What is Total Parenteral Nutrition (TPN)?

From the Guidelines

Total parenteral nutrition (TPN) should be considered for patients with non-functioning gastrointestinal tracts, severe malabsorption, bowel obstruction, or those requiring bowel rest for extended periods, with careful monitoring for complications and individualized formulation based on patient needs, as recommended by the most recent guidelines 1.

Indications and Formulation

TPN delivers all essential nutrients, including proteins, carbohydrates, fats, vitamins, minerals, and electrolytes, through an intravenous catheter. A standard adult TPN formulation might include:

• 1-2 g/kg/day of protein
• 20-35 kcal/kg/day of total calories
• 20-30% of calories from lipids and the remainder from dextrose
• Electrolytes, vitamins, and trace elements added based on individual needs, with specific recommendations including:

• Vitamin A: 10,000–50,000 units daily
• Vitamin B12: 300 µg subcutaneously monthly for those with terminal ileal resections or disease
• Vitamin C: 200–500 mg
• Vitamin D: 1600 units DHT daily; may require 25-OH-or 1,23 (OH)-D3
• Vitamin E: 30 IU daily
• Vitamin K: 10 mg weekly
• Calcium and magnesium: tailored to individual patient needs
• Iron, selenium, and zinc: as needed, with specific recommendations including 60–100 µg daily of selenium and 220–440 mg daily of zinc (sulfate form)

Monitoring and Complications

TPN requires careful monitoring for complications, including:

• Infection
• Metabolic disturbances (hyperglycemia, electrolyte imbalances)
• Liver dysfunction
• Catheter-related issues Regular blood tests to check metabolic parameters and nutrition status are essential. TPN should be initiated gradually and discontinued slowly to avoid refeeding syndrome or hypoglycemia.

Clinical Scenarios

The use of home parenteral nutrition (HPN) can be identified in four clinical scenarios, based on underlying gastrointestinal function and disease, in tandem with patient characteristics, as outlined in the ESPEN practical guideline 1. While life-saving in appropriate circumstances, TPN bypasses the gut's important immune and barrier functions, so enteral nutrition (feeding through the digestive tract) is preferred whenever possible.

From the Research

Total Parenteral Nutrition Overview

• Total parenteral nutrition (TPN) is a life-saving intervention for patients where oral or enteral nutrition cannot be achieved or is not acceptable 2.
• The essential components of TPN are carbohydrates, lipids, amino acids, vitamins, trace elements, electrolytes, and water 2.
• TPN should be provided via a central line because of its hypertonicity, but peripheral PN can be administered via a non-central line with lower nutrient content and larger volume 2.

Indications for Total Parenteral Nutrition

• Indications for TPN include intestinal fistulas, severe short bowel syndrome, unresolving pancreatitis, advanced inflammatory bowel disease, delayed postoperative gastrointestinal function, developmental anomalies of the intestinal tract, protracted diarrhea of infancy, and hypermetabolic states 3.
• TPN can be used for malnourished patients or high-risk patients with malnutrition where the feasibility of full enteral nutrition is in question 2.

Complications of Total Parenteral Nutrition

• Complications encountered in patients receiving TPN include catheter-related mechanical problems, infections, and metabolic abnormalities 3.
• Metabolic complications related to macro and micronutrient disturbances, such as hyperglycemia, hypertriglyceridemia, and electrolyte imbalance, may occur at any time during TPN therapy 2.
• Long-term complications, such as hepatobiliary and bone disease, are associated with longer TPN therapy and home-TPN 2.

Formulations of Total Parenteral Nutrition

• Initial formulations of TPN consisted of carbohydrates, amino acids, vitamins, trace minerals, electrolytes, and water 4.
• A stable intravenous fat emulsion permitted the combination of all 3 macronutrients in the same admixture (3-in-1 or total nutrient admixture [TNA]) 4.
• The 3-in-1 formulation is considered safe and can be used as the standard of care in adult TPN 4, 5.

Administration of Total Parenteral Nutrition

• TPN can be administered via a central line or a non-central line with lower nutrient content and larger volume 2.
• The use of total nutrient admixture (TNA) offers convenience of administration and potential cost savings to the healthcare institution 5.
• However, the TNA is not without concerns, including compromised formulation at low macronutrient concentrations and increased risk of catheter occlusion 5.