Parenteral nutrition

Goals:

• Maintain lean body mass
• Provide energy for basal metabolism and activity
• Provide macro- and micro-nutrients for healing

Indications:

• Non-functioning or inaccessible GI tract
• High output fistula
• Postop ileus
• Insufficient enteral absorption e.g. short gut, IBD, dysmotility

Contraindications:

• Fasting < 5 days
• Ability to receive enteral feeding
• Terminal illness

Routes of access:

• CVL
• Peripheral venous access – short term only

Nutrient solutions

• Energy sources – 25-35 kCal/kg/day.
  • Dextrose (aka D-glucose) (~50%) ~3-4 g/kg/day
  • Fat as lipid emulsions (~30%) 1 g/kg/day
  • During critical illness, fat is the preferred source, and need to reduce feeds – overfeeding is dangerous. Metabolism is in acute phase and not ready to process nutrients.
• Nitrogen sources – solution of crystalline amino acids. Insoluble amino acids may be absent or present in inadequate amounts.
  • Protein (~20%) 0.8 – 1.5 g/kg/day to avoid lean tissue loss
• Water – 30-40 ml/kg/day
• Electrolytes (mmol/L): sodium 100 – 150, potassium 50 – 100, magnesium 8 – 24, calcium 10 – 20, phosphate 15 – 30.
• Trace elements and vitamins must be added daily. Vitamin K not included.

Complications of TPN:

• Metabolic disturbances:
  • Hyperglycaemia → lactic acidosis
  • Electrolyte disturbances
  • Refeeding syndrome
  • TPN associated liver dysfunction - https://doi.org/10.1002%2Fcld.888

Complications Associated with Parenteral nutrition

• Central line insertion and parenteral nutrition can lead to the following complications:

1. Pneumothorax
2. Major vein thrombosis
3. Thrombophlebitis
4. Sepsis and occasionally endocarditis
5. Arterial rather than venous cannulation
6. Eroded or misplaced catheter
7. Arrythmias
8. Abnormal LFTs and cholestasis

Managing TPN Line Sepsis

• If pt unstable and high index of suspicion, e.g. high fevers:
  • Remove the line
• If pt stable:
  • Take central and peripheral cultures
  • Start antibiotics
  • Start ethanol locks
  • Stop TPN – perfect culture medium
• If Staph aureus or Fungal:
  • Hard to clear
  • Will probably lose the line
• If replacing TPN line:
  • Consider antibiotic coated line
  • Start 70% ethanol locks twice weekly

TPN Cholestasis

• Big difference between early and late
• Early cholestasis:
  • Ubiquitous
  • Almost always due to reversible steatosis
  • Can be ignored most of the time
  • If concerned, can increase lipid content and reduce glucose or total caloric load
• Late cholestasis:
  • More severe and dangerous
• Management Options for Late Cholestasis:
  • Avoid sepsis
  • Cycling TPN to give body TPN-free hours during each day for liver to recover
  • Ursodeoxycholic acid
  • Metronidazole – if SIBO suspected