Total Parenteral Nutrition

Introduction

Total Parenteral Nutrition (TPN) is a method of providing complete nutritional support to patients who cannot be fed sufficiently either orally or enterally, as recommended by the European Society for Clinical Nutrition and Metabolism and the American Society for Parenteral and Enteral Nutrition 1, 2
TPN is indicated in cases of intestinal failure, such as short bowel syndrome, and when the enteral route is contraindicated due to conditions such as intestinal obstructions or ileus, severe shock, intestinal ischemia, high output fistula, and severe intestinal hemorrhage, according to the American Gastroenterological Association and the American Society for Parenteral and Enteral Nutrition 3, 4

TPN contains amino acids, glucose, lipids, electrolytes, vitamins, and trace elements, with carbohydrates providing 3.4 kcal/mL and a maximum infusion rate of 5-7 mg/kg/min, and blood glucose should be maintained at 180-200 mg/dL 4
Proteins are provided as free amino acids, with a dosage of 1.0-1.5 g/kg/day based on ideal body weight for adults, and lipids typically provide 20-30% of total calories, with a 20% lipid emulsion being more calorically dense than dextrose, and serum triglyceride levels should be kept below 400-800 mg/dL 4
Vitamins, including water-soluble and fat-soluble vitamins, have specific dosing recommendations, such as Vitamin A: 10,000-50,000 units daily, Vitamin B12: 300 μg subcutaneously monthly, and Vitamin C: 200-500 mg 4

Energy requirements are 25-30 kcal/kg/day based on ideal body weight, and electrolytes, including sodium, potassium, calcium, magnesium, phosphate, and chloride, require individualized dosing based on serum levels 4

Infants and children require higher levels of support per kg of body weight, and patients with glucose intolerance may require higher percentage of lipid calories, while patients with renal or hepatic dysfunction require modified formulations 4
Patients with cardiac or renal dysfunction require more cautious fluid administration, and patients with high stomal output may need more frequent fluid boluses in addition to TPN 5
Severely malnourished patients are at risk of refeeding syndrome with rapid fluid shifts 6

TPN requires careful monitoring, including blood glucose levels, electrolyte balance, fluid status, and phosphate, potassium, and magnesium levels, especially when refeeding malnourished patients, according to the European Society for Clinical Nutrition and Metabolism 1
TPN should be administered with accurate flow control via continuous infusion or cyclic administration rather than bolus delivery, as recommended by Clinical Nutrition guidelines 7
Continuous infusion is a traditional method for hospitalized patients, providing stable nutrient delivery over 24 hours, and is recommended for acutely ill patients until metabolically stable, while cyclic infusion is preferred for long-term or home TPN, administered over a shorter period, typically 10-12 hours, and usually given overnight with gradual tapering 7

Incompatibility issues, fluid overload, line contamination, and disrupting TPN schedule are potential complications that can be avoided by following guidelines and maintaining strict aseptic technique when accessing any line in a TPN patient 5
TPN must be administered with accurate flow control via infusion pumps, and the infusion system should be under regular visual inspection, with terminal filters used, including lipid emulsions through 1.2-1.5 μm filters and aqueous solutions through 0.22 μm filters, as recommended by Clinical Nutrition guidelines 7

Home Parenteral Nutrition (HPN) is used for patients with chronic intestinal failure or malignant obstruction or partial obstruction of the gastrointestinal tract, as stated by the American Society for Parenteral and Enteral Nutrition 2
Patients on HPN require careful monitoring and management of their nutritional and fluid needs, with regular follow-up appointments and adjustments to their TPN regimen as needed 5