What is Total Parenteral Nutrition (TPN)?
Total Parenteral Nutrition (TPN) is a complex, intravenous nutritional therapy for patients who cannot consume or absorb nutrients through their digestive tract. It provides essential nutrients, including proteins, carbohydrates (dextrose), fats (lipid emulsions), electrolytes, vitamins, and minerals. Due to its high osmolality, TPN is always administered via a central venous catheter (CVC), such as a PICC line, rather than a peripheral IV. The administration of TPN requires specific equipment, including an electronic infusion device (EID) or IV pump and specialized tubing with an in-line filter.
The Importance of the Right TPN Tubing
Using the wrong tubing can lead to significant complications. Key considerations include the composition of the TPN solution and the potential for leaching of plasticizers, which can compromise the solution and the patient's health.
Types of Tubing for TPN
TPN administration sets come in two primary configurations, determined by the components of the nutritional solution:
- Two-in-One (2-in-1) Solutions: These solutions contain amino acids and dextrose but have lipids administered separately. The tubing for 2-in-1 solutions must include a 0.22-micron in-line filter to prevent particulate matter, air, and microorganisms from entering the bloodstream. Lipids, which are infused through a separate line, must be connected below this filter, as the 0.22-micron filter would block the larger lipid particles.
- Three-in-One (3-in-1) or Total Nutrient Admixture (TNA) Solutions: These combine all three macronutrients—amino acids, dextrose, and lipid emulsions—in a single bag. For these mixtures, a 1.2-micron in-line filter is used, which is large enough to allow the lipid particles to pass through but small enough to trap particulate matter.
It is critical to confirm agency or manufacturer protocols regarding filter pore size, as these standards can vary.
Material Considerations: DEHP-Free Tubing
Some medical tubing is made from polyvinyl chloride (PVC) and contains plasticizers, such as diethylhexylphthalate (DEHP), to make it flexible. Studies have shown that DEHP can leach from PVC tubing and into lipid-containing solutions, posing potential health risks, especially to vulnerable patient populations like neonates. For this reason, many healthcare facilities and manufacturers now use non-PVC, DEHP-free tubing made from materials like ethylene vinyl acetate (EVA) or thermoplastic elastomers (TPE). Non-PVC tubing also reduces the risk of drug sorption, where medications can be absorbed by the tubing itself.
Comparison Table: Choosing the Right Tubing
| Feature | 2-in-1 TPN Tubing (Lipid-Free) | 3-in-1 TPN Tubing (Total Nutrient Admixture) |
|---|---|---|
| Components | Amino acids and dextrose in one bag; lipids infused separately. | Amino acids, dextrose, and lipids combined in one bag. |
| Filter Pore Size | 0.22-micron filter. | 1.2-micron filter. |
| Lipid Administration | Lipids infused via a separate line, connected below the main filter. | Lipids are part of the main solution and pass through the filter. |
| Risk of Leaching | Lower, especially if using non-PVC tubing. | Higher risk of DEHP leaching if PVC tubing is used, making DEHP-free tubing critical. |
| Infection Control | Requires meticulous handling of two separate infusion sets and connection sites. | Simpler setup with a single infusion line, but still requires strict aseptic technique. |
Tubing Administration and Maintenance
Regardless of the type, TPN tubing requires strict protocols for administration and maintenance to prevent infection and ensure patient safety.
- Strict Aseptic Technique: All preparation and connections must be performed using sterile technique to prevent contamination. Patients and caregivers must be trained in proper hand hygiene and handling procedures.
- Daily Changes: TPN infusion sets, including tubing and filters, must be changed daily to reduce the risk of catheter-related bacteremia.
- Dedicated Line: The TPN line should be used for TPN infusions only. No other medications or fluids should be piggybacked into the TPN line to avoid incompatibilities that can lead to precipitation. If other medications are necessary, they should be administered through a separate lumen of a multi-lumen CVC or a different access site.
- No Abrupt Discontinuation: TPN infusions should not be stopped abruptly, especially in patients with diabetes, as this can cause a rapid drop in blood glucose levels (hypoglycemia). Pumps are often programmed to taper down the rate gradually. If a bag runs out, a dextrose-containing solution (e.g., D10W) should be temporarily hung at the same rate until the next bag of TPN is available.
Conclusion
Selecting the correct tubing for Total Parenteral Nutrition is a fundamental aspect of safe and effective nutritional therapy. The choice depends primarily on whether the TPN solution contains lipids, which dictates the necessary filter pore size. The move toward non-PVC, DEHP-free tubing is a significant safety advancement, mitigating the risk of plasticizer leaching, particularly in 3-in-1 solutions. Adherence to strict protocols for tubing changes, asepsis, and dedicated line usage is paramount for preventing complications like bloodstream infections. By understanding and implementing these guidelines, healthcare providers and patients can ensure the highest standard of care during TPN administration.
Managing drug therapy in patients receiving enteral and parenteral nutrition
