Parenteral Nutrition Overview

Parenteral Nutrition

• Parenteral nutrition (PN) provides nutrients intravenously
• Used for patients unable to take adequate nutrients orally or through enteral methods.
• Patients considered for PN are malnourished or have the potential to be.
• PN is also for those not suitable for enteral nutrition.

Types of PN

• Central PN: infused into the superior vena cava. Osmolarity is >900 mOsm/L.
• Peripheral PN: infused into peripheral veins. Osmolarity is maximum 600-900 mOsm/L.

Indications for PN

• Non-functioning or inaccessible gastrointestinal (GI) tract
  • Short bowel syndrome
  • Non-operative mechanical bowel obstruction
  • Multiple enterocutaneous fistulae (ECF)
  • Paralytic ileus
  • Severe radiation enteritis
  • Small bowel transplantation (immediately postoperative)
  • Diarrhea refractory to medical interventions
  • Critical illness with poor enteral tolerance or accessibility
  • Multi-organ dysfunction syndrome (MODS)
  • Major trauma or burns
  • Acute respiratory failure with ventilator dependency and GI malfunction

Short Bowel Syndrome

• Loss of intestinal surface for nutrient absorption due to surgical removal of bowel sections.
• Patients with less than 180-200 cm of functional small bowel often require long-term PN.

Enterocutaneous Fistula (ECF)

• Fistula: Abnormal connection between two epithelial surfaces.
• ECF occurs between the intestines and skin.
• Content leakage often from surgical procedures like tumors, irradiation, or inflammation.
• Classified by output volume:
  • High (>500 mL/day)
  • Moderate (200-500 mL/day)
  • Low (<200 mL/day)

Contraindications

• Functional GI tract (if the GI tract works, use it)
• Inability to obtain venous access
• Terminally ill patients (consider patient/family preferences)
• Situations where the risks outweigh the benefits.

Peripheral Parenteral Nutrition (PPN)

• Delivers nutrients peripherally (arm or hand veins).
• Used for short-term therapy (<2 weeks).
• May not fully meet nutritional needs, often used for transition.
• Osmolarity not exceeding 800-900 mOsm/L.

Central Parenteral Nutrition (CPN)/TPN

• Long-term therapy (weeks to years).
• Requires large-diameter central venous access (CVC).
• CVC insertion can be short-term into subclavian or jugular veins.
• Peripherally inserted central catheters (PICCs) are for moderate-term access, often inserted into an arm vein, threaded into the vena cava.
• Tunneled catheters like Hickman, Broviac, or Groshong are long-term (often years) surgically inserted catheters.
• Implantable ports (like a Port-a-cath) provide long-term, surgically implanted, subcutaneous access.

PN Admixture

• Includes dextrose, amino acids, electrolytes, vitamins, and minerals.
• Lipids can be administered separately ("piggy-back").
• "3-in-1" or "2-in-1" are solutions containing multiple nutrients in one container

Protein

• Goal: provide enough protein to maintain lean body mass.
• Amino acid concentrations in PN solutions vary (3.5-20%).
• Lower concentrations are for PPN, higher for central administration.

Carbohydrates

• Provide adequate amounts to reserve protein from catabolism, without causing hyperglycemia.
• Dextrose monohydrate is a common source, available in concentrations from 5 to 70%.

Lipids

• Essential fatty acids for patients receiving PN.
• Available in 10%, 20%, and 30% formulations (varies by mL).

Vitamins and Trace Elements

• Important for maintaining nutritional needs.
• Water-soluble and fat-soluble vitamins typically included.
• Trace minerals are usually added as preparations with several elements.

Electrolytes

• Usually added individually or in standard amounts per liter of fluid, considering the clinical needs.
• Includes sodium, potassium, calcium, magnesium, phosphate, and chloride.

Estimating PN Solution Osmolarity

• Osmolarity is essential for safe PN administration.
• Peripheral PN solutions usually remain below 800–900 mOsm.
• Central PN solutions often exceed 900 mOsm.

Administration

• Continuous infusion or cyclic administration.
• Continuous is usually with a pump, with initial rate gradually increased.
• Cyclic infusion often over 8-12 hrs to manage fluid tolerance (especially for dextrose).

Complications of PN

• Mechanical: Catheter occlusion, thrombosis, misplacement, perforation, pneumothorax, damaged catheter.
• Metabolic: Electrolyte issues, glycemic issues (hyper or hypo), hypertriglyceridemia, essential fatty acid deficiencies, bacterial overgrowth, metabolic bone disease, refeeding syndrome.
• Infections and sepsis: contamination, infection at the catheter entry site, potential increase to morbidity, mortality, and length of hospital stay.

Transitioning from PN

• Gradually transition to enteral nutrition (EN) and/or oral feeding as tolerated.
• Slow increase in EN rates to establish GI tolerance.
• Discontinue PN when patient meets nutrient requirements (usually 75% through EN/oral feeding in stable patients, 100% in malnourished patients).

Explore the essential concepts of parenteral nutrition (PN) including types, indications, and applications for patients unable to absorb nutrients orally. This quiz covers central and peripheral PN, along with various medical conditions that necessitate the use of PN. Test your understanding of this critical nutrition method.