What is parenteral (intravenous) nutrition?

Parenteral Nutrition: Intravenous Nutritional Support

Parenteral nutrition is a type of nutrition therapy provided through intravenous administration of nutrients such as amino acids, glucose, lipids, electrolytes, vitamins and trace elements, delivered either through a central venous line or peripheral intravenous line. 1

Types of Parenteral Nutrition

Total Parenteral Nutrition (TPN)

• Also known as exclusive parenteral nutrition
• Provides complete nutritional needs (all macro and micro-nutrients) intravenously
• No nutrition is given by any other route 1
• Indicated when patients cannot receive nutrition through the gastrointestinal tract

Supplemental Parenteral Nutrition (SPN)

• Also known as partial or complementary parenteral nutrition
• Provided in addition to nutrition through other routes (oral or enteral)
• Used when oral or enteral tube routes cannot independently achieve the nutritional care plan target 1
• Should be considered for all patients receiving less than their targeted enteral feeding after 2 days 1

Administration Routes

Central Parenteral Nutrition

• Delivered through a central venous catheter
• Required for high osmolarity formulations designed to fully meet nutritional needs 2
• Allows for delivery of more concentrated solutions

Peripheral Parenteral Nutrition

• Delivered through a peripheral intravenous line
• Limited to lower osmolarity mixtures (<850 mOsmol/L) 2
• Generally used for shorter duration or supplemental nutrition

Specialized Applications

Home Parenteral Nutrition (HPN)

• Parenteral nutrition administered outside the hospital setting
• Often used for patients with chronic intestinal failure, malignant obstruction, or partial obstruction of the gastrointestinal tract 1
• Requires extensive patient education and specialized home care support

Intra-dialytic Parenteral Nutrition (IDPN)

• Administered through the venous line of the dialysis circuit during dialysis sessions
• Used to prevent nutritional deterioration in dialysis patients when other nutrition methods are insufficient 1

Indications for Parenteral Nutrition

• When enteral nutrition is contraindicated or insufficient 1, 2
• Patients not expected to resume normal nutrition within 3 days 1
• Specific contraindications to enteral feeding requiring PN include:
  • Uncontrolled shock
  • Severe bowel ischemia
  • Bowel obstruction
  • Abdominal compartment syndrome
  • High-output fistula without distal feeding access 2

Nutritional Requirements in PN

Energy Requirements

• Target 25 kcal/kg/day, gradually increasing over 2-3 days 1, 2
• Ideally measured by indirect calorimetry for precise dosing 1
• Avoid overfeeding (>25 kcal/kg/day) in acute phase as this may worsen outcomes 2

Macronutrients

• Carbohydrates: Minimum requirement is 2 g/kg glucose per day 1
• Lipids: 0.7-1.5 g/kg administered over 12-24 hours 2
• Amino acids: 1.3-1.5 g/kg ideal body weight/day 2

Micronutrients

• All PN prescriptions should include daily doses of multivitamins and trace elements 2
• Consider evaluation of micronutrient levels after 5-7 days in high-risk patients 2

Monitoring and Complications

Metabolic Monitoring

• Maintain blood glucose <10 mmol/L to prevent infectious complications 1, 2
• Monitor for electrolyte imbalances, particularly in the initial phase
• Be aware of increased risk of hypoglycemia with tight glucose control 2

Potential Complications

• Metabolic: Hyperglycemia, hypertriglyceridemia, electrolyte imbalances 3
• Infectious: Primarily related to venous access 3
• Long-term: Hepatobiliary and bone disease with prolonged therapy 3

Implementation Best Practices

• Begin with low-dose PN in the early phase of critical illness and gradually increase to target 2
• Implement strict glycemic control protocols 2
• All patients should receive a complete formulation to cover their needs fully 1
• Avoid both overfeeding and underfeeding, as both can be detrimental 1, 2

Parenteral nutrition represents a significant advancement in medical care, evolving from a "400-year-old seemingly fanciful dream" 4 to a life-sustaining therapy for patients who cannot receive adequate nutrition through the gastrointestinal tract 3, 5, 6.