Total Parenteral Nutrition (TPN)

TPN may be the only feasible option for patients who do not have a functioning GI tract or who have disorders requiring complete bowel rest, such as the following:

• Some stages of ulcerative colitis

• Bowel obstruction

• Certain pediatric GI disorders (eg, congenital GI anomalies, prolonged diarrhea regardless of its cause)

• Short bowel syndrome due to surgery

TPN requires water (30 to 40 mL/kg/day), energy (30 to 35 kcal/kg/day, depending on energy expenditure; up to 45 kcal/kg/day for critically ill patients), amino acids (1.0 to 2.0 g/kg/day, depending on the degree of catabolism), essential fatty acids, vitamins, and minerals (see table Basic Adult Daily Requirements for Total Parenteral Nutrition).

Children who need TPN may have different fluid requirements and need more energy (up to 120 kcal/kg/day) and amino acids (up to 2.5 or 3.5 g/kg/day).

Basic TPN solutions are prepared using sterile techniques, usually in liter batches according to standard formulas. Normally, 2 L/day of the standard solution is needed. Solutions may be modified based on laboratory results, underlying disorders, hypermetabolism, or other factors.

Commercially available lipid emulsions are often added to supply essential fatty acids and triglycerides; 20 to 30% of total calories are usually supplied as lipids. However, withholding lipids and their calories may help obese patients mobilize endogenous fat stores, increasing insulin sensitivity.

Many TPN solutions are commonly used. Electrolytes can be added to meet the patient’s needs.

TPN solutions vary depending on other disorders present and patient age, as for the following:

• For renal insufficiency not being treated with dialysis or for liver failure: Reduced protein content and a high percentage of essential amino acids

• For heart or kidney failure: Limited volume (liquid) intake

• For respiratory failure: A lipid emulsion that provides most of nonprotein calories to minimize carbon dioxide production by carbohydrate metabolism

Because the central venous catheter needs to remain in place for a long time, strict sterile technique must be used during insertion and maintenance of the TPN line. The TPN line should not be used for any other purpose. External tubing should be changed every 24 hours with the first bag of the day. In-line filters have not been shown to decrease complications. Dressings should be kept sterile and are usually changed every 48 hours using strict sterile techniques.

If TPN is given outside the hospital, patients must be taught to recognize symptoms of infection, and qualified home nursing must be arranged.

insulin/L of TPN fluid.

Full nutritional assessment (including BMI calculation and anthropometric measurements) should be repeated at 2-week intervals.

About 5 to 10% of patients with a TPN line have complications related to central venous access.

Catheter-related sepsis rates have decreased since the introduction of guidelines that emphasize sterile techniques for catheter insertion and skin care around the insertion site. The increasing use of dedicated teams of physicians and nurses who specialize in various procedures including catheter insertion also has accounted for a decrease in catheter-related infection rates.

Glucose abnormalities (hyperglycemia or hypoglycemia) or liver dysfunction occurs in > 90% of patients.

Glucose abnormalities

Hepatic complications include liver dysfunction, painful hepatomegaly, and hyperammonemia. They can develop at any age but are most common among infants, particularly premature ones (whose liver is immature).

• Liver dysfunction may be transient, evidenced by increased transaminases, bilirubin, and alkaline phosphatase; it commonly occurs when TPN is started. Delayed or persistent elevations may result from excess amino acids. Pathogenesis is unknown, but cholestasis and inflammation may contribute. Progressive fibrosis occasionally develops. Reducing protein delivery may help.

• Painful hepatomegaly suggests fat accumulation; carbohydrate delivery should be reduced.

• Hyperammonemia

If infants develop any hepatic complication, limiting amino acids to 1.0 g/kg/day may be necessary.

Abnormalities of serum electrolytes and minerals

Volume overload (suggested by > 1 kg/day weight gain) may occur when patients have high daily energy requirements and thus require large fluid volumes.

Metabolic bone disease, or bone demineralization (osteoporosis or osteomalacia), develops in some patients given TPN for > 3 months. The mechanism is unknown. Advanced disease can cause severe periarticular, lower-extremity, and back pain.

Adverse reactions to lipid emulsions (eg, dyspnea, cutaneous allergic reactions, nausea, headache, back pain, sweating, dizziness) are uncommon but may occur early, particularly if lipids are given at > 1.0 kcal/kg/hour. Temporary hyperlipidemia may occur, particularly in patients with kidney or liver failure; treatment is usually not required. Delayed adverse reactions to lipid emulsions include hepatomegaly, mild elevation of liver enzymes, splenomegaly, thrombocytopenia, leukopenia, and, especially in premature infants with respiratory distress syndrome, pulmonary function abnormalities. Temporarily or permanently slowing or stopping lipid emulsion infusion may prevent or minimize these adverse reactions.

Gallbladder complications