Overview
Definition:
Parenteral nutrition (PN) is the intravenous administration of nutrients, bypassing the gastrointestinal tract
Peripheral parenteral nutrition (PPN) uses peripheral veins for infusion, typically with lower osmolarity solutions, suitable for short-term use
Total parenteral nutrition (TPN) utilizes central veins for infusion, allowing for higher osmolarity solutions and long-term administration of a complete nutritional regimen.
Epidemiology:
PN is crucial in pediatric patients unable to tolerate enteral feeding, including neonates with prematurity, necrotizing enterocolitis, or congenital anomalies, and older children with malabsorption syndromes, short bowel syndrome, or severe illnesses
The choice between PPN and TPN depends on the duration of anticipated nutritional support and the patient's venous access.
Clinical Significance:
Adequate nutritional support is vital for growth, development, and immune function in pediatric patients
PN offers a lifeline for critically ill or nutritionally compromised children
Understanding the nuances of PPN and TPN, including their indications, contraindications, and potential complications, is essential for pediatric residents preparing for DNB and NEET SS exams and for optimizing patient outcomes.
Indications And Contraindications
Indications Ppn:
Short-term nutritional support (typically < 14 days)
Patients with adequate peripheral venous access
Patients not requiring high caloric/protein intake
Transition from TPN to enteral feeds.
Indications Tpn:
Long-term nutritional support (> 14 days)
Patients with inadequate peripheral venous access
Patients requiring high caloric/protein intake
Severe gastrointestinal dysfunction (e.g., short bowel syndrome, extensive GI surgery, severe malabsorption).
Contraindications Ppn:
Poor peripheral venous access
Long-term need for PN
High osmolarity solutions required
Severe fluid overload
Sepsis with compromised peripheral circulation.
Contraindications Tpn:
Functional gastrointestinal tract suitable for enteral feeding
Availability of adequate peripheral access for short-term PN
Hyperglycemia unresponsive to insulin
Severe electrolyte imbalances that cannot be corrected prior to initiation.
Composition And Administration
Ppn Composition:
Lower osmolarity solutions (< 900 mOsm/L) to prevent phlebitis
Typically contains dextrose (5-10%), amino acids (2-4%), lipids (1-3%), electrolytes, vitamins, and trace elements
Fluid volume is limited by peripheral vein capacity.
Tpn Composition:
Higher osmolarity solutions, allowing for concentrated delivery of macronutrients and micronutrients
Contains dextrose (up to 25-30%), amino acids (up to 4-5%), lipids (variable, often 1-3%), electrolytes, vitamins, and trace elements
Tailored to individual patient needs.
Administration Ppn:
Infused through peripheral veins (e.g., forearm, hand, scalp in neonates)
Requires frequent rotation of venous access sites to prevent phlebitis and infiltration
Can be infused continuously or cyclically.
Administration Tpn:
Infused through central venous catheters (e.g., PICC, CVC, umbilical venous/arterial catheters)
Allows for higher flow rates and delivery of concentrated solutions
Requires meticulous aseptic technique to prevent catheter-related bloodstream infections (CRBSIs).
Complications
Complications Ppn:
Phlebitis and thrombosis at the infusion site
Infiltration and extravasation leading to tissue damage
Limited nutrient delivery due to low osmolarity and vein capacity
Fluid overload due to high infusion rates
Risk of infection at the peripheral site.
Complications Tpn:
Catheter-related bloodstream infections (CRBSIs)
Metabolic complications: hyperglycemia, hypoglycemia, electrolyte imbalances (e.g., hyponatremia, hyperkalemia), refeeding syndrome
Liver dysfunction (cholestasis, steatosis)
Gatrointestinal atrophy
Fluid overload
Line occlusion
Air embolism.
Prevention Strategies Ppn:
Use of appropriate vein, dilute solutions, and frequent site rotation
Monitoring for signs of inflammation or infiltration
Using lipid emulsions to reduce osmolarity if feasible.
Prevention Strategies Tpn:
Strict aseptic technique for catheter insertion and maintenance
Regular monitoring of blood glucose, electrolytes, liver function, and fluid balance
Appropriate catheter care and timely removal
Cycling TPN to allow periods of gut rest.
Monitoring And Transition
Monitoring Ppn:
Close monitoring of infusion site for phlebitis, infiltration
Regular assessment of fluid balance
Basic metabolic panel and glucose monitoring.
Monitoring Tpn:
Daily assessment of vital signs, intake/output
Frequent laboratory monitoring: electrolytes, glucose, BUN, creatinine, LFTs, triglycerides, calcium, phosphorus, magnesium
Monitoring for signs of infection and metabolic derangements.
Transition To Enteral:
Gradual introduction of enteral feeds as gut function improves
Tapering PN as enteral intake increases to meet caloric needs
PPN may be used as a bridge to full enteral feeding due to lower osmolarity and less risk of significant withdrawal symptoms.
Transition To Oral:
Once enteral feeds are well-tolerated and meeting nutritional requirements, PN can be gradually discontinued
Transition from PPN to enteral feeding is generally smoother and quicker than from TPN due to fewer metabolic disturbances.
Key Points
Exam Focus:
Remember that PPN is for short-term (< 14 days) use via peripheral lines with low osmolarity (<900 mOsm/L), while TPN is for long-term use via central lines with high osmolarity, allowing for greater nutrient delivery
CRBSI is a major TPN complication
Refeeding syndrome is a risk with both, especially TPN.
Clinical Pearls:
In neonates, PPN can be administered via scalp veins or peripheral IV lines
Always consider the risk of refeeding syndrome when initiating PN in malnourished patients
Lipid emulsions can be used in TPN to increase caloric density and reduce the risk of essential fatty acid deficiency.
Common Mistakes:
Using PPN for prolonged nutritional support
Administering TPN solutions via peripheral lines, leading to severe phlebitis and extravasation
Inadequate monitoring for CRBSIs or metabolic complications
Abrupt discontinuation of PN leading to withdrawal symptoms or significant electrolyte shifts.