Total Parenteral Nutrition (TPN) provides calories, proteins, fats, vitamins, and minerals directly into the bloodstream through a vein. This method is used when the digestive system cannot be used to absorb nutrients, such as in cases of bowel obstruction or severe gastrointestinal failure. Because TPN delivers a complete nutritional formula, its administration requires strict adherence to medical protocols and constant safety oversight.
Establishing Vascular Access
The high concentration and osmolarity of the TPN solution, often exceeding 850 milliosmoles per liter (mOsm/L), makes it extremely irritating to the walls of smaller, peripheral veins. Delivering this highly concentrated mixture into a small vein would quickly cause inflammation, pain, and damage to the vessel. Therefore, TPN must be infused through a central venous access device (CVAD).
A central line ensures the hypertonic solution is delivered into a large-diameter vein, such as the superior vena cava. The high volume of blood flow in these veins allows for immediate and rapid dilution of the solution.
Peripherally Inserted Central Catheter (PICC)
PICC lines are inserted in the arm and threaded to the large central vein. They are often used for medium-term therapy lasting weeks or months.
Tunneled Catheters
Tunneled catheters, such as Hickman or Broviac, are surgically placed and have a segment that passes under the skin. They offer a secure, long-term option for patients requiring years of nutritional support.
Implanted Ports
Implanted ports are placed entirely under the skin and are accessed only with a needle. They are utilized for long-term TPN, providing ease of movement and infection control between infusions.
Preparation and Safety Protocols
Preparation focuses on infection prevention, as the high dextrose content in TPN creates a favorable environment for rapid bacterial growth if contamination occurs. Meticulous hand hygiene is required, involving thorough washing for at least 20 seconds or the use of an alcohol-based sanitizer before handling supplies. The work area must also be cleaned and cleared to create a sterile field.
The TPN bag must undergo visual inspection and confirmation before connection. The label must be checked against the medical order to ensure the patient’s name, formula, and expiration date are correct. The solution should be inspected for separation, cloudiness, or particulate matter that could indicate contamination; if any issues are noted, the bag must not be used.
The TPN solution should be removed from the refrigerator two to four hours before the infusion, allowing it to reach room temperature. Infusing a cold solution can cause patient discomfort, including chills and fever. Once the infusion begins, the TPN has a strict maximum “hang time” of 24 hours to minimize bacterial proliferation. All tubing and bags must be replaced at the 24-hour mark to maintain sterility.
The Infusion Process
The administration process begins with the assembly of the infusion apparatus. A new, dedicated administration set, which includes specific in-line filters, must be attached to the TPN bag. The tubing must then be “primed” by allowing the TPN fluid to run through the line to displace all air bubbles, preventing the risk of an air embolism.
An electronic infusion device (EID) or pump is necessary to control the flow rate precisely, as TPN must never be administered by gravity. The primed tubing is loaded into the pump, and the prescribed infusion rate and total volume are programmed into the device. Before connecting the line, the needleless connector on the central catheter must be thoroughly scrubbed with an antiseptic for at least 15 seconds to ensure a sterile connection site.
The tubing is securely attached to the catheter hub, and all clamps are opened before the pump is activated. For patients receiving TPN over a period shorter than 24 hours, the infusion is frequently “cycled” to mimic the body’s natural feeding rhythms. Cycling involves programming the pump to gradually increase the rate over the first hour and then gradually decrease or “taper” the rate during the final hour to avoid sudden changes in blood sugar levels.
Monitoring and Troubleshooting
Monitoring the patient and the infusion system is an ongoing requirement throughout TPN therapy to manage potential complications. The high dextrose load in the solution requires frequent monitoring of blood glucose levels, especially when starting TPN or adjusting the rate. Blood sugar checks help identify hyperglycemia, which can signal metabolic intolerance and increase the risk of infection.
Monitoring for signs of a catheter-related bloodstream infection (CRBSI) is necessary, given the invasive access and the nutrient-rich fluid. Any sudden fever, chills, or new redness, swelling, or pain at the catheter insertion site must be immediately reported. Fluid balance is also tracked by recording daily intake and output and monitoring the patient’s weight. This helps identify fluid overload, indicated by edema, rapid weight gain, or shortness of breath.
If a mechanical issue occurs, such as a pump malfunction or a leak in the tubing, the infusion should be paused immediately. A sudden stop of TPN, especially after the body has adapted to the continuous glucose supply, can cause a rapid drop in blood sugar, known as rebound hypoglycemia. If the TPN bag runs out or must be stopped suddenly, a temporary intravenous solution of Dextrose 10% in water (D10W) should be administered at the same rate to prevent this complication.