Parenteral nutrition (PN) is by definition given IV. PN may be infused through a peripheral or central venous access device, depending on the osmolarity of the solution.
Peripheral PN may be infused through a peripheral venous access device. The osmolarity of the solution should be ≤ 900 mOsm/L. A solution with a higher osmolarity may cause thrombophlebitis.
Central PN requires a central venous access device for safe infusion because solutions formulated for central PN have an osmolarity > 900 mOsm/L.
PN should not be used routinely in patients with an intact gastrointestinal (GI) tract. Compared with enteral nutrition, PN has the following disadvantages:
More complications
Poorer preservation of the structure and function of the GI tract
Higher cost
Indications for Parenteral Nutrition
PN 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 (1):
Some stages of ulcerative colitis
Certain pediatric GI disorders (eg, congenital GI anomalies, prolonged diarrhea regardless of its cause)
Short bowel syndrome due to surgery
Indications reference
1. Worthington P, Balint J, Bechtold M, et al. When Is Parenteral Nutrition Appropriate?. JPEN J Parenter Enteral Nutr. 2017;41(3):324-377. doi:10.1177/0148607117695251
Nutritional Requirements and Formula Content
PN requires that patients receive water, usually 25 to 40 mL/kg body weight/day. Less water is needed for patients requiring fluid restriction, energy, amino acids, lipids, vitamins, and minerals (see table Basic Adult Daily Requirements for Parenteral Nutrition).
Children who need PN 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 Adult Daily Requirements for Parenteral Nutrition
Nutrient | Amount |
|---|---|
Water (/kg body weight/day) | 25–40 mL |
Energy* (/kg body weight/day) | |
Medical patient | 25–35 kcal |
Postoperative patient | 25–35 kcal |
Hypercatabolic patient | 30–45 kcal |
Critically ill patient with BMI 30–50 kg/m2 | 11–14 kcal/kg actual body weight |
Critically ill patient with BMI > 50 kg/m2 | 22–25 kcal/kg ideal body weight |
Amino acids (/kg body weight/day) | |
Medical patient | 1.0–2.0 g |
Postoperative patient | 1.5–2.0 g |
Critically ill/hypercatabolic patient | 1.2–2.0 g |
Continuous renal replacement therapy | 1.5–2.5 g |
Critically ill patient with class I or class II obesity | ≥ 2 g/kg ideal body weight |
Critically ill patient with class III obesity | ≥ 2.5 g/kg ideal body weight |
Minerals | |
Acetate | As needed to maintain acid-base balance |
Calcium | 10–15 mEq |
Chloride | As needed to maintain acid-base balance |
Chromium | ≤ 10 mcg |
Copper | 0.3–0.5 mg |
Magnesium | 8–20 mEq |
Manganese | 55 mcg |
Phosphorus | 20–40 mmol |
Potassium | 1–2 mEq/kg |
Selenium | 60–100 mcg |
Sodium | 1–2 mEq/kg |
Zinc | 3–5 mg |
Vitamins | |
Ascorbic acid | 200 mg |
Biotin | 60 mcg |
Cobalamin | 5 mcg |
Folate (folic acid) | 600 mcg |
Niacin | 40 mg |
Pantothenic acid | 15 mg |
Pyridoxine | 6 mg |
Riboflavin | 3.6 mg |
Thiamin | 6 mg |
Vitamin A | 990 mcg |
Vitamin D | 5 mcg |
Vitamin E | 10 mg |
Vitamin K | 150 mcg |
* Requirements for energy increase by 12% per 1° C of fever. | |
Data from American Society for Parenteral and Enteral Nutrition. Appropriate Dosing for Parenteral Nutrition (ASPEN Recommendations). 2019. Accessed August 26, 2024. | |
Solutions for Parenteral Nutrition
Individualized PN solutions may be prepared using sterile techniques. For individualized PN solutions, electrolytes may be adjusted based on laboratory results and changes in clinical status.
Standardized, commercially available PN solutions are available for institutions that do not have the resources to make individualized solutions.
Standard vitamin and trace element preparations also are available to add to PN to meet micronutrient requirements. Stability of the PN solution depends on many factors. Clinicians should avoid adding electrolytes to standardized PN solutions to avoid the risk of electrolyte precipitation. Because stability can be reduced by modifications to PN solutions, modifications (eg, adding electrolytes or other substances) should be reviewed by an experienced pharmacist.
PN macronutrient composition varies depending on solution type:
Peripheral PN: Lower amino acid and dextrose concentrations to keep the osmolarity low, with most calories from fat
Central PN: Higher amino acid and dextrose concentrations to provide more energy in less volume
Amino acid dose is based on the patient's calculated protein requirements.
Availability of mixed-oil lipid emulsions has changed the approach to lipid dosing in PN, intending to balance provision of nutrients with potential adverse effects. Soybean oil is rich in omega-6 polyunsaturated fatty acids, which have been associated with proinflammatory and immunosuppressive effects. Thus, traditional lipid emulsions of 100% soybean oil should be restricted to < 1 g/kg/day in patients who are critically ill but can be dosed up to 1 g/kg/day in patients who are stable. Mixed-oil lipid emulsions include combinations of soybean oil, olive oil, medium-chain triglycerides (MCTs), and fish oil, which have lower omega-6 polyunsaturated fatty acids and allow for higher total fat delivery. For adults (both stable and critically ill), 1 to 1.5 g/kg/day of the lipid emulsion blend of olive oil and soybean oil can be given, whereas 1 to 2 g/kg/day of the lipid emulsion blend of soybean oil, MCTs, olive oil, and fish oil can be given. In the United States, 100% fish oil lipid emulsion is not approved for use in adults, but it is used as a therapy for children with intestinal-failure–associated liver disease. Additional dosing considerations (eg, medication additives; calcium, phosphorus, and magnesium content) to ensure solution stability should be reviewed by an experienced pharmacist. The American Society for Parenteral and Enteral Nutrition has published recommendations for appropriate dosing of lipid emulsions (1, 2).
PN solution volumes, types, and concentrations vary depending on patient factors, such as concomitant disorders and age:
For patients with heart, liver, or kidney failure: Limited volume (liquid) intake
For patients with diabetes: Mixed-oil lipid emulsion, providing the upper end of the recommended dosing range to allow for reduction of dextrose delivery
For neonates: Lower dextrose concentrations (17 to 18%)
Solutions references
1. Mirtallo JM, Ayers P, Boullata J, et al. ASPEN Lipid Injectable Emulsion Safety Recommendations, Part 1: Background and Adult Considerations [published correction appears in Nutr Clin Pract. 2022 Apr;37(2):482]. Nutr Clin Pract. 2020;35(5):769-782. doi:10.1002/ncp.10496
2. Cober MP, Gura KM, Mirtallo JM, et al. ASPEN lipid injectable emulsion safety recommendations part 2: Neonate and pediatric considerations. Nutr Clin Pract. 2021;36(6):1106-1125. doi:10.1002/ncp.10778
Administration of Parenteral Nutrition
As with any central venous catheter, strict sterile technique must be used during insertion and maintenance of the catheter. The PN lumen of the central line should not be used for any other purpose. External tubing should be changed every 24 hours with the first PN solution bag of the day. The American Society for Parenteral and Enteral Nutrition recommends using a 1.2-micron in-line filter with PN to reduce exposure to particulate matter (1). Dressings should be kept sterile and are usually changed every 48 hours using strict sterile techniques.
If PN is given outside the hospital, patients and their care partners must be taught appropriate line care, PN administration, and identification of complications, including symptoms of infection. Qualified home nursing must be arranged.
PN should be advanced based on electrolyte and clinical stability. If a patient is hyperglycemic, blood glucose concentrations should be monitored and regular insulin should be provided. No other insulin type is compatible with PN solutions. The target blood glucose level for patients receiving PN is < 180 mg/dL (10 mmol/L) while the solution is infusing. Regular insulininsulin. Collaboration with an endocrinologist can help optimize management of blood glucose.
Administration reference
1. Worthington P, Gura KM, Kraft MD, et al. Update on the Use of Filters for Parenteral Nutrition: An ASPEN Position Paper. Nutr Clin Pract. 2021;36(1):29-39. doi:10.1002/ncp.10587
Monitoring of Parenteral Nutrition
An interdisciplinary nutrition team composed of a physician, dietitian, pharmacist, and nurse, if available, should monitor patients.
Complete blood count should be obtained. Weight, electrolytes, magnesium, phosphorus, blood urea nitrogen, and creatinine should be monitored often (eg, daily for inpatients, weekly for outpatients). Plasma glucose should be monitored every 6 hours until patients and their glucose levels become stable. Liver tests should be monitored at least weekly, but more frequent monitoring may be required if test results are abnormal. Triglyceride levels should be monitored at least twice/week in inpatients receiving lipid emulsions. Fluid intake and output should be monitored continuously.
When patients become stable, blood tests can be done less often. Blood tests should not be done while PN is being infused.
Full nutritional assessment (including BMI calculation, anthropometric measurements, and body composition analysis) should be repeated as often as dictated by a patient's clinical status. Adjustments to the nutritional assessment may be needed more frequently in patients who are critically ill and less frequently in outpatients who are stable and receiving PN.
Complications of Parenteral Nutrition
About 5 to 10% of patients with a PN line have complications related to central venous access.
Catheter-related sepsis rates have decreased since the introduction of CDC guidelines that emphasize sterile techniques for catheter insertion and skin care around the insertion site (1). The increasing use of dedicated teams of physicians and nurses who specialize in various procedures including catheter insertion also has contributed to a decrease in catheter-related infection rates.
Infectious complications associated with PN have been reduced by changes in PN management such as avoiding overfeeding, maintaining optimal blood glucose concentrations, and using mixed-oil lipid emulsions.
Glucose abnormalities are common. Hyperglycemia can be avoided by monitoring plasma glucose often, adjusting the insulin dose in the PN solution, and giving subcutaneous insulin as needed. Hypoglycemia can be precipitated by suddenly stopping constant concentrated dextrose
Hepatic complications include liver dysfunction, painful hepatomegaly, and hyperammonemia. These complications 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 PN 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. Fish oil lipid emulsions may be beneficial; in children, 100% fish oil lipid emulsion is a rescue therapy for this complication.
If infants develop any hepatic complication, limiting amino acids to 1.0 g/kg/day may be necessary.
Abnormalities of serum electrolytes and minerals should be corrected by modifying subsequent infusions or, if correction is urgently required, by beginning appropriate peripheral vein infusions. Vitamin and mineral deficiencies are rare when solutions are given correctly. Elevated blood urea
Volume overload (suggested by > 1 kg/day weight gain) may occur when patients have high daily energy requirements and thus require large fluid volumes. A pharmacist with expertise managing PN should review the PN solution to determine whether the volume of the solution can be reduced.
Metabolic bone disease, or bone demineralization (osteoporosis or osteomalacia), develops in some patients given PN 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
Complications reference
1. Centers for Disease Control and Prevention (CDC): Guidelines for the Prevention of Intravascular Catheter-Related Infections (2011). Accessed May 9, 2024.
Key Points
Consider parenteral nutrition for patients who do not have a functioning gastrointestinal tract or who have disorders requiring complete bowel rest.
Calculate requirements for water, energy, amino acids, lipids, vitamins, and minerals.
Choose a solution based on patient age and organ function status; different solutions are required for neonates and for patients who have compromised heart, kidney, or liver function.
Use a central venous catheter, with strict sterile technique for insertion and maintenance.
Monitor patients closely for complications (eg, related to central venous access; abnormal glucose, electrolyte, mineral levels; hepatic or gallbladder effects; reactions to lipid emulsions; and volume overload or dehydration).
