Total parenteral nutrition (TPN) is a life-sustaining treatment that provides complete nutritional support intravenously for patients who cannot receive adequate nutrients through their digestive system. Because TPN solutions are highly concentrated, they must be infused into a large, central vein with high blood flow to prevent irritation and damage to smaller, peripheral veins. The different types of lines for TPN are categorized based on how the catheter accesses the central circulatory system and whether the device is entirely internal or has an external component.
Peripherally Inserted Central Catheter (PICC)
What is a PICC Line?
A PICC line is a thin, flexible tube inserted into a peripheral vein in the upper arm, such as the basilic or cephalic vein. It is then threaded through the vein until the tip rests in a large central vein near the heart, typically the superior vena cava. The catheter and access port remain outside the body, making it an external device.
When is a PICC Line Used for TPN?
PICC lines are a common choice for TPN when nutritional support is needed for several weeks to months. This intermediate-to-long-term access is suitable for patients requiring extended therapy but not permanent access. It can often be inserted at the bedside using ultrasound guidance, a less invasive procedure than surgically placed lines. PICC lines are also used for long-term antibiotic therapy, chemotherapy, and other medications.
Key Considerations for PICC Lines
- Placement: Can be done at the bedside by trained professionals, including doctors or specially certified nurses.
- Duration: Suitable for medium-term use, ranging from weeks up to several months.
- Patient Lifestyle: While it allows for most normal activities, contact sports and water submersion (swimming) must be avoided.
- Care: Requires frequent sterile dressing changes and regular flushing to prevent blockages.
Tunneled Catheters
What is a Tunneled Catheter?
A tunneled catheter is surgically inserted into a central vein, such as the internal jugular or subclavian. A key feature is that the catheter is "tunneled" under the skin before exiting the body at a different site, usually on the chest. This tunneling creates a longer tract for the catheter, and a small cuff is often attached to the device, which tissue grows around to help anchor it and prevent infection. Brands like Hickman and Broviac are examples of tunneled catheters.
When are Tunneled Catheters Used for TPN?
These catheters are designed for long-term TPN, potentially lasting for years. The cuff provides an extra layer of infection protection, and the tunneling makes the device more secure and less likely to be accidentally dislodged. They are a reliable option for patients requiring continuous or frequent vascular access over an extended period, such as those with chronic gastrointestinal disorders.
Implanted Ports (Port-a-Cath)
What is an Implanted Port?
An implanted port is a totally implanted venous access device, meaning everything is completely under the skin. It consists of a catheter connected to a small, self-sealing reservoir or port placed in a pocket under the skin, typically on the chest. To use the port, a special needle is inserted through the skin into the port's rubber septum.
When are Implanted Ports Used for TPN?
Ports are ideal for patients requiring long-term, intermittent TPN who lead active lifestyles. Since there is no external tubing when not in use, a port has a reduced infection risk and a minimal impact on a patient's body image. Activities like showering and swimming can be resumed once the incision site has healed. They are the most discreet and permanent option for TPN.
Comparison of TPN Lines
| Feature | PICC Line | Tunneled Catheter | Implanted Port |
|---|---|---|---|
| Placement | Inserted peripherally in the arm, threaded to a central vein. | Surgically placed into a central vein (neck/chest), then tunneled under the skin to an exit site. | Surgically implanted entirely under the skin, with the catheter tip in a central vein. |
| Duration | Medium-term (weeks to months). | Long-term (months to years). | Long-term (months to years), and often considered the most permanent. |
| Visibility | External tubing and dressing at the insertion site. | External tubing and dressing at the exit site. | Subcutaneous port is not visible when not accessed; no dressing required. |
| Infection Risk | Higher than an implanted port due to the external presence of the catheter. | Lower than a PICC due to the tissue cuff and tunneling. | Lowest risk due to being completely sealed under the skin. |
| Patient Activity | Limits certain physical activities and submersion in water. | Restricts contact sports but is more secure than a PICC. | Fewest lifestyle restrictions; allows for showering and swimming when not accessed. |
| Access Method | Direct access to the external tubing. | Direct access to the external tubing. | Requires a needle stick through the skin into the port. |
Non-Tunneled Central Venous Catheters
What are Non-Tunneled Catheters?
Non-tunneled catheters are inserted directly into a central vein, such as the internal jugular, subclavian, or femoral vein, without being tunneled under the skin. The catheter exits the body at the insertion site and is secured with sutures and a dressing.
When are Non-Tunneled Catheters Used for TPN?
These catheters are typically used for short-term TPN, lasting a few days up to a couple of weeks, especially in hospital or emergency settings. They offer quick and direct access but have a higher risk of infection and accidental dislodgement compared to tunneled or implanted devices. Due to the high infection rate, especially in the femoral vein, they are avoided for long-term use.
Peripheral Parenteral Nutrition (PPN) vs. TPN
It is important to distinguish between TPN and peripheral parenteral nutrition (PPN). Unlike TPN, PPN is administered through a smaller, peripheral intravenous catheter and is only suitable for temporary (less than 10-14 days) nutritional support. PPN solutions are less concentrated to prevent vein irritation, making them insufficient for patients who need their total nutritional intake delivered intravenously. Total parenteral nutrition, due to its high osmolarity and concentration, requires central venous access to be administered safely and effectively.
Choosing the Right Line
The choice of TPN line depends on several factors, including the anticipated duration of therapy, the patient's lifestyle, and clinical conditions. A short-term hospital stay may warrant a non-tunneled catheter, whereas a patient needing months of home TPN might receive a PICC line. For very long-term or permanent nutritional needs, especially in active individuals, a tunneled catheter or implanted port provides more security and convenience. A healthcare team, including physicians and nutrition specialists, will evaluate the best option for each patient.
Conclusion
The availability of different lines for TPN allows healthcare providers to customize treatment based on individual patient needs, safety, and lifestyle. For short-term care, non-tunneled catheters offer a quick solution, while PICC lines provide a medium-term option with simpler placement. For long-term TPN, tunneled catheters and implanted ports offer greater security and convenience, with implanted ports being the most discreet and infection-resistant choice. Understanding these options is crucial for patients and caregivers navigating intravenous nutritional therapy.
