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Enteral Nutrition


The term enteral refers to feeding via gut, and hence includes normal feeding, but in present context it refers to the infusion of chemically designed formulae via a tube into the upper GIT.

  1. Parenteral Nutrition:
    1. The term refers to the infusion of nutrient solution into the blood stream (by-passing the gut).
    2. Parenteral nutrition is provided by a central vein or by a peripheral vein. 
  2. Indications
    1. DEVELOPMENTAL ANOMOLIES OF GUT: Newborn infants with gut anomalies, like: TOF, Gastroschisis, Omphalocele, Massive intestinal atresia.
    2. PROTRACTED DIARRHOEA OF INFANCY: Infants who fails to thrive either nonspecifically or secondary to GI insufficiency, like: Malabsorption, Enzyme deficiency, Meconium ileus, Short bowel syndrome or idiopathic diarrhoea of infancy.
    3. Established or clinically predictable malnutrition, when the gut is not usable for >7 days.
    4. Adult patients with short bowel syndrome secondary to massive small bowel resection, entero-enteric, entero-colic or entero-vesical fistulae.
    5. Patients with high alimentary tract obstruction without vascular compromise, secondary to achalasia, stricture or oesophageal/gastric malignancy or pyloric obstruction.
    6. Patients with prolonged ileus following major surgeries, multiple injuries, blunt or open abdominal trauma.
    7. Malabsorption in spite of normal gut length, like: sprue, ulcerative colitis, pancreatic insufficiency, regional enteritis, tuberculous enteritis or granulomatous colitis (Major portion of absorptive mucosa is lost).
    8. Patients with functional GI-Disorder, like: Oesophageal dyskinesia following CVA, idiopathic diarrhoea, psychogenic vomiting.
    9. Patients with excessive metabolic requirements because of severe trauma like: deep burn, multiple major fractures or soft tissue injuries, Radiation enteritis
    10. Intractable vomiting
    11. Facio-maxillary trauma.
  3. Contraindications For TPN
    1. LACK OF SPECIFIC GOAL: where instead of extending a meaningful life, inevitable dying is prolonged.
    2. PERIODS OF CARDIOVASCULAR INSTABILITY, or severe metabolic derangements requiring control of correction before attempting hypertonic intravenous feeds.
    3. Acute Hepatic Failure
  4. Feasibility Of Gut Feeding.
    1. Patients in good nutritional states, in whom only a short-term nutritional support is anticipated.
    2. Infants with less than 8 cm. of small bowel
    3. Patients who are irreversibly decerebrate or otherwise dehumanized. 

Assessment Of The Patient (Prior to initiation of TPN)


Method of assessment

Moderately malnourished

Severely malnourished

Ideal Weight



Creatinine Height Index

(24 Hrs urinary creatinine ×100

Ideal for height & sex)



S. Albumin (mg/dl)



S. Transferrin (mg/dl)



TLC (cmm)



Delayed Hypersensit. Index *



Prognostic Nutritional index #




Delayed hypersensitivity index quantitates the amount of induration elicited by skin testing with a common antigen such as candida, trychphyton or mumps.


Induration grade:     0= < 0.5 cm.;  1= .5 cm.         2= 1cm.


PMI % = 158-1.66 × albumin (gm/l) – (0.78 × triceps skin fold in mm.)- (2 × transferrrin gm/l) – 5.8 × delayed hypersensitivity index)

  1. Requirements To Be Calculated.
    After assessing the nutritional status of the patient, requirement is calculated in terms of:
    1. Fluid requirement                
    2. Energy Requirement
    3. Protein or AA requirement           
    4. Mineral & Vitamin.
  1. Fluid Requirement: Q
    Normal Daily fluid requirement:
    Infants: 120ml/kg body weight. Adults: 40ml/lg body weight.
    For each 0oC rise of Temp. add 200 ml/day.
    Abnormal losses are added to daily requirements. 
  2. Energy Requirement:
    1. Patients Basal Energy Expenditure (BEE) is calculated using Harris Benedict Equation.
    2. For women: 655.10 + 9.56 (W) + 1.85 (H) - 4.68 (A) Kcal/day
    3. For men: 665.47 + 13.75 (W) + 5 (H) - 6.76 (A) Kcal/day
    4. W= wt. In Kg.  H= height in cm.       A= age in years.
    5. To the BEE should be added:
    6. A value of 20% of BEE for a pt. without significant metabolic stress.
    7. 50% of BEE for patients with marked stress like sepsis and trauma.
    8. 100% of BEE for pt. with severe stress like >40% burn.
    9. Harris Benedict equation is based on the data related to healthy subjects. So it may not correctly assess the caloric need of a hospitalized malnourished patient. Here assessment of Resting energy expenditure Q  is a better guide.
    10. Men REE: (789 × BSA) + 137
    11. Women REE: (544 × BSA) + 414
      BSA is Basal surface area.        
    12. A factor of 20% above REE estimates the need of most of the hospitalized patients, and 40-100% above REE for >40% burn. 
  3. Protein And Amino-Acids Requirement:
    1. Recommended dietary protein allowance:
      1. In non-stressed patients = 0.8 gm/kg body wt./day.
      2. Catabolic patients require = 1.2-1.7 gm/kg body wt./day
        • Protein balance = Protein intake – protein loss
        • Protein loss = 24 hrs. Urine urea nitrogen (g) × 6.25.
        • 6.25 Gm of protein = 1 Gm of nitrogen.
        • Calorie to nitrogen ratio should be 100-150: 1 (To minimize protein catabolism).
      1. The parenteral requirement of some of the vitamins may be higher than the enteral requirements, due to:
        • The micronutrients are delivered into the systemic rather than portal system thereby by-passing the liver and rapidly excreted by the kidneys.
        • Many patients requiring TPN have large GUT losses that results in Na, CL, K, and bicarbonate wasting and also loss of divalent cations and vitamins.
        • The tubing and exposure to the oxygen and light can also absorb and destroy vitamins (eg. Vit. A) before it reaches the patient.
  1. Prescribing Parenteral Nutrition: - Steps are:
    1. Step I:     Calculate patient’s expenditure for caloric need & protein need.
    2. Step II:    identify appropriate amount of Dextrose/ Fat Calorie and amount of amino acids to supply nitrogen acid.
    3. Step III:   Order necessary electrolyte, mineral, vitamins & trace elements.
    4. Step IV:   Calculate fluid need in which TPN will be given.
  1. Dextrose-
    1. In TPN concentrated Dextrose or Glucose is the most commonly prescribed caloric source.
    2. Dextrose provide 3.4% Kcal/gm.
    3. Thus 500 ml of 50% Dext. Supplies 850 Kcal.
    4. The basic conc. Of dext. is final solution = 20-25% dextrose.  
  2. Fat-
    1. Fat is needed to prevent essential fatty acids deficiency and also as a source of non-protein calories.
    2. Fat provides 9 Kcal/gm.
      1. Its available as 10% & 20% emulsion providing 1.1 & 2 Kcal/ml.
      2. Thus 500 ml of 10% fat emulsion = 500 × 1.1 = 550 Kcal.
      3. 500 ml of 20% fat emulsion = 500 × 2 = 1000 Kcal. 
    3. Crystalline Amino Acids: As protein source.
      1. Proteins are not provided for calories but to provide nitrogen for protein catabolism.
      2. 6.25 gm of protein contain 1 gm of nitrogen.
      3. The basic solution of TPN contains final conc. of 3-5% amino acid
      4. Thus 500 ml of 10% AA = 4.63 gm of N+ or 28.9 gm of proteins 
    4. Electrolytes and mineral are provided for maintenance and to for acute loss, should include: Na+, K+, Ca++, Mg+, Cl-, Po4-
      Trace elements given daily are:
      1. 0.8 mg Manganese.
      2. 1 mg Copper.
      3. 4 mg of Zinc.
      4. 10 mg Chromium. 
    5. Adequate Vitamin supplementation should be done intravenously. Following vitamins have to be given I.M. as they are unstable in hyperalimentation solution.
      1. Vit. K    = 10 mg / Week.
      2. Folic acid = 5 mg / week
      3. Vit B12 = 1 mg / month
      4. 3 In 1 TPN solution: combine glucose fat AA and other additives in One bag for infusion over 24 hours.
  • Advantages:    
    1. Decreased risk of infection Due to less manipulation/ Cost saving/ Time saving
    2. Using a glucose, and fat calorie source provides a more physiologic solution > reduced co2 production.
    3. In this solution up to 40% kcal may be given as fat.

Example: ordering TPN for 70 kg man, 170 cm height


Step I: Calculate caloric and nitrogen needs.


BSA = 1.8


REE = 7.89 × BSA + 137 = 789×1.8-137= 1557 Kcal.


20% increment: Final REE = 1867 Kcal.

  1. Calculated caloric requirement = 1867 Kcal.
    Nitrogen requirement: 70 × 1.3 gm protein = 91 gm protein.
    91 gm / 6.25 = 14.5 gm of nitrogen.
  2. Calculated nitrogen need = 14.65 gm NT.
    Step II: Ordering solution for 24 hrs. administration.
    800 ml of 50% dextrose. = 1360 Kcal
    500 ml of 10% fat. = 550 Kcal
    900 ml of 10% AA = 15.1 gm N+
    Step II: Add electrolyte mineral vitamins.
    The starting infusion rate should be 50-100 ml / hr depending to patients cardiovascular and renal status.
    This rate gives 1200-2400 Kcal / day.
    The increase should be 25-50 ml / hr. every day to allow kidney and pancreas to adjust to increased osmolality and glucose level.
Specific Formulations In Specific Disese State:
  1.  TPN in patients with Renal Failure:
    1. Patients in ARF not requiring dialysis require Concentrated TPN, (eg. Glucose-10%, Fat-20%, AA-10%), to reduce fluid load yet to provide adequate calories to prevent catabolism.
    2. Nitrogen conc. should be less.
    3. After regular dialysis is established protein content can be liberalized to provide 1-1.5 gm protein / kg / day.
  2. In hepatic failure (Chronic):
    1. Here ureagenesis is impaired with accumulation of toxic nitrogenous compounds eg. Ammonia
    2. Thus TPN is started with a reduced load of protein (0.7 gm/kg)
    3. Solution should contain more of branched chain AA and less of aromatic AA.
    4. Such solution appears to improve encephalopathy though it may not improve survival dictated by underlying liver failure.  
  3. In cardiac or respiratory failure.
    1. Fluid and Na+ restriction is indicated in CCF.
    2. In respiratory failure, a TPN solution may provide benefit, which contains higher percentage of calories as fat. (Fat has a lower RQ then carbohydrate; .07:1, thus less likely to lead to hypercapnia).
    3. 40% of non-protein calories are given as fat if hypercapnia impairs respiratory functions.

Effects Of Tpn On Gut Functions:




Effect Of Tpn


Delayed gastric emptying. Increased acid secretion


Decreased enzymes and bicarbonate


Increased Weight, DNA, Enzymes


Increased Liver Chemistry. Steatosis, Cholestosis


Increased incidence of ball stones

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