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(Total) Parenteral Nutrition

(Total) Parenteral Nutrition. 20 May 2011. Indications. Non-functioning GIT to prevent malnutrition or those requiring bowel rest Obstruction Short bowel syndrome / intestinal failure Peritonitis, ileus Mesenteric ischaemia, GI fistula Congenital abnormalities Prolonged, severe diarrhoea

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(Total) Parenteral Nutrition

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  1. (Total) Parenteral Nutrition 20 May 2011

  2. Indications • Non-functioning GIT to prevent malnutrition or those requiring bowel rest • Obstruction • Short bowel syndrome / intestinal failure • Peritonitis, ileus • Mesenteric ischaemia, GI fistula • Congenital abnormalities • Prolonged, severe diarrhoea • Decision to start TPN depends on severity of illness, current weight and expected length of illness / hospital stay • Some cancer patients (treatment against weight loss)

  3. Short Bowel Syndrome • Inadequate intestinal absorptive surface leads to malabsorption, excess water loss, electrolyte derangement and malnutrition • SBS occurs with <200cm of small bowel, but if the IC valve is present this can be <150cm • It can also occur from functional abnormalities, e.g. severe inflammation or poor motility • At least 120cm of small bowel is required for an adult to be independent of TPN

  4. Intestinal Failure • Bowel <120cm in adults • Most common causes in children are: • NEC • Gastrochisis • Volvulus • In adults: • Crohn’s • Massive resection of bowel due to mesenteric vascular thrombosis • Trauma

  5. Infusion Technique • Parenteral feeding through a peripheral vein is limited by osmololity and volume constraints • >3% amino acids and 5% glucose (290kcal/L) are poorly tolerated peripherally, so 20% parenteral fat can be given to increased calories • 60g of protein and 1680kcal requires 2.5L • Peripheral vein only used therefore when supplementing enteral feeding • Adding 1000U/L of heparin may help osmolarity

  6. Insertion Technique • PICC lines can be used short term to give 20-25% dextrose and 4-7% amino acids • These avoid the complications of central lines • But they can’t be replaced • Central lines are preferred if critically ill (subclavian is best tolerated, easiest to access and dress, but jugular is less likely to cause pneumothorax)

  7. Mechanical Complications • Central line can cause pneumothorax, arterial puncture, injury • Radiography needed to confirm placement in SVC • Thrombosis can occur at site of entry and encase catheter (give 6000U of heparin daily while in hospital + warfarin for long-term use)

  8. Metabolic Complications • Hyperglycaemia • Hypertonic dextrose = massive insulin increase, leading to sodium and fluid retention • If total fluid intake exceeds 2L/d, fluid retention is likely with normal renal function • This can be reduced by using both glucose and fat in the PN solution • Insulin spike can cause refeeding syndrome (increased K, Mg, phos) so best to start PN <200g glucose/day and assess glucose tolerance • Insulin can be added to PN formula • Acid base imbalance, often due to renal tubular impairment • NG drainage can cause hypochloraemic alkalosis also

  9. Complications - Infection • Infections in central access catheter rarely occur within first the 72hr, so fever is usually due to another cause • If there is a fever after this time, the access wire should be changed and the catheter cultured • C. albicansis very common • Central catheter infection has a mortality os 12-25% and should occur <3/1000 catheter-days

  10. HPB Complications • Hepatic dysfunction is very common, it can result in hepatomegaly and jaundice • Factors such as infection, malnutrition, use of hepatotoxic medications can contribute to this, but the suspected cause is excess glucose calories and impaired hepatic triglyceride seretion • In adults, AST and ALT will raise within 2-3 weeks and reverse within10-14 days of cessation of TPN. Prolonged TPN will raise ALP and bilirubin due to steatosis • In infants, chronic liver disease arises due to cholestasis • Biliary sludge, cholelithiasis and calculous / acalculouscholecystitis are very common • 100% of patients on TPN get gall bladder sludge after 8-13 weeks • Reduced gall bladder contractility can contribute to this

  11. Intestinal Transplantation • This is the least performed transplantation within high rejection rates and low graft survival rates • Patients with intestinal failure have no survival advantage with transplant vs. medical therapy • Monitoring rejection is difficult, there are no serum biomarkers • Breakdown of the mucosa in acute rejection gives pathogens access to the bloodstream • Indicated where there is irreversible intestinal failure not successfully managed by TPN due to 1. malnutrition / FTT or 2. life-threatening complications

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