What is parenteral feeding?
Parenteral feeding, also known as parenteral nutrition (PN), is a medical procedure that provides fluid, electrolytes, and nutrients intravenously, bypassing the gastrointestinal (GI) tract. The term "parenteral" literally means "outside of the digestive tract". This approach is used for individuals who cannot absorb nutrients through their digestive system due to illness, injury, or severe malnutrition.
The components of parenteral nutrition
The liquid solution, often called a parenteral nutrition admixture, is specially formulated to meet a patient's specific nutritional needs. A hospital pharmacy prepares the solution under sterile conditions to prevent contamination. The mixture is composed of several key ingredients:
- Carbohydrates: Delivered as dextrose, this provides the body's primary source of energy.
- Proteins: Provided as amino acids, which are the building blocks for tissue repair, immune function, and muscle mass.
- Fats: In the form of lipid emulsions, these supply essential fatty acids and concentrated energy.
- Vitamins and Minerals: A comprehensive blend of essential vitamins and minerals, including trace elements like zinc and copper, ensures the body receives all necessary micronutrients.
- Electrolytes: Minerals such as sodium, potassium, calcium, and phosphate are included to maintain critical fluid and electrolyte balance.
- Water: The solution's base fluid keeps the patient hydrated and dissolves the nutrient components.
Types of parenteral feeding
Parenteral feeding is categorized based on the method of delivery and nutritional completeness. The two main types are Peripheral Parenteral Nutrition (PPN) and Total Parenteral Nutrition (TPN).
Peripheral Parenteral Nutrition (PPN)
PPN delivers a less concentrated, temporary solution through a catheter inserted into a smaller, peripheral vein, typically in the arm. Due to the lower concentration, it is used for short-term support, usually less than two weeks, and is often supplemental to other forms of feeding.
Total Parenteral Nutrition (TPN)
TPN provides all of a person's nutritional needs and is administered via a central venous catheter (central line) inserted into a large vein, such as the superior vena cava near the heart. This method is necessary for long-term or permanent nutritional support because it can deliver a more concentrated, calorie-dense solution safely.
PPN vs. TPN: A comparison
| Feature | Peripheral Parenteral Nutrition (PPN) | Total Parenteral Nutrition (TPN) |
|---|---|---|
| Delivery Site | Smaller, peripheral vein (e.g., in the arm) | Larger, central vein (e.g., subclavian) |
| Concentration | Less concentrated solution | Highly concentrated solution |
| Duration of Use | Short-term, typically less than two weeks | Long-term, potentially indefinite |
| Nutritional Scope | Supplemental, used when a patient can eat partially | Complete, provides all daily nutritional requirements |
| Risk of Phlebitis | Higher risk due to solution concentration | Lower risk for large veins |
| Catheter Type | Peripheral IV catheter | Central line (PICC, tunneled, or implanted port) |
When is parenteral feeding used?
Parenteral feeding is indicated for a range of conditions where the gastrointestinal system is unable to function properly or needs to rest completely to heal. Conditions that may require PN include:
- Gastrointestinal surgery: Restoring a patient's nutritional status before or after major abdominal surgery.
- Intestinal failure: Conditions like short bowel syndrome where significant sections of the small intestine have been removed, impairing nutrient absorption.
- Inflammatory bowel diseases: Such as severe Crohn's disease or ulcerative colitis, during an acute flare-up.
- Bowel obstruction: Blockages caused by conditions like cancer or adhesions.
- Prolonged ileus: A temporary paralysis of the bowel's muscular wall.
- Severe pancreatitis: A period of bowel rest is often required.
- Trauma or critical illness: Patients in a hypercatabolic state due to sepsis or major trauma.
- Congenital malformations: Including premature infants with immature digestive systems.
Administration and monitoring
The PN solution is delivered via an infusion pump, which precisely controls the rate of flow into the patient's bloodstream. Healthcare professionals closely monitor the patient throughout the process to prevent complications.
Monitoring typically involves:
- Regular blood tests to check blood glucose, electrolytes, and other nutrient levels.
- Daily weight measurements and monitoring of fluid intake and output.
- Evaluation of liver function tests to check for potential liver stress.
- Frequent inspection of the catheter site for signs of infection.
Potential risks and complications
While parenteral feeding is a vital treatment, it is not without risks. Potential complications require careful management by a healthcare team.
- Infection: The most common and serious risk is a bloodstream infection related to the catheter, which can lead to sepsis.
- Metabolic Issues: Patients can experience hyperglycemia (high blood sugar), hypoglycemia (low blood sugar), or electrolyte imbalances.
- Blood Clots (Thrombosis): The presence of a foreign object like a catheter can increase the risk of blood clots.
- Liver Dysfunction: Long-term PN can lead to liver complications.
- Catheter Complications: The catheter can become clogged, cracked, or dislodged.
The transition back to eating
When a patient's GI system begins to function again, the medical team will gradually wean them off parenteral feeding. This transition is carefully managed, often starting with a liquid diet and slowly progressing to solid foods. This process helps prevent complications and allows the digestive tract, which may have atrophied, to reacclimate to its normal function.
Conclusion
In summary, what does parenteral feeding mean? It is a specialized, life-sustaining medical therapy for individuals with severely impaired gastrointestinal function, ensuring they receive the full range of nutrients directly into their bloodstream. While it carries risks like infection and metabolic imbalances, a dedicated healthcare team provides careful monitoring to manage complications. For many patients, it is a crucial lifeline that provides the necessary nutrition for healing and recovery. For further authoritative information on nutritional therapies, refer to the American Society for Parenteral and Enteral Nutrition (ASPEN).
