What is Total Parenteral Nutrition?
Total parenteral nutrition (TPN) is a method of feeding a person intravenously. TPN provides nutrition through a central vein, bypassing the usual process of eating and digestion. TPN is used when a person's gastrointestinal tract is non-functioning because of an impairment or disease. TPN provides hydration and essential nutrients like proteins, carbohydrates, fats, vitamins, minerals and electrolytes directly into the bloodstream.
Why is Total Parenteral Nutrition Used?
There are several medical conditions that may require TPN when a person is unable to eat or digest food normally. Some common reasons TPN is used include:
- Short bowel syndrome due to surgery or disease
- Gastrointestinal disorders like Crohn’s disease, ulcerative colitis, gastroparesis, intestinal pseudo-obstruction
- Intestinal blockage or narrowing due to scar tissue, hernia or cancer
- Severe pancreatitis when eating cannot be tolerated
- High-output fistulas in the GI tract
- Cancer in the head, neck or esophagus
- Serious burns requiring increased nutrition
- Malnutrition from anorexia nervosa
- AIDS patients with severe wasting
TPN allows nutrition and hydration to be maintained when the GI tract is not functioning. It improves wound healing, maintains or increases weight, and supports the immune system until normal eating can resume.
What are the Components of TPN?
The TPN solution contains a customized blend of vital nutrients tailored to each patient’s needs. The main components include:
- Amino acids - Building blocks of protein
- Dextrose - Source of carbohydrate calories
- Lipids - Essential fatty acids
- Electrolytes - Sodium, potassium, calcium, magnesium, etc.
- Vitamins and minerals - Thiamine, folate, zinc, iron, etc.
- Trace elements - Copper, manganese, chromium, etc.
- Water - For hydration and diluting additives
The solution is prepared under sterile conditions and dispensed into IV bags. The nutrient balance can be adjusted based on lab tests and clinical status.
Total Parenteral Nutrition Images
TPN solution in an intravenous bag ready for infusion.
A patient receiving TPN solution through an IV line.
An electronic TPN pump controls the infusion rate.
How is Total Parenteral Nutrition Administered?
Patients receiving TPN require careful monitoring under the supervision of healthcare providers. TPN is administered as follows:
Venous Access
A large central vein is catheterized to administer TPN. Common insertion sites are the subclavian vein near the collarbone, internal jugular vein in the neck, or femoral vein in the groin. A peripherally inserted central catheter (PICC line) may also be used. The tip of the catheter is advanced to the superior vena cava or right atrium.
Infusion
The TPN solution flows from an IV bag through tubing into the central catheter. An electronic infusion pump controls the flow rate and delivers the prescribed amount of nutrients continuously over 24 hours. Some TPN regimens involve infusions over 12-16 hours rather than 24.
Care and Maintenance
The IV tubing is changed every 24 hours when new TPN bags are connected. The central line dressing is kept clean and dry to prevent infection. Lab tests help determine correct electrolyte and nutrient levels. The solution may be adjusted daily based on test results and patient response.
Benefits of Total Parenteral Nutrition
When oral or tube feeding is not possible, TPN can be life-saving. Benefits include:
- Prevents malnutrition, starvation and severe weight loss
- Supplies hydration when unable to drink fluids
- Allows GI tract to rest and heal when not functioning
- Provides energy and supports immune function
- Avoids need for additional surgery to place feeding tube
- Customizable to meet individual nutrition needs
- Improves wound healing after surgery or injury
- Supports muscle and nerve function
- May facilitate weaning off ventilator in ICU patients
Downsides and Risks of TPN
While TPN can improve health in the short-term, there may be adverse effects with prolonged use:
- Infection - Central line poses risk of bloodstream infections
- Blood clots - Thrombosis may develop with central catheters
- Liver problems - TPN can lead to fat accumulation and damage in liver
- Metabolic complications - Fluctuating blood sugar levels, mineral imbalances
- Loss of gut barrier function and immunity - Intestinal villi atrophy
- Central line complications - Pneumothorax, hemothorax, arterial puncture
- Micronutrient deficiencies - Vitamin loss from light exposure
Patients on TPN require close monitoring to minimize risks. Healthcare providers try to transition patients back to an oral or enteral diet as soon as tolerated.
Weaning off Total Parenteral Nutrition
The goal is to wean patients off TPN and back to a normal diet as their clinical condition improves. This requires carefully reintroducing oral or tube feeding:
Clear Liquid Diet
If the gut is functional, small trial feedings of clear liquids (water, juice, broth, popsicles) may be started. Electrolytes and glucose are monitored to ensure stability.
Full Liquid Diet
If clear liquids are tolerated, advance to a full liquid diet with nutritional supplements, milk, yogurt, pureed foods. The TPN infusion is decreased accordingly.
Soft Solid Foods
With tolerance of liquids, soft bland foods (applesauce, mashed potatoes, yogurt, oatmeal, soup) are tried next. More calories are shifted from TPN to the GI tract.
Regular Diet
The final step is returning to a regular healthy diet as digestive function normalizes. TPN is discontinued once adequate oral/enteral intake is achieved.
This gradual progression allows the GI tract to adjust and avoids refeeding syndrome risks.
Long-Term Outcomes on Total Parenteral Nutrition
Some patients with chronic intestinal failure or short bowel syndrome may require TPN for months or years. Potential long-term implications include:
- Repeated infections and sepsis from central lines
- Progressive liver disease if unable to wean off TPN
- Metabolic bone disease and osteoporosis
- Formation of gallstones or kidney stones
- Micronutrient deficiencies if not adequately supplemented
- Changes in gut microbiome
- Central line-associated blood clots
- Psychological impact of prolonged dependence
Careful nutritional monitoring and management can improve outcomes on long-term TPN. Some patients may eventually qualify for small bowel transplantation.
Summary
Total parenteral nutrition is a life-saving intervention for patients unable to get nutrition enterally due to intestinal failure. TPN provides intravenous infusion of hydration and essential nutrients like proteins, carbs, fats, electrolytes and vitamins. Patients require careful monitoring to avoid risks like infection and liver disease. The goal is to transition back to oral/enteral feeding as soon as feasible and discontinue TPN. Some patients may remain TPN-dependent long-term if intestinal function cannot be restored.
FAQs
What are the main components of TPN?
The main components of TPN solution include amino acids (protein), dextrose (carbs), lipids (fats), electrolytes, vitamins, minerals, trace elements and water.
How is TPN administered?
TPN requires insertion of a central venous catheter into a large vein like the subclavian, jugular or femoral. The TPN solution flows from an IV bag through the catheter using an electronic infusion pump to control the rate.
What kind of nutrition should patients start with when weaning off TPN?
Patients should start with clear liquids, advance to full liquids, then soft solid foods, before returning to a regular diet as tolerated when transitioning off TPN.
What are the risks associated with long-term TPN use?
Risks of prolonged TPN use include central line infections, liver disease, metabolic bone disease, gallstones, kidney stones, blood clots, and micronutrient deficiencies.
Why is special venous access needed for TPN infusions?
TPN solutions must be administered through a central venous catheter into a large vein like the subclavian or jugular. Peripheral IVs cannot be used due to the hypertonic nature of the TPN solution.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.
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