1. Parenteral Nutrition
This session will provide an overview of parenteral nutrition.
Please see the associated chapter in the Manual, titled Parenteral Nutrition.

2. Objectives To define Parenteral Nutrition Therapy
To explain parenteral nutrition components
To describe monitoring parameters of parenteral nutrition
Objectives of this session are:
To define Parenteral Nutrition Therapy (PN).
To explain PN components.
To describe monitoring parameters of PN.

3. Definition
Parenteral nutrition is partial or total nutrition administered intravenously. A peripheral or central vein is used for access.
Parenteral nutrition is administered partially or completely through venous access, using either a peripheral vein or central venous access.

4. Indications: Parenteral Nutrition
Non-functional gastrointestinal tract
Inability to use the gastrointestinal tract
intestinal obstruction
peritonitis
intractable vomiting
severe diarrhea
high-output enterocutaneous fistula
short bowel syndrome
severe malabsorption.
Need for bowel rest
Parenteral Nutrition provides nutritional and metabolic support to patients who cannot be adequately fed orally or via enteral tube feeding. In these patients, the gastrointestinal tract is either not functioning or cannot be used.
Situations in which parenteral nutrition may be necessary include:
intestinal obstruction
peritonitis
intractable vomiting
severe diarrhea
high-output enterocutaneous fistula
short bowel syndrome
severe malabsorption.
In acute pancreatitis, parenteral nutrition can be used until adequate levels of enteral nutrition are reached or when enteral nutrition cannot be implemented.
Parenteral nutrition is also used when bowel rest is necessary for a period of time.
Parenteral nutrition is not appropriate for extending the life of a terminal patient, unless it is an exceptional situation, in which case it should be discussed with patient and/or family.
ASPEN Board of Directors. JPEN 2002; 26 Suppl 1:83SA.
Palliative use in terminal patients is controversial.
ASPEN Board of Directors. JPEN 2002; 26 Suppl 1: 83SA

5. Contraindications: Parenteral Nutrition
Ability to consume and absorb adequate nutrients orally or by enteral tube feeding
Hemodynamic instability
Whenever enteral nutrition can be established and maintained, and it meets nutritional needs, parenteral nutrition is contraindicated .
To avoid complications with fluid and electrolyte balance, patients should be hemodynamically stable.

6. Formulas: Parenteral Nutrition
Parenteral nutrition formulas contain dextrose, crystalline amino acids, lipids, electrolytes, vitamins, minerals, and trace elements.
Nutrients are available individually, in containers of amino acids and dextrose which are mixed immediately before administration or as mixed solutions in bags which contain all parenteral nutrition components.

7. Central Parenteral Nutrition
Selection depends on caloric requirements, volume to be administered and patient condition, as well as final concentration of components:
Amino acids > 5%
Dextrose > 20%
Lipids
Includes vitamins, minerals, and trace elements
Osmolality > 700 mOsm/kg H2O
The use of central venous access depends on nutritional requirements, volume to be administered, and patient’s condition, as well as the evaluation of peripheral venous access. Dextrose and amino acid content varies. This type of nutrition also provides vitamins, minerals, and necessary trace elements. The injected solution almost always has an osmolality higher than 700 mOsm/kg H2O.

8. Formulas: Parenteral Nutrition
Dextrose
Provides 3.4 kcal/g
Can be the only source of energy
Dextrose infusion rate should not exceed 5 mg/kg/min
Closely related to solution osmolality
Dextrose is the source of carbohydrates in parenteral nutrition, providing 3.4 kilocalories per gram. The dextrose component is usually from a standard 50% or 70% solution.
Dextrose can be the only non-protein source of calories or it can be administered with lipids. Dextrose as the sole source of energy is contraindicated in patients with essential fatty acid deficiency, fluid overload, poorly-controlled diabetes, or respiratory failure with hypercapnia.
Dextrose should not be administered at rates higher than 5 mg/kg/minute, which is considered to be the maximum rate at which the body can metabolize it.
Hill GL, et al. Br J Surg 1984;71:1.
Hill GL, et al. Br J Surg 1984;71:1

9. Formulas: Parenteral Nutrition
Amino Acids
Standard concentrations can vary between 5% and 15%
Energy value of amino acids (4 kcal/g)
Nitrogen (g) = protein (g) / 6.25
Amino acid solutions are available in concentrations of 5% to 15%. Typically, parenteral nutrition formulas contain solutions of 40% to 50% essential amino acids and 50% to 60% non-essential amino acids.
The approximate amount of nitrogen (grams) provided by parenteral nutrition can be calculated by dividing the total grams of protein by 6.25.

10. Sources of Protein: Parenteral Nutrition
Customize this slide for your situation. Indicate the available parenteral protein solutions for your country; i.e., standard and specialized solutions
Write speaker notes based on the amino acid solutions you indicate.

11. Formulas: Parenteral Nutrition
Lipids
Prevent essential fatty acid deficiency
Non-protein source of kcal. Recommended dose 1 g/kg/day
Available in 10%, 20% and 30% concentrations
Included as LCT or a mix of MCT/LCT at 10% and 20%
Added to basic parenteral nutrition solutions or administered individually
Lipids are used in parenteral nutrition as a non-protein source of kilocalories and to prevent essential fatty acid deficiency. Lipids are given up to a maximum tolerance of 2.5 g/kg body weight/day, with a clinical recommendation of 1 g/kg body weight/day.
In many parts of the world, lipid emulsions are available in 10%, 20% and 30% solutions, which provide 1.1, 2.0, and 3.0 kcal/mL respectively. Also, lipid emulsions often contain LCT (long-chain triglyceride) or a mixture of LCT and MCT (medium-chain triglyceride).
Lipids can be included as a parenteral nutrition component (3-in-1 solution), or administered separately through a peripheral vein, or through a Y-connector into a central venous catheter.
Trimbo SL, et al. Nutr Supp Serv 1986;6:18.
Trimbo SL, et al. Nutr Supp Serv 1986;6:18

12. Formulas: Parenteral Nutrition
Lipids
Less hyperglycemia
Lower concentrations of serum insulin
Less risk of hepatic damage
High doses can interfere with immune functions
High infusion rates can affect respiratory functions
Should be used with care in:
– Hyperlipidemia
– Symptomatic atherosclerosis
– Acute pancreatitis with hypertriglyceridemia
Parenteral nutrition solutions containing lipids are associated with less hyperglycemia, lower serum insulin concentrations, and less risk of liver injury. High doses can interfere with immune functions and high infusion rates can affect respiratory functions.
Lipid emulsions should be used according to appropriate guidelines and should be carefully monitored in patients with hyperlipidemia, symptomatic atherosclerosis, or acute pancreatitis with hypertriglyceridemia.

13. Formulas: Parenteral Nutrition
Electrolytes
Calcium, magnesium, phosphorus, chloride, potassium, sodium, and acetate
Forms and amounts are titrated based on metabolic status and fluid/electrolyte balance
Must consider calcium-phosphate solubility
Electrolytes added to PN solutions include calcium, magnesium, phosphorus, chloride, potassium, sodium, and acetate. The type and amount of each electrolyte is based on patient nutritional status, and fluid and electrolyte balance.
Sodium and potassium are available as acetate or chloride derivatives. Phosphate is available as a sodium or potassium derivative. As a general rule, magnesium is supplied as magnesium sulfate, and calcium as calcium gluconate.
When preparing PN solutions, special care should be taken to avoid calcium-phosphate precipitation, which can be potentially fatal.
Alpers DH, Stenson WF, Bier DM, eds. In: Manual of Nutritional Therapeutics. Boston: Little, Brown and Company; 1995:
Alpers DH, et al., eds. In: Manual of Nutritional Therapeutics. Little, Brown and Company; 1995

14. Formulas: Parenteral Nutrition
Vitamins and Minerals
In general, amounts below daily recommended intake for healthy people, but nonetheless sufficient to cover requirements, are added to oral or enteral formulas
Added daily to parenteral nutrition
Acute illness, infection, preexisting malnutrition, and excessive fluid loss increase vitamin requirements
Parenteral vitamin requirements differ from oral vitamin requirements due to differences in absorption, efficacy, utilization by the body, and differences in the stability of the parenteral formula. Therefore, recommendations for parenteral vitamins are generally lower than daily recommendations for healthy people.
Parenteral vitamins are added daily just before infusion to minimize losses due to light, or adsorption to the parenteral nutrition bag or tubing.
Conditions in which higher-than-recommended amounts of parenteral vitamins are required include acute illness, infection, preexisting malnutrition, or excessive fluid loss.

15. Formulas: Parenteral Nutrition
Trace Elements
Include daily zinc, copper, chromium, and manganese for patients with kidney or liver failure
Different requirements dictated by patient and pathology
Patients under extended parenteral nutrition require the addition of iron and selenium
The trace elements, zinc, copper, chromium, and manganese should be provided daily in parenteral nutrition solutions.
As with vitamins and minerals, the need for these elements varies from patient to patient, depending on the clinical problem and illness.
For patients requiring long-term parenteral nutrition, iron and selenium should also be added. Iron should not be administered to septic patients.

16. Peripheral Parenteral Nutrition
Selection of peripheral access depends on clinical situation, requirements, tolerance to volume, and final formula concentration
Osmolality < 700 mOsm/kg
Total kcal limited by concentration and ratio to volume being administered
Include ½ of the recommended electrolytes for PN
Peripheral parenteral nutrition is the provision of a dextrose solution containing amino acids and lipids through a peripheral vein.
This type of parenteral nutrition may not be as efficient as central venous parenteral nutrition, because peripheral veins do not tolerate hypertonic solutions. The osmolality of a peripherally administered solution should always be less than 700 mOsm/kg. This requirement significantly reduces the amount of kcal (especially coming from dextrose) that can be supplied.
The peripherally administered parenteral solution should provide half of the electrolytes recommended for central venous administration.
Torosian MH, ed. In: Nutrition for the Hospitalized Patient. New York: Marcel Dekker Inc.; 1995:
Torosian MH, ed. In: Nutrition for the Hospitalized Patient. Marcel Dekker Inc.; 1995

17. PN: Types of Infusion
Continuous – Total volume of formula is administered over a 24 hour period
Cyclic – Volume is administered in one period, with infusion adjustments and a period of rest
Selection of infusion type depends on patient’s condition
Use a parenteral infusion pump
When parenteral nutrition is started, the infusion should be continuous on a 24-hour basis.
Once the solution is adjusted for the patient and an appropriate fluid and electrolyte balance is achieved, parenteral nutrition can be changed to a cyclic infusion, generally administered at night for 12 to 16 hours.
Whatever the infusion method, parenteral nutrition should be administered using a parenteral infusion pump. This helps to prevent accidental administration of lethal amounts of parenteral nutrition solution.

18. Monitoring Patient on Parenteral Nutrition
Metabolic
Glucose
Fluid and electrolyte balance
Renal and hepatic function
Triglycerides and cholesterol
Assessment
Body weight
Nitrogen balance
Plasma protein
Creatinine/height index
Parenteral nutritional monitoring is used to adjust the components of the formula as well as the frequency of monitoring according to laboratory results.
As a general rule, metabolic control includes serial laboratory tests to detect possible problems such as electrolyte and fluid imbalance, hyper- or hypoglycemia, hepatic disorders, and triglyceride clearance problems. When these data are consistently within normal limits, the frequency of tests may be reduced.
Nutritional monitoring also includes daily evaluation of body weight, and weekly nitrogen balance, plasma protein levels, and creatinine/height index. These tests are done regularly for patients receiving parenteral nutrition.
Campbell SM, Bowers DF. Parenteral Nutrition. In: Handbook of Clinical Dietetics, The American Dietetic Association, 2nd ed. New Haven: Yale University Press. 1992;
Campbell SM, Bowers DF. Parenteral Nutrition. In: Handbook of Clinical Dietetics. Yale University Press, 1992

19. Summary
Parenteral nutrition supplies partial or total nutrition by venous access
Total parenteral nutrition components supply all required nutrients
Metabolic monitoring and changes in solution components are needed to maintain adequate metabolic balance
Summary:
Parenteral nutrition supplies partial or total nutrition by venous access.
Parenteral nutrition components are able to supply all required nutrients.
Metabolic monitoring and adjustments in solution components are needed to maintain adequate metabolic balance with respect to the patient’s illness and progress.