🍓Medical Nutrition Therapy II Unit 10 – Parenteral Nutrition: Indications and Formulas

What's Parenteral Nutrition?

• Parenteral nutrition (PN) involves providing essential nutrients intravenously when oral or enteral feeding is not possible or sufficient
• Bypasses the digestive system and delivers nutrients directly into the bloodstream
• Consists of a sterile solution containing glucose, amino acids, lipids, electrolytes, vitamins, and trace elements
• Can be customized to meet individual patient's specific nutritional requirements
• Requires careful monitoring and adjustments to prevent complications and ensure optimal nutrition support
• Typically administered through a central venous catheter (CVC) for long-term use or a peripheral venous catheter for short-term use
• Plays a crucial role in maintaining nutritional status and preventing malnutrition in critically ill or malnourished patients

Why Do We Need It?

• PN is indicated when the gastrointestinal tract is non-functional, inaccessible, or unable to absorb nutrients adequately
• Helps maintain or improve nutritional status in patients who cannot meet their nutritional needs through oral or enteral routes
• Prevents malnutrition and its associated complications, such as impaired wound healing, increased infection risk, and prolonged hospital stays
• Supports patients with conditions that impair nutrient absorption (short bowel syndrome, inflammatory bowel disease, or intestinal fistulas)
• Provides nutrition during the perioperative period when oral intake is restricted or contraindicated
• Serves as a bridge to enteral or oral feeding in patients with temporary gastrointestinal dysfunction
• Improves quality of life and clinical outcomes in patients with chronic conditions requiring long-term nutritional support

Types of Parenteral Nutrition

• Total Parenteral Nutrition (TPN): Provides all essential nutrients exclusively through the parenteral route
  • Used when the gastrointestinal tract is completely non-functional or inaccessible
  • Requires careful monitoring and management to prevent complications
• Partial Parenteral Nutrition (PPN): Supplements oral or enteral nutrition when intake is insufficient to meet nutritional needs
  • Used in combination with oral or enteral feeding to optimize nutrient delivery
  • Can be gradually weaned as the patient's oral or enteral intake improves
• Peripheral Parenteral Nutrition (PPN): Administered through a peripheral vein for short-term use (usually less than 14 days)
  • Suitable for patients requiring short-term nutritional support or with limited central venous access
  • Formulas have lower osmolarity to reduce the risk of peripheral vein irritation
• Home Parenteral Nutrition (HPN): Administered in the home setting for patients requiring long-term PN
  • Requires patient and caregiver education, specialized equipment, and ongoing monitoring
  • Improves quality of life and reduces healthcare costs compared to prolonged hospitalization

Key Components of PN Formulas

• Macronutrients:
  • Amino acids: Provide essential and non-essential amino acids for protein synthesis and tissue repair
  • Glucose: Serves as the primary energy source and helps maintain blood glucose levels
  • Lipids: Provide a concentrated source of calories and essential fatty acids
• Electrolytes: Maintain fluid and electrolyte balance (sodium, potassium, calcium, magnesium, phosphate, and chloride)
• Micronutrients:
  • Vitamins: Include both water-soluble (B vitamins and vitamin C) and fat-soluble vitamins (A, D, E, and K)
  • Trace elements: Provide essential minerals (zinc, copper, manganese, chromium, and selenium) in small quantities
• Additives: May include medications (insulin or heparin) or specific nutrients (glutamine or carnitine) based on individual patient needs
• Osmolarity: Determines the route of administration (central or peripheral) and affects the risk of complications
• Compounding: PN formulas are compounded under sterile conditions to ensure safety and stability

Calculating Nutritional Needs

• Energy requirements: Estimated using predictive equations (Harris-Benedict or Mifflin-St Jeor) or indirect calorimetry
  • Adjust for stress factors, activity level, and weight goals
  • Typical range: 25-35 kcal/kg/day, depending on the patient's condition and nutritional status
• Protein requirements: Calculated based on the patient's metabolic stress, renal function, and nitrogen balance
  • Typical range: 1.2-2.0 g/kg/day, with higher requirements in critically ill or catabolic patients
  • Adjust for renal or hepatic impairment to prevent accumulation of nitrogenous waste products
• Fluid requirements: Assessed based on the patient's hydration status, electrolyte balance, and underlying medical conditions
  • Typical range: 30-40 mL/kg/day, with adjustments for fluid losses or restrictions
• Electrolyte and micronutrient requirements: Determined based on the patient's age, sex, and specific clinical conditions
  • Monitor serum levels regularly and adjust the PN formula accordingly to maintain normal ranges
• Refeeding syndrome: Consider the risk of refeeding syndrome in severely malnourished patients and adjust the PN formula gradually
  • Monitor closely for electrolyte imbalances (hypophosphatemia, hypomagnesemia, and hypokalemia) and fluid shifts

Administration Methods

• Central venous catheter (CVC): Preferred route for long-term PN administration
  • Inserted into a large vein (subclavian, internal jugular, or femoral) and advanced to the superior vena cava
  • Allows for the administration of high-osmolarity solutions and reduces the risk of peripheral vein irritation
  • Requires strict aseptic technique and regular care to prevent catheter-related infections
• Peripherally inserted central catheter (PICC): An alternative to CVC for intermediate-term PN administration
  • Inserted into a peripheral vein (basilic or cephalic) and advanced to the superior vena cava
  • Suitable for patients requiring PN for several weeks to months
  • Lower risk of complications compared to CVC, but still requires careful management
• Peripheral venous catheter: Used for short-term PN administration (usually less than 14 days)
  • Inserted into a peripheral vein (hand, forearm, or antecubital fossa)
  • Requires the use of lower-osmolarity solutions to reduce the risk of peripheral vein irritation
  • May require frequent site rotations to prevent complications
• Infusion pumps: Used to ensure accurate and consistent delivery of PN solutions
  • Programmable pumps allow for the customization of infusion rates and volumes
  • Alarm systems alert healthcare providers to potential problems (occlusions, air-in-line, or low battery)

Potential Complications

• Catheter-related complications:
  • Infections: Central line-associated bloodstream infections (CLABSIs) can lead to sepsis and increased morbidity and mortality
  • Thrombosis: Catheter-related thrombosis can occur due to endothelial damage or blood stasis, leading to venous obstruction
  • Mechanical complications: Catheter dislodgement, occlusion, or breakage can interrupt PN delivery and require replacement
• Metabolic complications:
  • Hyperglycemia: Excessive glucose infusion can lead to hyperglycemia, increasing the risk of infections and other complications
  • Electrolyte imbalances: Imbalances in sodium, potassium, magnesium, phosphate, or calcium can cause cardiac, neurological, or muscular dysfunction
  • Refeeding syndrome: Rapid initiation of PN in severely malnourished patients can cause fluid and electrolyte shifts, leading to potentially fatal complications
• Hepatobiliary complications:
  • Steatosis: Long-term PN can lead to the accumulation of fat in the liver, causing hepatic dysfunction
  • Cholestasis: Prolonged PN can cause bile stasis and the development of gallstones or biliary sludge
• Bone complications: Long-term PN can lead to metabolic bone disease, characterized by osteoporosis and an increased risk of fractures
• Psychological complications: Prolonged PN dependence can impact the patient's quality of life and lead to depression, anxiety, or social isolation

Monitoring and Adjusting PN

• Fluid balance: Monitor daily fluid intake and output, including PN volume, oral intake, and losses (urine, stool, and drains)
  • Adjust the PN formula and additional fluid intake to maintain euvolemia and prevent fluid overload or dehydration
• Glucose control: Monitor blood glucose levels regularly (every 4-6 hours initially, then daily once stable)
  • Adjust the glucose content of the PN formula or add insulin to maintain blood glucose within the target range (usually 140-180 mg/dL)
• Electrolyte balance: Monitor serum electrolyte levels (sodium, potassium, magnesium, phosphate, and calcium) daily or as needed
  • Adjust the electrolyte content of the PN formula to maintain normal serum levels and prevent imbalances
• Liver function: Monitor liver enzymes (AST, ALT, ALP, and bilirubin) and triglyceride levels weekly
  • Adjust the lipid content of the PN formula or consider cycling PN to prevent hepatobiliary complications
• Renal function: Monitor serum creatinine and blood urea nitrogen (BUN) levels to assess renal function
  • Adjust the protein content of the PN formula and fluid intake to prevent the accumulation of nitrogenous waste products
• Anthropometric measurements: Monitor the patient's weight, body mass index (BMI), and muscle mass (if possible) to assess the adequacy of nutritional support
  • Adjust the PN formula to promote the maintenance or restoration of a healthy body composition
• Transition to enteral or oral feeding: Assess the patient's gastrointestinal function and tolerance regularly
  • Gradually introduce enteral or oral feeding as tolerated, while proportionately reducing the PN volume to prevent overfeeding