Parenteral feeding, more accurately termed parenteral nutrition (PN), is a method of providing liquid nutrition and hydration directly into a person's bloodstream. The term "parenteral" literally means "outside of the digestive tract". This feeding method is used for patients who cannot receive or absorb adequate nutrients via the normal enteral (digestive) route. A specialized team of healthcare professionals, including doctors, nurses, and dietitians, customizes the nutritional formula to meet the patient's specific needs, which can include carbohydrates, proteins, fats, electrolytes, vitamins, and minerals.
The Types of Parenteral Feeding
There are two primary types of parenteral nutrition, distinguished by the amount of nutritional support provided and the type of vein used for administration.
- Total Parenteral Nutrition (TPN): TPN provides a patient with all necessary nutrients and is used when the gastrointestinal (GI) system is completely non-functional or needs total rest. It is administered through a central venous catheter, which is placed in a large vein, typically near the heart, to handle the high concentration (osmolarity) of the nutrient solution.
- Peripheral Parenteral Nutrition (PPN): PPN provides supplemental nutrition, meaning it only offers a portion of a patient's total nutritional needs. It is administered through a peripheral vein, such as in the arm, and is used for shorter periods, typically less than two weeks. The solution has a lower concentration to prevent irritation to the smaller vein.
When is Parenteral Feeding Necessary?
Parenteral nutrition is a life-sustaining treatment reserved for specific medical conditions where the gut cannot be used safely or effectively for nourishment. The need for PN is determined by a comprehensive assessment of the patient's nutritional status and underlying health issues.
Common indications include:
- Short Bowel Syndrome: A condition caused by surgical removal of a large portion of the small intestine.
- Severe Malnutrition: When a patient is severely underweight and cannot consume enough calories orally or through enteral feeding.
- Gastrointestinal Obstructions: Blockages in the intestines caused by conditions like cancer, Crohn's disease, or surgical adhesions.
- Inflammatory Bowel Diseases (IBD): Such as severe Crohn's disease or ulcerative colitis, where the bowel requires complete rest to heal.
- Prolonged Ileus: The temporary inability of the intestine to function normally, often following major abdominal surgery.
- Other Conditions: Including high-output fistulas, severe pancreatitis, or major trauma requiring nutritional support.
How is Parenteral Feeding Administered?
The administration process for PN is meticulous and requires sterile technique to prevent infection.
- Preparation: The nutrient formula, typically a 3-in-1 solution containing dextrose, amino acids, and lipids, is prepared in a sterile environment.
- Access Device Placement: A catheter is inserted into a vein. For TPN, a central line (like a PICC line or tunneled catheter) is used. For PPN, a standard peripheral IV is sufficient.
- Infusion: The solution bag is connected to the catheter via a pump, which administers the nutrition at a precise rate over a set period, often 10-12 hours, typically overnight.
- Monitoring: The patient's vital signs, blood glucose, and electrolyte levels are carefully monitored throughout the treatment.
- Catheter Care: Regular dressing changes and sterile handling of the catheter site are crucial to minimize the risk of infection.
Comparison: Parenteral vs. Enteral Feeding
| Feature | Parenteral (PN) | Enteral (EN) |
|---|---|---|
| Route of Administration | Intravenous (into a vein) | Into the gastrointestinal (GI) tract via a feeding tube (e.g., NG tube, G tube) |
| GI System Requirement | Bypasses the GI system completely | Requires a functioning GI system |
| Indications | Non-functional or severely compromised gut | Unable to eat or swallow but has a functioning gut |
| Solution Concentration | High concentration (high osmolarity) | Less concentrated than PN formulas |
| Duration of Use | Short-term or long-term, potentially lifelong | Short-term or long-term |
| Associated Risks | Higher risk of infection, metabolic complications, and liver disease | Lower risk of infection and fewer metabolic complications |
| Cost | More expensive due to compounding and sterile administration | Less expensive than parenteral nutrition |
Risks and Complications
While life-saving, parenteral feeding is not without risks. Potential complications include:
- Infection: Catheter-related bloodstream infections are a major concern due to the direct access to the bloodstream.
- Metabolic Issues: The body's blood sugar and electrolyte balance can be affected, leading to hyperglycemia or hypoglycemia, or imbalances in potassium, magnesium, and calcium.
- Liver and Gallbladder Problems: Long-term use can lead to liver dysfunction or gallbladder issues due to a lack of digestive stimulation.
- Mechanical Complications: Problems related to the catheter, such as blood clots, leakage, or displacement.
- GI Atrophy: The digestive tract can atrophy from disuse over time, though function typically returns gradually after transitioning back to enteral or oral feeding.
The Transition Away from Parenteral Feeding
When a patient's GI tract function improves, a gradual transition from parenteral to enteral or oral feeding is initiated. This process is carefully monitored by the healthcare team to prevent complications like refeeding syndrome and ensure the gut can tolerate the reintroduction of food. A slow "weaning" process allows the digestive system to recover and function normally again.
Conclusion
In summary, the meaning of parenteral feeding is the intravenous delivery of nutrients, a crucial medical therapy for patients unable to use their digestive system. It is a complex process with different types—TPN and PPN—and is indicated for serious medical conditions. While it offers a vital lifeline, strict protocols are necessary to manage the associated risks. Ultimately, the goal is always to transition the patient back to more natural forms of nutrition as soon as clinically possible, highlighting its role as a powerful, albeit temporary or supplementary, form of nutritional support.
Mayo Clinic's Home Parenteral Nutrition guide provides further detail on long-term management
