre-treatment: Give 10% Glucose (5 mL/kg) IV to prevent hypoglycemia.
  • Fluid: Use Half-Normal Saline (0.45% NaCl) with 5% Dextrose or Ringer's Lactate with 5% Dextrose.
  • Rate: 15 mL/kg over 1 hour (much slower than non-SAM children).
  • Monitoring: Pulse and respiratory rate every 5–10 minutes. If they increase (HR by 15, RR by 5), stop infusion immediately to prevent heart failure.
  • Subsequent Steps: If improved after 1st hour, repeat 15 mL/kg over next hour, then switch to oral/NG rehydration (ReSoMal). If no improvement, assume septic shock and start maintenance fluids and inotropes.

Enteral Nutrition (EN)

Enteral nutrition is preferred over parenteral nutrition because it preserves gut mucosal integrity, is more physiological, safer, and less expensive.

Principles

• Early Initiation: Start as soon as the patient is hemodynamically stable. Even "minimal enteral feeding" (trophic feeding) prevents mucosal atrophy caused by TPN.
• Routes:
  • Oral: Best route if tolerated.
  • Nasogastric (NG): For comatose, preterm, or anorectic patients.
  • Continuous vs. Bolus: Continuous drip feeding is preferred in critically ill patients to prevent vomiting, aspiration, and abdominal distension, as it does not induce forceful peristalsis.

Diet Formulations

• Standard/Polymeric: Whole protein, suitable for most (e.g., milk, family pot).
• Isodense Formulas: Supply 100 kcal/100 mL (1 kcal/mL). Can be prepared by adding sugar and oil to milk.
  • High Energy Milk: 100 mL milk + 1 tsp sugar + 1/2 tsp oil.
  • Cereal-Pulse Mix: Precooked mixes (e.g., SAT mix) can be dissolved to provide calorie-dense feeds.
• Therapeutic Diets:
  • Lactose-Free: For persistent diarrhea/secondary lactose intolerance (e.g., chicken-based, soya-based).
  • Elemental/Semi-elemental: Pre-digested proteins (amino acids/peptides) and MCTs for short bowel syndrome or severe malabsorption.

Complications of EN

• Gastrointestinal: Diarrhea (often due to hyperosmolar feeds or hypoalbuminemia), vomiting, distension.
• Mechanical: Tube displacement, blockage, aspiration pneumonia.
• Metabolic: Hyperglycemia, electrolyte imbalance, refeeding syndrome.

Parenteral Nutrition (PN)

PN is indicated when the gut cannot be used (e.g., intestinal obstruction, perforation, severe NEC) or when enteral intake is insufficient.

Partial Parenteral Nutrition (PPN)

• Route: Peripheral vein.
• Limitation: Osmolarity must be limited to prevent thrombophlebitis. Glucose concentration should generally not exceed 12.5%.
• Role: Supplement to enteral feeds.

Total Parenteral Nutrition (TPN)

• Route: Central venous access (Subclavian, Jugular, or PICC) required for hypertonic solutions.
• Composition Guidelines:
  • Fluids: 100–150 mL/kg/day.
  • Glucose: 15–30 g/kg/day. Start at 6 mg/kg/min and increase slowly.
  • Proteins: Crystalline amino acids (e.g., Aminosyn, Vamin). Dose: 2–3 g/kg/day.
  • Lipids: 20% Intralipid (soybean/safflower oil). Essential to prevent Essential Fatty Acid deficiency. Dose: 1–3 g/kg/day.
  • Additives: Multivitamins (MVI Pediatric), trace elements (Zinc, Copper, Selenium), Calcium, Phosphorus, Magnesium, Heparin (to prevent thrombophlebitis).
• Monitoring: Strict asepsis is vital. Monitor blood glucose, electrolytes, liver function (cholestasis is a risk), and triglycerides.

Nutritional Management in Specific Conditions

1. Severe Acute Malnutrition (SAM)

• Stabilization Phase (Day 1-7):
  • Hypoglycemia: Treat glucose <54 mg/dL immediately with 10% Dextrose (5 mL/kg IV or 50 mL oral).
  • Hypothermia: Rewarm if temp <35.5°C; feed frequently.
  • Dehydration: Use ReSoMal (Rehydration Solution for Malnutrition) or low-osmolarity ORS with added potassium. Do not use standard IV fluids for dehydration unless shock is present. Oral rehydration rate is slow: 5 mL/kg every 30 mins for 2 hours, then 5-10 mL/kg alternate hours.
  • Electrolytes: Supplement Potassium (3-4 mEq/kg) and Magnesium. Restrict Sodium.
  • Diet: Start F-75 (75 kcal/100 mL, 0.9g protein/100 mL). Feed small amounts every 2 hours. Do not give high protein/iron in this phase.
• Rehabilitation Phase (Week 2-6):
  • Transition to F-100 (100 kcal/100 mL, 2.9g protein/100 mL) or Ready-to-Use Therapeutic Food (RUTF).
  • Goal: Catch-up growth (>10 g/kg/day).
  • Add Iron supplementation now.

2. Acute Renal Failure (ARF)

• Fluid: Restrict to Insensible Water Loss (IWL) + Urine Output.
  • IWL: ~400 mL/m²/day or 30 mL/kg (infants) to 10 mL/kg (adults).
• Protein: Restrict to 0.5–1.25 g/kg/day to minimize azotemia.
• Electrolytes: Restrict Sodium and Potassium. Monitor for hyperkalemia.
• Calories: Provide adequate non-protein calories (fats/carbs) to prevent endogenous protein catabolism.

3. Hepatic Failure

• Protein: In hepatic encephalopathy, standard proteins may need restriction. Branched Chain Amino Acids (BCAA - Valine, Leucine, Isoleucine) are preferred as they are metabolized in muscle, unlike aromatic amino acids which require the liver.
• Fat: Use MCTs if bile flow is obstructed.
• Carbohydrate: Prevent hypoglycemia (a common complication).

4. Respiratory Failure

• Energy: Hypermetabolic state due to increased work of breathing.
• Carbohydrate Load: Excess carbohydrate metabolism produces CO2 (high Respiratory Quotient), increasing the ventilatory burden. A high-fat diet may be beneficial to lower CO2 production in ventilator-dependent children.

5. Congenital Heart Disease (CCF)

• Growth Failure: Common due to cardiac cachexia and anorexia.
• Restriction: Fluids and Sodium (1-2 g/day) must be restricted to manage load.
• Density: Feeds must be calorie-dense (hypercaloric formulas) to provide adequate energy in a restricted volume.

Summary of Feeding Protocol for a Critically Ill Child

1. Stabilize: Secure Airway, Breathing, Circulation. Correct Hypoglycemia/Electrolytes.
2. Calculate: Fluid needs (maintenance vs. restriction) and Caloric needs (BMR + stress factor).
3. Choose Route: Oral > NG > Peripheral Parenteral > Central Parenteral.
4. Select Feed: Age-appropriate, isodense (1 kcal/mL) if fluid restricted, specialized for organ failure.
5. Monitor: Weight, hydration status, abdominal girth, residuals, and biochemistry daily.