What is the difference between PN and EN? A Guide to Parenteral vs. Enteral Nutrition

Medical providers often prefer enteral nutrition over parenteral nutrition due to its lower cost, fewer complications, and more physiological route of administration. Understanding what is the difference between PN and EN is crucial for grasping how patients receive essential nutrients when they cannot eat normally.

Quick Summary

Enteral nutrition uses the gastrointestinal tract for feeding via mouth, oral supplements, or tubes, while parenteral nutrition bypasses it entirely, delivering nutrients directly into the bloodstream through a vein.

Key Points

• Route of Administration: EN uses the GI tract (oral or tube), while PN bypasses it completely, delivering nutrients directly into the bloodstream.

• Preference: EN is the preferred feeding method when the GI tract is functioning because it is safer, more natural, and less costly.

• Indications: PN is reserved for patients whose digestive system is non-functional or severely compromised, such as with severe malabsorption or bowel obstruction.

• Complication Risks: PN carries a higher risk of complications, including bloodstream infections and metabolic disturbances like hyperglycemia, compared to EN.

• Gut Health: Enteral feeding actively preserves the health and function of the gut mucosa, which is beneficial for overall immunity and recovery.

• Cost and Complexity: EN is a simpler and less expensive process, whereas PN requires complex formulations, careful administration, and intensive monitoring.

The Fundamental Distinction: Route of Administration

The most straightforward way to define the difference between enteral nutrition (EN) and parenteral nutrition (PN) is by the route of nutrient administration. Enteral nutrition is a feeding method that utilizes the gastrointestinal (GI) tract in some capacity, even if the patient cannot eat or swallow normally. This can range from oral liquid supplements to tube feedings that deliver nutrients directly to the stomach or intestines. In contrast, parenteral nutrition completely bypasses the digestive system and administers nutrients intravenously (via a vein) directly into the bloodstream.

This fundamental difference in how nutrients are delivered to the body dictates the methods, risks, benefits, and applications of each type of nutritional support.

Enteral Nutrition (EN): Feeding the GI Tract

What is EN?

Enteral nutrition relies on the body's natural digestive and absorptive processes. It is the preferred method of artificial nutritional support whenever the gastrointestinal tract is functional, at least in part. The goal is to provide a comprehensive and balanced nutrient profile that can be digested and absorbed.

Types of Enteral Access

Tube feeding is a common form of enteral nutrition when oral intake is impossible or insufficient. The type of access chosen depends on the anticipated duration of feeding and the patient's specific needs:

• Nasoenteric tubes: For short-term feeding, a tube is passed through the nose and into the GI tract.
  • Nasogastric (NG) tube: Ends in the stomach.
  • Nasojejunal (NJ) tube: Ends in the jejunum (small intestine).
• Enterostomy tubes: For long-term feeding, a tube is surgically placed directly into the stomach or small intestine through the abdominal wall.
  • Percutaneous Endoscopic Gastrostomy (PEG) tube: Placed into the stomach.
  • Percutaneous Endoscopic Jejunostomy (PEJ) tube: Placed into the jejunum.

Advantages of EN

Enteral nutrition is widely preferred for several reasons:

• More physiological: It uses the body's natural processes, which helps maintain the structural and functional integrity of the gut.
• Lower risk of infection: Unlike the intravenous access required for PN, enteral feeding avoids the higher risk of bloodstream infections.
• Lower cost: EN is significantly less expensive than PN, both in terms of materials and complexity of preparation.
• Preserves gut integrity: It prevents disuse atrophy of the gastrointestinal tract, which helps maintain gut barrier function.

Disadvantages and Risks of EN

While generally safer, EN is not without potential complications:

• Gastrointestinal intolerance: Patients can experience symptoms like bloating, cramps, nausea, or diarrhea.
• Tube-related issues: This includes tube displacement, blockages, or local skin irritation at the insertion site.
• Aspiration pneumonia: A risk if feeding formulas enter the lungs, particularly with nasogastric tubes.

Parenteral Nutrition (PN): Bypassing the Gut

What is PN?

Parenteral nutrition is necessary when a patient's gastrointestinal tract is non-functional, inaccessible, or unable to absorb nutrients adequately. The solution, often called Total Parenteral Nutrition (TPN), contains a complete mix of carbohydrates, protein, fats, electrolytes, vitamins, and minerals.

Types of Parenteral Access

PN is delivered through an intravenous (IV) line, with the access point depending on the concentration of the solution and duration of therapy:

• Peripheral Parenteral Nutrition (PPN): Administered via a peripheral vein in the arm. It is used for short-term, temporary support because the solutions are less concentrated and less irritating to smaller veins.
• Central Parenteral Nutrition (CPN): Administered through a central venous catheter, which is placed in a large vein (like the subclavian or jugular) to handle more concentrated solutions. This is used for long-term or complete nutritional support.

Advantages of PN

Parenteral nutrition is a life-saving therapy when a patient's GI system fails:

• Bypasses the GI tract: It provides nutritional support to patients with conditions like bowel obstruction, short bowel syndrome, or severe malabsorption.
• Precisely tailored: The nutrient solution can be meticulously formulated to meet specific and complex patient requirements.

Disadvantages and Risks of PN

Parenteral nutrition is more invasive and carries greater risks than EN:

• High risk of infection: Central venous catheters are a primary source of bloodstream infections.
• Metabolic complications: Managing glucose levels and other metabolic factors is complex and requires careful monitoring. Hyperglycemia is a common risk.
• Organ complications: Long-term PN can lead to liver or bone disease.
• Higher cost: The therapy is more complex and expensive to administer.

Comparison Table: What is the difference between PN and EN?

Feature	Enteral Nutrition (EN)	Parenteral Nutrition (PN)
Route	Uses the gastrointestinal (GI) tract	Bypasses the GI tract; delivered intravenously
Indication	Functional or partially functional GI tract	Non-functional or inaccessible GI tract
Cost	Less expensive	More expensive
Risks	Lower risk of infection, aspiration, GI intolerance	Higher risk of infection (sepsis), metabolic issues
Physiology	More physiological, supports gut integrity	Less physiological, can cause gut atrophy
Duration	Can be used long-term	Can be long-term, but often used temporarily
Administration	Oral supplements, nasoenteric or enterostomy tubes	Central venous or peripheral intravenous line
Monitoring	Less intensive metabolic monitoring required	Requires intensive monitoring of glucose and electrolytes

How the Choice is Made

The decision between EN and PN is a critical medical judgment made by a healthcare team. The primary principle is to use the gut if it works. Therefore, if the GI tract is functioning, EN is almost always the first and preferred option due to its safety, cost-effectiveness, and physiological benefits. PN is reserved for patients where EN is contraindicated or not meeting the nutritional needs adequately. In some cases, both EN and PN may be used simultaneously to supplement each other. The ultimate goal is always to provide the patient with the most appropriate and effective nutritional support for their specific clinical situation.

Conclusion

To summarize, the core distinction between PN and EN lies in their delivery method: PN uses the bloodstream, while EN uses the digestive system. EN is the safer, more natural, and less expensive option when the gut is operational, preserving gut health and reducing complication risks. PN is a crucial, life-sustaining therapy for those with compromised GI function but is more invasive and carries higher infectious and metabolic risks. The choice between them is a deliberate medical decision, emphasizing EN as the first line of defense whenever possible to provide optimal patient care. For further information on the specific procedures and guidelines for nutritional support, resources such as the American College of Gastroenterology can be helpful.

Frequently Asked Questions

When is PN used instead of EN?

PN is used when the patient cannot tolerate or use their gastrointestinal tract for nutrition, such as with bowel obstruction, severe pancreatitis, short bowel syndrome, or other severe GI disorders.

Which feeding method is safer, EN or PN?

Enteral nutrition (EN) is generally considered safer than parenteral nutrition (PN) because it has a lower risk of serious infections, especially bloodstream infections associated with intravenous catheters.

Can a patient be on both EN and PN at the same time?

Yes, in some clinical scenarios, a patient may receive a combination of both enteral and parenteral nutrition. This is often done when EN is not providing sufficient calories and nutrients to meet the patient's full needs.

What is Total Parenteral Nutrition (TPN)?

Total Parenteral Nutrition (TPN) is a specific type of PN that provides all of a patient's nutritional requirements, including carbohydrates, proteins, fats, vitamins, and minerals, via an IV line.

Is enteral nutrition always tube feeding?

No, while tube feeding is a common form of enteral nutrition, the term technically also includes oral nutritional supplements. In clinical practice, however, 'enteral nutrition' often refers strictly to tube feeding.

What are the common risks of PN?

The risks of PN include hyperglycemia (high blood sugar), catheter-related bloodstream infections, electrolyte imbalances, and long-term complications affecting the liver and bones.

How long can a patient be on EN vs. PN?

EN can be used for both short-term and long-term nutrition, depending on the patient's condition and the type of feeding tube used. PN is often used short-term, but it can be necessary long-term or even permanently in some chronic conditions where the GI tract is non-functional.