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Tpn route

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Here is a detailed breakdown of TPN routes based on surgical textbook sources:

TPN Route of Administration

Central Parenteral Nutrition (CPN) = True TPN

TPN requires access to a large-diameter central vein to deliver high-osmolarity solutions safely.
Why central?
  • TPN solutions contain 15-25% dextrose - extremely hypertonic (1800-2400 mOsm/L, ~6x more concentrated than blood)
  • Peripheral veins cannot tolerate this osmolarity - causes phlebitis and thrombosis
  • The rapid, high-flow blood in central veins dilutes the solution instantly
Common central vein access sites:
SiteDetails
Subclavian veinMost preferred - lower infection risk, patient comfort
Internal jugular veinAlternative to subclavian
Femoral veinLast resort - highest infection and thrombosis risk
PICC linePeripherally inserted central catheter - tip sits in superior vena cava (SVC)
Key point: The catheter tip should sit at the superior vena cava (SVC) / right atrial junction. - Schwartz's Principles of Surgery, 11th Ed

Peripheral Parenteral Nutrition (PPN)

Used when central access is not available or only short-term supplemental nutrition is needed.
  • Dextrose reduced to 5-10%, protein to ~3%
  • Osmolarity kept below 800-900 mOsm/L to reduce vein sclerosis
  • Still causes phlebitis with prolonged use; duration typically limited to 12-36 hours per site (or <2 weeks total)
  • NOT adequate for complete nutritional repletion or severe malnutrition
  • Restricted/prohibited in many hospital settings due to high risk of misuse - Sleisenger & Fordtran's GI and Liver Disease

TPN vs PPN at a Glance

FeatureTPN (Central)PPN (Peripheral)
Vein accessCentral (SVC)Peripheral IV
Dextrose concentration15-25%5-10%
Osmolarity1800-2400 mOsm/L<800-900 mOsm/L
DurationLong-term (weeks-months)Short-term (<2 weeks)
Full nutritional supportYesNo
Severe malnutritionAppropriateNot appropriate

Indications for TPN (Central Route)

  1. Non-functioning GI tract (bowel obstruction, ileus, short bowel syndrome, fistulas)
  2. Severe protein-calorie malnutrition with loss of GI function
  3. Supplement to enteral nutrition when EN cannot meet >60% of energy/protein goals after 1 week
  4. High-output chyle leaks (after neck dissection, etc.)
  5. Patients who are at high nutritional risk when EN is not possible
  • K.J. Lee's Essential Otolaryngology; Schwartz's Principles of Surgery, 11th Ed

Catheter Care Notes

  • A dedicated central venous catheter is used for TPN - do not use multi-lumen catheters for other medications simultaneously if possible
  • Solution prepared under laminar flow hoods in pharmacy to reduce contamination risk
  • Central line-associated bloodstream infection (CLABSI) is the major septic complication of TPN
  • Catheter placed under strict aseptic technique with position confirmed by chest X-ray before infusion begins
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