Parenteral Nutrition (PN)

Overview

Provision of nutrients intravenously.
Used for patients unable to consume adequate nutrients orally or through enteral nutrition (EN).
- Malnourished patients or those at risk but not candidates for EN.

Principal Forms

Central PN (CPN): Infused into a central vein with mOsm/L > 900.
Peripheral PN (PPN): Infused into a peripheral vein with a max mOsm/L of 600-900.

Indications for PN

Non-functioning or inaccessible GI tract.
Clinical scenarios:
- Short bowel syndrome, bowel obstruction, enterocutaneous fistulae, paralytic ileus, severe radiation enteritis.
- Small bowel transplantation post-op, refractory diarrhea, critical illness, multi-organ dysfunction syndrome, major trauma/burns, acute respiratory failure.

Specific Conditions

Short Bowel Syndrome: Less than 180-200cm of functional small bowel, common among long-term home PN patients.
Enterocutaneous Fistula: Communication between intestinal tract and skin, often post-surgery.
- Classified by output: High (>500 mL/day), Moderate (200-500 mL/day), Low (<200 mL/day).

Contraindications

Functional GI tract should be used if possible.
Inability to obtain venous access, terminal illness without favorable prognosis, or risks outweigh benefits.

Types of PN

Peripheral Parenteral Nutrition (PPN)

Large volume dilute solution.
Short-term (less than 2 weeks).
Used as a temporary solution before central access is established.
Infusion through peripheral catheter, difficult to maintain long-term.

Central Parenteral Nutrition (CPN) / Total Parenteral Nutrition (TPN)

Long-term therapy (weeks to years).
Requires central venous access via catheters (Hickman, Broviac, Groshong, PICC).

PN Admixture Components

Dextrose, Amino acids, Lipids, Electrolytes, Vitamins, Minerals.
3 in 1: All components in one container.
2 in 1: Lipid is a separate infusion.

Macronutrients in PN

Protein

Goal: Preserve lean body mass.
Concentration varies (3.5%-20%), higher in central administration.
Provides 4 kcal/g.

Carbohydrates

Use dextrose monohydrate (3.4 kcal/g).
Prevent protein catabolism, avoid hyperglycemia.
Watch for excessive carbohydrate intake.

Lipids

Available in 10%, 20%, and 30% formulations.
Composed of soybean oil, glycerol, egg phospholipid.
Monitor triglyceride levels; consider propofol kcal in calculations.

Micronutrients

Vitamins and Trace Elements

Vitamins: Both water and fat soluble.
Trace elements: Standard mixtures vary, but generally include zinc, copper, chromium, manganese, selenium.
Iron is typically not added.

Osmolarity

Important for determining suitability for peripheral vs. central administration.

Administration Methods

Continuous: 24-hour infusion, taper to avoid hypoglycemia.
Cyclic: 8-12 hour periods, allows mobility.

Complications

Infection and Sepsis

Monitor for signs like fever, hyperglycemia.
Follow protocols to reduce infection risk.

Mechanical Issues

Catheter-related complications like occlusion, thrombosis.

Metabolic Issues

Electrolyte imbalances, glycemic control, liver dysfunction, hypertriglyceridemia.

Refeeding Syndrome

Occurs when nutrition is reintroduced after malnutrition, leading to dangerous electrolyte shifts.

Monitoring

Regular monitoring of catheter site, blood tests, and nutrient levels.

Transitional Feeding

Transition from PN to EN or oral feeding requires careful management.

Case Studies

Includes examples of when PN is indicated based on patient conditions and history.

Estimated PN Solution Osmolarity

Sample calculations for osmolarity based on nutrient components.

Additives in PN

Possible to compound medications with PN solutions.

TPN Practice

Case study calculations for dosing weight, nutrient needs, and formulation of PN orders.

These notes summarize key points from the lecture on parenteral nutrition, focusing on indications, types, administration, and complications associated with PN. Understanding these concepts is crucial for clinical nutrition assessment and intervention.

Understanding Parenteral Nutrition Basics