What is the composition and administration of Total Parenteral Nutrition (TPN)?

Total Parenteral Nutrition: Composition and Administration

Total parenteral nutrition (TPN) is a type of nutrition therapy provided through intravenous administration of nutrients including amino acids, glucose, lipids, electrolytes, vitamins, and trace elements when a patient's complete nutritional needs must be met exclusively through the intravenous route. 1

Composition of TPN

Macronutrients

• Amino acids/Protein:

  • Standard requirement: 0.8-1.0 g/kg/day for unstressed adult patients 1
  • Provided as synthetic amino acid solutions

• Carbohydrates:

  • Provided as glucose/dextrose
  • Should not exceed 7 mg/kg/minute to prevent metabolic complications 1
  • Typically contributes 60-70% of non-protein calories

• Lipids:

  • For long-term TPN (>6 months), should not exceed 1 g/kg/day 1
  • Essential fatty acid requirement: 7-10 g/day 1
  • Sources include:
    • LCT fat from soya oil (14-20 g provides essential fatty acids)
    • LCT fat from olive/soya oil (30-40 g provides essential fatty acids)
    • MCT/LCT and fish oil emulsions are also safe and effective 1
  • Should contribute 30-40% of non-protein calories

• Total energy:

  • 20-35 kcal/kg/day 1
  • Non-protein energy should be 100-150 kcal for every gram of nitrogen 1

Micronutrients

• Electrolytes: Composition should reflect fluid losses 1

  • Sodium, potassium, calcium, magnesium, phosphate, chloride

• Vitamins: Fat-soluble (A, D, E, K) and water-soluble (B complex, C)

• Trace elements: Zinc, copper, selenium, manganese, chromium, iron

Administration of TPN

Access Devices

• Central venous access: Required for TPN due to high osmolarity
  • Tunneled central catheters for long-term use 1
  • Implanted ports are an acceptable alternative 1
  • PICC lines are not recommended for long-term HPN 1

Administration Methods

• Cyclic administration: Recommended over continuous infusion 1

  • Typically infused over 12-16 hours, allowing catheter rest periods
  • Helps reduce risk of metabolic complications and liver disease 1

• Infusion pumps: Recommended for accurate delivery 1

  • Essential for controlling infusion rate and preventing complications

Monitoring Requirements

• Regular biochemical monitoring:
  • Electrolytes, glucose, liver function tests, renal function
  • Trace elements and vitamins at 6-month intervals 1
  • Bone mineral density assessment yearly 1

Clinical Applications

Indications for TPN

• Primary indications:

  • Intestinal failure where oral/enteral nutrition is impossible 1
  • Severe short bowel syndrome
  • Intestinal fistulas
  • Prolonged ileus
  • Severe malabsorption

• Duration considerations:

  • Short-term: Hospital setting
  • Long-term: Home parenteral nutrition (HPN) for chronic intestinal failure 1

Complications and Management

Major Complications

• Catheter-related:

  • Infection (catheter-related bloodstream infections)
  • Thrombosis
  • Mechanical problems

• Metabolic:

  • Hyperglycemia
  • Electrolyte imbalances
  • Refeeding syndrome

• Hepatobiliary:

  • TPN-associated liver disease
  • Prevention: Maintain fat/glucose energy ratio ≤40:60 1
  • Avoid overfeeding 1
  • Control infections promptly 1

Special Considerations

• All-in-one admixtures: Preferred for reducing handling and contamination risks 2

• Drug compatibility: Generally, non-nutrient drugs should not be included in TPN admixtures due to safety concerns 2

• Home TPN: Requires comprehensive patient/caregiver training program 1

  • Catheter care
  • Pump use
  • Complication recognition and management

TPN is a complex therapy requiring expertise from a nutrition support team for optimal outcomes. When properly administered, it can be life-saving for patients with intestinal failure who cannot meet their nutritional needs through enteral routes.