Total Parenteral Nutrition

Total Parenteral Nutrition

Parenteral Nutrition  is pharmacological therapy, where nutrients, vitamins, electrolytes and medications are delivered through venous route, to those patients whose GIT is not functional or unable to tolerate enteral nutrition

Parenteral nutrition is process of supplying nutrients via the intravenous route

• Total parenteral nutrition (TPN)
  • Peripheral parenteral nutrition (PPN)

Goals of Parenteral Nutrition

• Maintain or improve nutritional status
• Minimize deleterious effects of catabolism
• Boost immune system
• Improve CVS and respiratory function
• Acid/base and electrolyte balance
• Rehabilitation

Calorie/Protein Yields

• 1 Gm protein = 4 kcals
  • 1 Gm fat = 9 kcals
  • 1 Gm dextrose = 3.4 kcals
  • 1 Gm nitrogen = 6.25gm protein

Peripheral Parenteral Nutrition

• Peripheral vein
• Short period < 2 weeks
• Osmolarity < 900 mOsm/L
• Lipid is an important component

      Indications

• Parenteral nutrition for short period
• Central venous catheter insertion not possible
• Sepsis in patient on TPN

      Contraindications

• Patients with increased energy requirements
• Patients who are on fluid restrictions
• Critically ill patients who will not tolerate large volume of PPN

Total Parenteral Nutrition

• More effective compared to PPN
• Via Superior venacava or Inferior venacava
• Dextrose used 50-70%, therefore hypertonic and irritant
• Catheter is made of polyurethrane (short period) and silicon rubber (long period)
• It can be Short term TPN or Long Term TPN – “Tunneled”
• System of Delivery :
  – Multiple bottle system
  – Three in one system
• Duration
  – Continuous : reserved for critically ill patients
  – Cyclic

Indications of Parenteral Nutrition

General Indications

• Inadequate nutrition for least 7-10 days
• Pre-existing severe malnutrition with inadequate oral or enteral feed

Anticipated or actual inadequate oral feeds

•  Conditions impairing absorption of nutrients
• Entercutaneous fistula
• Short bowel syndrome
• Effects of radiation and chemotherapy
•  Need for bowel rest
• Pancreatitis
• Inflammatory bowel disease
• Ischemic bowel
• Peritonitis
• Pre and post-operative status
•  Motility disorders
• Inability to achieve or maintain enteral access
• Significant multi organ failure

Nutrition requirements

Resting Energy Expenditure

Simple body weight formula :

Resting energy expenditure (REE) {kcal/day}=25 × Wt(kgs)

Harris Benedict equation

• REE(men)= 66+(13.7× Wt) + (5 × H(cms)) – (6.7×A(yrs))

• REE(women)= 655+(9.6× Wt) + (1.8 × H(cms)) – (4.7×A(yrs))

Carbohydtrates

• Mainly Dextrose
• 1gm=3.4Kcal
• Variable concentration : 5-70%
• Osmolarity: 252-1900 mOsm/L

Advantages

• Cost
• Calories
• Nitrogen sparing effect

Disadvantages

• Calories as compared to lipids are low
• Increased CO₂ production
• Thrombophlebitis

Fats

• Administered as  emulsions
• Soybean and sunflower oil
• Egg yolk phospholipids – emulsifying agent
• Glycerin – Isotonicity with plasma
• 1gm = 9 Kcal
• Available as 10, 20 & 30%
• Requirements 20-30% of total REE

Advantages

• Calories
• Glucose and nitrogen sparing
• Less carbon dioxide
• Prevention of EFA deficiency
• Less risk of thrombophlebitis

Contraindications

• Hyperlipidemia TG > 350 mg/dl
• Acidosis pH < 7.3
• Anemia
• Intravascular coagulation
• Impaired circulation

Duration :

• If used to prevent EFA deficiency – 3-4days/week
• If used as calorie source – daily

Proteins

• 1gm = 4 Kcal
• 50% EAA + 50% NEAA – standard preparation
• Concentration range 3 – 15%

Advantages

• Calorie supplement
• Protein synthesis
• Decreases rate of catabolism

Contraindications

• Hepatic insufficiency
• Renal failure
• Metabolic or respiratory alkalosis

Monitor Nitrogen balance = Nitrogen intake – Nitrogen loss

Nitrogen loss = {(24 – urine urea Nitrogen  + 4) × 6.25 }

+ve Nitrogen  balance = anabolism

-ve Nitrogen balance = catabolism

Disease specific modifications

• Hepatic insufficiency

Branched chain amino acids (BCAA ) = leucine, isoleucine & valine

• Renal Failure

Large amount of Essential amino acids(EAA)

• Volume overload

15% concentrated amino acid solution

Special formulations

Immunomodulators

• Glutamine
• Omega 3 Fatty Acid
• Arginine
• Vitamins
• Electrolytes
• Trace elements

Complications of  TPN

• Acid-base imbalance
• Dehydration
• Elevated serum triglycerides
• Failure to induce anabolism
• High serum lipid concentrations
• Hyperammonemia
• Hyperglycemia or hypoglycemia
• Hypoalbuminemia
• Imbalance of electrolytes
• Liver toxicity
• Catheter Sepsis

Designing Parenteral Nutrition formula

3 steps

1. Calculation of daily requirements
2. Convert requirement into prescription
3. To prepare PN solution as per prescription

Step 1

• Fluid requirements = 35ml/Kg
• 35 × Wt(60kgs) = 2100ml
• Calorie = 25 Kcal/kg/day = 25 × 60 = 1500Kcal/day
• Proteins needed for a stable patient is 1gm/kg = 60gms/day
•         1gm = 4 Kcal
•         60gms = 240 Kcal
• Fats = 30% of energy = 30% of 1500 Kcal = 450 Kcal
• 1gm = 9 Kcal
• Therefore 450 Kcal = 450 / 9 =  50gms
• Carbohydrates = 1500 – (450 + 240) = 810 Kcal
• 1gm Carbohydrate = 4 kcal
• Therefore 810 Kcal = 810 / 4 =  202.5gms

Step 2

Determine volume of lipid emulsion

• Select 10 % emulsion
• Fluid volume (ml) = amount of substance (gms) / concentration (%) × 100
• 50 / 10 × 100 = 500ml
• 500ml of 10% emulsion of fat

Determine volume of proteins (10%)

• Fluid volume (ml) = amount of substance (gms) / concentration (%) × 100
• 60 / 10 × 100 = 600ml
• 600ml of 10% solution of amino acid

Determine concentration and volume of dextrose

•  Fluid volume (ml) = amount of substance (gms) / concentration (%) × 100
• 2100 – (500 + 600 ) = 1000ml
• 1000 = 20 / concentration (%) × 100
• Concentration = 20 / 1000 × 100  = 20%

 

Osmolarity limits

• Peripheral: 600-900 mOsm/L
  • Total: > 1800 mOsm/L

Increased osmolarity limits allows for increased concentrations of dextrose and amino acids to be delivered

Osmolarity of additivies (per 1% final concentrations)

• Amino acids: 100 mOsm/L
  • Dextrose: 50 mOsm/L
  • Lipids: 1.7 mOsm/L
  • Electrolytes: 1-1.4 mOsm/meq

Common Additions to TPNs

Precautions

• Phosphates are  injected first and are never mixed with calcium and magnessium
• Then add amino acids, dextrose, lipids, and water
• Then add the other electrolytes
• TPN must be inspected after mixing to look for precipitates

Transition to enteral or oral feeds

• Ultimate goal = switch to oral
• Gradual not abrupt
• Once patient can take 60% of total calorie requirements orally, Parenteral Nutrition can be stopped
• Before stopping Parenteral Nutrition infusion rate is decreased to 50% for 2-4hrs