Total Parenteral Nutrition

By Dr.venkatesh kolla

Definition:

It is pharmacological theraphy where nutrients,vitamins,electrolytes and medications are delivered via the venous route to those patients whose GIT is not functioning and are unable to tolerate enteral nutrition.

Basic principles of Nutrition:

1. Avoid malnutrition.2. If the bowel works use it.(EN preferred over

TPN)3. Avoid over feeding.4. The route , timing, type of nutritional

formulation are more imp than the amount.5. Role of nutritional support is to limit protein

wasting and to supply essential and conditionally essential nutrients.

Avoid malnutrition

• It leads to increased morbidity and even mortality by increasing the chance of infection , poor wound healing , fistula formations, delayed callus formation ,pulmonary complications(dec VC and hypoxic ventilatory response),decreased tolerance to RT & CT,reduced enzyme synthesis & impaired oxidation of drugs.

• Longer recovery period and increased duration of hospitalisation.

• Poor quality of life.

AVOID OVER FEEDING ?

Over feeding causes :1. Uncontrolled hyperglycemia will produce glycosuria,

osmotic diuresis, & non-ketotic hyperosmolar dehydration and in severe cases, coma.

2. hyperglycemia increases risk of nosocomial infection.3. Excessive calories can increase O2consumption,Co2

production, minute ventilation and the work of breathing which can fatigue patients with impaired lung function.

4. Over feeding can lead to hepatic steatosis, which may lead to hepatic dysfunction.

Goals of parenteral nutrition:• To maintain or improve the nutritional status by providing

all nutrients for ongoing metabolic functions.• To minimize the deleterious effects of catabolism by

maximising the protein synthesis , limiting the protein breakdown and reducing weight loss.

• To boost the immune function & to improve wound healing.• To improve the cardiac and respiratory function by restoring

the glycogen storage of the cardiac and diaphragmatic muscles.

• To maintain or correct acid-base balance &electrolyte disturbances

• To accelerate rehab and improve the quality of life.

INDICATIONS:

A. GENERAL• In adequate oral or enteral nutrition for atleast 7-

10days.• Pre-existing severe malnutrition.B.Anticipated or actual inadequate oral or enteral intake1.Conditions that impair absorption of nutrients a.enterocutaneous fistula. b.short bowel syndrome. c.small bowle syndrome. d.effects of RT or CT.

2. Need for bowel rest: a. severe pancreatitis. b. IBD c. ischemic bowel. d. peritonitis. e. pre and post operative status.3.Motility disorders.• prolonged ileus.4.Inability to acieve or maintain enteral access a.haemodynamic instability. b.massive GI bleeding. c.Unacceptable aspiration risk. d.hyperemesis gravidarum,eating disorders.C. Significant multiorgan system disease. burns,renal,hepatic&pulmonary and etc

CONTRA INDICATIONS:

GENERAL:1. If enteral nutrition exceeds or meets the

calculated requirements.2. Patient with good nutritional status who

requires short term support.3. Severe liver failure,cardiac failure,shock and

blood dyscrasias.4. Fluid electrolyte imbalances.

DISEASE SPECIFIC:1. avoid excess carbohydrate in patients of

pulmonary compromise and in patients of ventilatory support during weaning period,as it may result in production of large amount of Co2.

2. Avoid lipid adminstration, if TG >350mg/dl or in patients of severe sepsis,moderate degree of jaudice, low platelet count(<50,000/cumm) and ARDS or severe respiratory disease

When to start parenteral nutrition?

• Even in critically patients,decision to start PN is never an emergency.

• Risk of adverse effects decreases if patient is hemodynamically stable, electrolyte abnormalities are corrected , and there are no blood glucose disturbances prior to starting PN.

• Early PN is beneficial in patients with preexisting malnutrition, critically ill patients, acute severe necrotising pancreatitis and high nutrient loss from wound and fistulas.

NUTRITIONAL REQUIREMENTS

Balance of fluid, carbohydrates, fats, proteins, minerals, trace elements and vitamins.

FLUID REQUIREMENTS:Normal requirement+abnormal losses.1500 for 20kg+20ml/kg for additional weight or

35ml/kg.Vol of fluid delivered by enteral route shud be

substracted from the estimated total requirement.

• REE: RESTING ENERGY EXPENDITURE• TEE:TOTAL ENERGY EXPENDITURE• W:WEIGHT• H:HEIGHT• A:AGE• AF:ACTIVITY FACTOR(1.2-BED REST;1.3-OUT OF

BED)• DF:DISEASE FACTOR(1.25-GENERAL SURGERY;1.3-

SEPSIS;1.6-MULTIORGAN FAILUE;1.7-30-50%BURN;1.8-50-70%BURN;2.0-7-90%BURN)

• TF:THERMAL FACTOR(1.1-38DEG,1.2-39DEG,1.3-40DEG,1.4-41DEG)

ENERGY REQUIREMENTS:

1. SIMPLE BODY WEIGHT BASED CALCULATION: REE(Kcal/day)=25 * weight 2.Harris-benedict equation:REE(man)=66+(13.7*W)+(5*H)-(6.7*A)REE(women)=65+(9.6*W)+(1.8*H)-(4.7*A)TEE=REE*AF*DF*TF3.Indirect calorimetry:REE(man)(3.9*Vo2)+(1.1*Vco2)-61

For accurate determination of energy expenditure in critical patients ,indirect calorimetry should be measured with the instrument metabolic cart.

Simple weight based calculation and HB equation over estimates the energy expenditure.

PROPORTION OF MACRONUTRIENTS:50-70% -CARBOHYDRATE20-30%-FAT10-20%-PROTEIN ,which is mainly for anabolic process.

Carbohydrate requirements:

50-70% of Total energy requirements Functions & advantages:1. Low cost: dextrose least expensive2. Supplies calories:min 100 to 150gm needed.3. Nitrogen sparing effect:glucose+

insulinreduces muscle protein breakdownand decreases hepatic glucose release.

Disadvantages:1. Low calorie supply : dextrose poor source of calorie (4kcal/gm

vs fat 9kcal/gm).2. Increased Co2 production: not preferable in patients in

respiratory disease patients.3. Thrombophelbitis: >10%D

Maximum rate of dextrose infusion is approx 5mg/kg/min or 7.2g/kg/day . if extra infusion is given there will be overfeeding consequences.

Dextrose infusion should be monitored closely, with an aim to maintain blood sugar between 120-180mg/dl.

FAT requirements:

CONTENTS: an emulsion of long chain TG’s derived from soyabean oil or combination of soyabean and sunflower oil. It also contains egg yolk phospholipids as an emulsifying agent and glycerin to achieve isotonicity with plasma. Latest contain medium chainTG.

CALORIC VALUES, PREPARATIONS AND REQUIREMENTS:20-30% Of total calories . Limit the total dose to 2g/kg/day.lipid

emulsions are available as 10%(1.1Kcal/ml),20%(2kcal/ml),30%(3kcal/ml).

A minimum of about 5% of total calories as a lipid emulsion is necessary to prevent essential FA deficiency in patients continuously receiving PN.

FUNCTIONS AND ADVANTAGES:1.CALORIE SUPPLEMENTION:major calorie fuel,important in critically

ill,volume overloaded patients2.glucose sparing, avoids hyperglycemia.3.Protein sparing.adequate calorie supplementation spares protein by

conserving body nitrogen economy and supporting protein metabolism.

4. Less Co2 production:lipid produces less Co2 and preferred in respiratory compromised patients. Respiratory quotient(RQ) of fat is 0.7<0.8protein<1 carbohydrate.RQ is ratio of Co2 production to O2 consumption.

Thus lipid emulsion has advantage of better glucose tolerance,less hyperinsulinemia,less production of Co2 and less fatty infiltration of liver.

5.Prevention of essential FA deficiency.6. Reduced risk of thrombophelbitisBecause of low osmolarity of

lipid emulsion 260mosm.

DISADVANTAGES:

High cost compared to dextrose.ADVERSE EFFECTS: Increased TG levels at very high infusion levels SEPSISwhen adminstered separately for long time. Fat embolism:Lipid is less stable when adminstered along with

aminoacids and glucose.destabilised fat particles coalesce into larger droplets to form fat emboli.

RARE :immediatedyspnea,cyanosis,nausea or vomiting,headdache,flushing,chest and backpain or thrombocytopenia.

Delayed hepatic dysfunction,fat overload,pancreatitis & delayed gastric emptying.

Contraindication

1.hypelipidemia( s.TG>350mg/dl)2.acidosis(ph<7.3)3.Anemia4. Evidence of intravascular coagulation5.Impaired circulation6.Any patients at risk of developing fat

embolism.

Rate of lipid infusion should not exceed 0.7kcal/kg/hr

PROTEIN

Aminoacids are essential components of PN.10-20% of total calorie requirement.Standard AA solution contains 40-50%

essential aminoacids and rest 50% nonessential aminoacids + semi essential AA.

10% solution contains 100gm/L.

CLINICAL CONDITION PROTEIN REQUIREMENTS(G/KG)

NORMAL 0.8

Metabolic stress (illness/injury) 1-1.5

ARF (undialysed) 0.8-1

ARF receiving dialysis 1.2-1.5

Critically ill patients 1.5

COMPENSATED CIRRHOSIS 1-1.2

HEPATIC encephalopathy <0.5

Acute sepsis 1.7

Functions and advantages1. Calorie supplement-1g-4kcal2. Protein synthesis3. Reduces rate of protein catabolism.CONTRAINDICATIONS AND ADVERSE EFFECTS:4. Hepatic insufficiency-infusion leads to metabolic

alkalosis,prerenal azotemia,increased level of ammonia,stupor or coma

5. Renal failure-leads to increased BUN.6. metabolic or respiratory alkalosis 7. Infusion at rapid rate causes nausea,vomiting, headache,

flushing,chills or fever. 5. Excess of protein or insufficent calorie supplements lead to

increased urea. renal losses of nitrogenleads to loss of H2o and may cause hypertonic dehydration.

Nitrogen balance =nitrogen intake-nitrogen lossNitrogen loss={[24-urine urea nitrogen(G)+4]*6.25}Positive nitrogen balance suggests anabolism.DISEASE SPECIFIC AMINOACIDS:A.Hepatic encephalopathybranched chain AA should be used

because there are metabolised in muscle and adipose tissue leaving liver.

Further BCAA compete with aromatic AA for the carrier,which is responsible for transport in to brain which might contribute to encephalopathy.

B. Renal failure patientslarge amounts of essential AA are recommended for patients who acute renal failure.(nitrogen of essential AA is partially recycled to produce non-essential AA.

C. For volume overloaded patients –modified solution with 15% concentrated AA base solution provides higher calorie and protein supplementation in lesser volume.

SPECIAL FORMULAS

Immune enhancing enteral diet—(glutamine, arginine and omega-3 fattyacids) was found to reduce the risk of infection, ventilator days and hospital length of stay without influencing mortality.

Glutamine helps in mucosal cell proliferation, xylose absorption and decreases permeability of gut which helps to maintain mucosal integrity and prevents translocation of bacteria and endotoxins to circulation.

So glutamine can be useful in patients with inflammatory bowel disease, a short bowel syndrome , extensive burns ,multiple trauma and septic shock .

Omega-3 fatty acids—may reduce the catabolic response of burn injury, trauma and radiation by reducing the synthesis of prostaglandins that enhances the inflammatory response.

ARGININE—Important in nitrogen and ammonia metabolism, in generation of nitric oxide and has potential role in immunomodulation.

Electrolytes , trace elements and vitamins.