Enteral Nutrition In Critically Ill

Rasha S.BondokM.D.

Anaesthesia & Intensive CareAin-Shams University

Enteral Nutrition

TerminologyEnteral nutrition = Administration of

nutrients via the existing GIT

EN is confined to tube feeding exclusively without regards to oral nutritional supplement

When is EN indicated in ICU patients?

“IF THE GUT WORKS,

USE IT OR LOOSE IT”

• All patients with functioning gut who are not expected to be on a full oral diet within 3 days

Rationale for EN…….

• Favours intestinal villous

trophicity

• Promotes gut motility

• Reduces translocation of

bacteria from gut

• Less costly than PN

Why feed the critically ill patient?

Metabolic changes occur in response to starvation, trauma and sepsis

Starvation & TraumaSkeletal muscle

Amino acids

Adipose tissue

Protein breakdown

Triglyceride

Glycerol & FFA

Glycerol

FFA

Glucose

Lactate from tissues

AminoAcids

Glucose Synthesis

Liver

SepsisSkeletal muscle

Amino acids

Adipose tissue

Protein breakdown

Triglyceride

Glycerol & FFA

Glycerol

FFA

Glucose

Lactate from tissues

AminoAcids

Glucose Synthesis

Liver

Glycogen

Ketone Bodies KetoneBodies

Nutritional Assessment as the 1st step of EN• Goal :-Detection of prior malnutrition

-Prevent/minimize further loss of BW

1. Patient history

• Disease states associated with heightened risk of malnutrition

(e. g., chronic debilitating disease)

• Recent severe loss of weight (>5% of usual body weight in 3 weeks or >10% in 6 months)

Nutritional Assessment……..

-Inadequate nutrition intake results from any of the following factors:

• Orders for nothing by mouth (NPO) x 3 days

• Clear liquid diet x 5 days

• Malabsorptive disorder

• Impaired ability to ingest

Nutritional Assessment……..2. Assessment of present condition

• Diseases associated with hypermetabolism and prolonged catabolic activity

(Multiple injuries, Burns, persistent Fever, Sepsis, MOF)

• Signs of malnutrition on physical examination (e. g., cachexia, muscle atrophy, edema)

• Body Mass Index (BW in kg/height in m2)

< 20 kg/m2

Clinical Markers of nutritional state

• Clinical Markers of nutritional state:

Widely available, sensitive, easily reproducible, highly specific

Unfortunately---No such marker is available

Clinical Markers of nutritional state• Visceral protein parameters include:

• 1-Albumin

• 2-Transferrin

• 3- Prealbumin.

• Somatic protein parameters include:

• Nitrogen balance studies

Clinical Markers of nutritional state …..Albumin

• Normal level 3.5-5g/dL

• 3-3.5g/dL—nutritional decision point

• < 3.5g/dL--- poor surgical outcome

prolonged ICU stay.

• <3g/dL ---severe malnutrition.

• <2.5g/dL---increased Mortality& Morbidity

…..Albumin• Albumin levels are low ----acute phase response

• Low albumin level is an unreliable marker of malnutrition in the critically ill.

• ½ life is lengthy 21days ------ can’t effectively monitor acute response to nutrition therapy

Clinical Markers of nutritional state …..Transferrin

• Short ½ life---8-9days

• Normal levels 200-400mg/dL

• Levels 150mg/dL—nutritional decision point

• Factors level:

e.g. Nephritic syndrome, burns, inflammation chronic infection

Clinical Markers of nutritional state …..Prealbumin• Short ½ life--- 2 days

• Normal level 16-35mg/dL

• Nutritionally significant level 11mg/dL

• <11mg/dL = Malnutrition

• Failure to increase above 11mg/dL –nutritional needs are not met

• Factors level

e.g. stress, inflammation, surgery, cirrhosis renal failure.

Nitrogen Balance

• Measures UUN and compares it to nitrogen intake during that same time

• N2 balance = N2 intake – N2 excretion or =• [24h protein (g)] – [24 h UUN (g) + 3(g)] [6.25 g nitrogen]

"fudge factor" of 3 = nitrogen losses in the faeces, skin, body fluids.

Nitrogen Balance

• If calculated nitrogen balance equals:

0 -- Nitrogen balance.

>0 -- Protein anabolism > catabolism = +ve nitrogen balance

-- Goal in nutritional repletion is +ve N2 balance

of 4-6 grams per day.

<0 -- Protein catabolism > anabolism = -ve nitrogen balance

Catabolism: starvation, trauma, surgery, inadequate nutrition therapy

Nutrition risk index • Nutrition risk index =

[1.519 x serum albumin (g/l) ]+ [0.417 x (current weight/usual weight x 100)]

>97.5 Borderline malnourished83.5 - 97.5 Mildly malnourished< 83.5 Severely malnourished

• You are asked to see a 70-year-old man on his admission to ICU with oesophageal carcinoma . You note that his serum albumin level is 22g/l , his current weight is 58kg. On questioning he remembers that his usual weight was 69kg when he was well.

• Using the nutrition risk index how would you categorise his nutritional state?

• Nutrition risk index =

[1.519 x 22] + [0.417 x {(58/69) x 100}]

=68

Severely malnourished

Contraindications of EN

• Intestinal Obstruction• Anatomic Disruption.• Intestinal Ischaemia/Perforation• Inability to access the gut eg. severe burns• Shock---reduced intestinal perfusion Unable to splanchnic blood flow in response to EN-----be cautious

• Severe diarrhea

• Protracted Vomiting Are Not Contraindications

• Intestinal dysmotility

How much EN should critically ill patient receive?• During acute initial phase of illness—

exogenous energy 20-25 Kcal/Kg/day• Excess is detrimental• During recovery phase ---30-40 Kcal/Kg/day

• Protien intake should be 1.2-1.5 g/Kg/day never exceeding 1.8 g/Kg/day Except ---extreme losses: burns, digestive losses

ESPEN Guidelines on Enteral Nutrition:Intensive care Clinical Nutrition (2006)

What length of small bowel

is necessary to maintain

adequate Enteral Nutritional

Status?

Quiz

Is early EN (< 24-48hr) superior to delayed EN in critical ill?• Critical ill who are haemodynamically stable +

functioning gut SHOULD be fed early if possible.

• Early EN------Reduction of infection.

------Reduction in hospital stay. • Early EN 12-24 hours post trauma/burn

– Reduced morbidity

– In 5 studies not 1 case of bowel infarct/ischemia in early enterally fed

Do Not Feed a Necrotic Bowel !!

• INSTEAD FEED EARLY TO PREVENT A NECROTIC BOWEL

To prevent necrotic bowel• If EN is not tolerated, TPN is needed, minimal enteral nutrition = Trophic

Feeds

< 25% of the calories provided by enteral route :

*stimulate or maintain gut function *decrease the chances of cholestasis.

• Continuous infusion 10-15 ml/h

• Bolus 6 x 50 ml/24

Access For Enteral Nutrition

• Administration Sites

• Routes For Feeding Access

Administration Site

• Gastric• Normal reservoir for food• Formula osmolality is less

of a problem• Gastric dysfunction

paresis/atony precludes feeding in the stomach :

Diabetes Drugs (Sympathomimetics, Opiates,Dopamine) Hyperglycemia - ICP Surgery & Trauma atonyfor 1-2 days but small bowelmotility is normal

• Postpyloric• Sensitive to volume• Rates >100ml/hr are not

recommended• Use isotonic formula• Recommended in patients

at risk of aspiration: Impaired gag cough reflex Mechanically Vent Neurological injury Delayed gastric emptying

Route For Feeding Access • Short Term access (for 4-6wk)---

Use Nasal Access :naso-gastric/jejunal tubes

• Nasogastric tubes:Allow use of hypertonic feeds

higher feeding rates

bolus/Intermittent feedingFine bore 8-10 F NG tubes

Access Techniques…..contNasojejunal NJ tubes• Indicated—gastric reflux

--delayed gastric emptying

--unconcious patient• Fine bore 6-10 F• Insertion same as NG, but once reached stomach,

patient is turned onto the right side advance tube 10cm

• To assist postpyloric placement of NJ tube : • 10mg Metoclopramide iv 10 min 200mg

Erythromycin iv 30min prior placement

Access Techniques…..cont• Check tube position

Access Techniques…..cont

• Long Term access > 4-6wk----Feeding Ostomies (Enterostomies)

• Percutaneous Endoscopic Enterostomy

• Surgical Enterostomy

Percutaneous Endoscopic Enterostomy

1- Percutaneous Endoscopic Gastrostomy

PEG: Method of choice

Considered in pat. with normal gastric emptying

Percutaneous Endoscopic Gastrostomy

Contraindications:Gastric cancerGastric ulcerAscitisCoagulation disorders

(Source: Kudsk KA, Jacobs DO. Nutrition. In: Surgery: Basic Science and Clinical Medicine. Norton JA, et al., eds. New York: Springer-Verlag, 2001(2) Part 7, Section 91:136)

Feeding Ostomies (Enterostomies) Percutaneous Endoscopic Jejunostomy

2- PEJ

• New—

• Technically difficult

• Indicated if postpyloric feeding is needed

• Allows concomittent jejunal feeding and gastric decompression

Administration of EN

• Bolus

• Continuous

• Intermittent

• Cyclic

Bolus Feedings

Administer 200-400 ml of enteral formula into the stomach over 5 to 20 minutes, usually by gravity with a large-bore syringeIndications:-Recommended for gastric feedings-Requires intact gag reflex-Normal gastric function

Initiation of Bolus Feedings

• Initiate with full strength formula 3-8 times per day with increases of

60-120 ml q 8-12 hours as tolerated up to goal volume; does not require dilution unless necessary to meet fluid requirements

ASPEN Nutrition Support Practice Manual, 2005

Continuous Feedings

• Administration into the GIT via pump or gravity, usually over 8 to 24 hours per day

Indications:

• Promote tolerance

• Compromised gastric function

• Feeding into small bowel

• Intolerance to other feeding techniques

Initiation of Continuous Feedings

• Initiate at full strength at 10-40 ml/hour and advance to goal rate in increments of 10 to 20 mL/hour q 8-12 hours as tolerated

• ASPEN Nutrition Support Practice Manual, 2005

Intermittent Feedings

• Administration of 200-300 ml over 30-60 minutes q 4-6 hours

Indications:

• Intolerance to bolus administration

• Initiation of support without pump

Don’t forget to water your enteral feeding patients!

• Water in Enteral Products• Calculate free water:

1kcal/ml = ~85% free water (850mL per 1,000 mL formula)

1.2-1.5 kcal/mL = 69% - 82% (690-820)

1.5-2.0 kcal/mL = 69% - 72% (690-720)

Exact water content on label or in manufact’s info

• Subtract amount of free water from needs• Provide additional water via flushes

Meeting Fluid Needs in Enterally-Fed Patients

• Water Flushes

– For Continuous feeds-- Irrigate tube q

4 hrs with 20-60 mL water

– For Intermittent / bolus feed--- Irrigate tubes before and after each feed with 20-60 mL water

– Use smaller vol for fluid-restricted pts

Enteral Feeding Tolerance Gastric Residuals

• RV--- routinely checked to assess:

-Tube feeding tolerance and

-Signify aspiration risk

• Take into account flow of normal secretions from mouth to stomach =

≈ 2–3 L/d or 100–150 mL/hr

• Clinically assess patient for abdominal distension, fullness, bloating, discomfort

If Gastric Residuals Limit Tube Feeding Delivery ?1-Place patient on his right side for 15–20

minutes before checking RV to avoid the cascade effect

2- Seek transpyloric access of feeding tube

3- Try using a prokinetic agent

4- Switch to a calorically dense product to decrease total volume needed

5- Tighten glucose control to <200mg% to avoid gastroparesis from hyperglycemia

6- Use narcotic alternatives

Enteral Nutrition Diets

Enteral Nutrition Diets1-Polymeric Formula

• Nitrogen source: whole protien

• CHO source: oligosaccharides-starch

• Fat source: vegetable oil.

• Minerals,vitamins,trace elements ---RDA

• A Standardized formulation provides

15-20% Pt, 30-40% Fat, 45-60% CHO

• Require some degree of digestion & absorption

• Isotonic ------ Caloric density 1Kcal/ml

Enteral Nutrition Diets2-Elemental (Monomeric & Oligomeric Formula)Chemically defined formulation• Nitrogen source: di/tripeptides, free a.aCan be absorbed by active transport without

intraluminal hydrolysis• CHO source: Oligosaccharides-glucose• Fat source: Medium Chain Triglycerides,

essential FA• Indicated --- Limited Digestive Capacity: intestinal fistula, radiation enteritis, short bowel

syndrome.

Enteral Nutrition DietsElemental Formula

• Are Fiber Free

• Due to multiple small particles, it is highly osmotic 500-900 mOsm/L

• Therefore ---Osmotic diarrhea

• No advantage in using elemental diet in pat with normal GIT

3-Special Formulas

1-Hepatic Failure Formulas:Decompensated Cirrhosis/Hepatic encephalopathy

Conc of AAA are and BCAA are .

• This imbalance ---- hepatic encephalopathy by producing false neurotransmitters

• BCAA-enriched and AAA-deficient nutrition formula ------- 45%-50% protien (BCAA)

• BCAA inhibit AAA from crossing BBB to

act as false neurotransmitters

2-Renal Failure Formulas:• CRF----- limited ability to excrete urea and

electrolytes

• Essential AA formula– To use urea for production of nonessential a.a -----reducing urea waste

• Hyperammonemia is a risk

• Polymeric Renal formula :low in protein (to limit urea production) – K – Mg - P

• Indicated for CRF who are not receiving dialysis

3-Pulmonary Formulas:• Metabolism of a calorie of CHO produces

more CO2 than the metabolism of a calorie of fat

• Low CHO --- CO2 load

• Modified CHO:Fat ratio , 40-55% calories are provided by fat.

• High fat feeds-----Delayed Gastric Emptying--Abd Distention----affect Diaphragmatic movement & Thoracic expansion

4-Gastrointestinal dysfunction Formulas• Gut recovery may be accelerated by

supplementation of glutamine and soluble fiber--a precursor SCFA.

• Glutamine and SCFA are metabolic fuels

of enterocytes and colonocytes

5- Metabolic Stress (Critical Care) Formula:• Provides exogenous source of BCAA-----

Preferred energy source for muscle during critical illness

• Not equivalent to Hepatic Failure formula

• High protein & not reduced in AAA content

• Not Given For Hepatic Failure

5-Immunomodulatory (immune enhancing) Formulas

5-Immunomodulatory (immune enhancing) Formulas:• Formulas---- Alter Body’s Response To

Critical Illness

• Modify the inflammatory response

• Enhance resistance to infection & wound healing

• Alteration include:Enrichment with specific a.a Glutamine/ArginineAddition of NucleotidesManipulation of FA content (n-6 to n-3 FA ratio)

Glutamine• Conditionally essential a.a.

• Primary Oxidative fuel for rapidly dividing cells -----Enterocytes- Lymphocytes- Macrophages

• ++ proliferation of T-cells & formation of ILs

• Precursor of Glutathione—Potent Antioxidant

• A substrate for DNA and RNA synthesis

• Maintains normal intestinal integrity

Glutamine

• Content in polymeric formula < 14% of total protein

• Optimum Provision is 20-30g/day to meet basal & GIT requirements in Critical Illness.

• Should be added to standard formula in: Burned & Trauma Patient Grade A recomend• Contraindicated in Liver Failure/Encephalopathy

ESPEN guidelines on Enteral nutrition 2007

Arginine

• Conditionally EAA

• Synthesis occurs --- Intestinal-Renal axis

Epith cells of SI-produce Citrulline from Glutamine

• Plays important role:

-Cell division (improves immune cell no. & func)

-Healing of wounds

-Ammonia detoxification

-Important secretagogue for insulin, glucagon, GH

Arginine

• Nitric Oxide donor to GI tract

– Necessary for normal immune function

– Helps kills bacteria/parasites

• Nitric Oxide can be detrimental

Mediates VDory effects of endotoxins------Controversy in cases of Septic Shock!!

What are the major problems associated with

tube feeding?

1- Aspiration----Most Important• Prevalence range from 2% - 95%

• Several issues should be considered:

1-Tube Size and Position

Large bore vs small bore

Gastric vs Jejunal

2-Body Position Supine vs Semi recumbent

3-Underlying Disease Gastroparesis/ Atony

4-Feeding Regimen

Intermittent or Continuous vs Bolus

To Limit the Risk of Aspiration

• 1- Raise head of bed 30-400 during feeding

and 1 hr after

• 2-Use intermittent / continuous feeding regimens rather than------ bolus method

• 3-Check gastric residual regularly

• 4-Consider jejunal access--------

-recurrent tube feeding aspiration

-high risk of gastric motility dysfunction

2-Diarrhea----Most Common• Incidence 2.3% - 68%• Critically ill are more prone • Multiple aetiologies:• 1-Medications:Antibiotics-----overgrowth of C.difficile / CandidaSorbitol base liquids---TheophyllineMeds containing Magnesium• 2-Altered bacterial floraH2-blockers/ PPI---permit bacterial overgrowthBacteria colonize---Gastric pH exceeds 4

2-Diarrhea----Most Common• 3-Formula Composition

Osmolality & Rate

incidence of diarrhea in critically ill

mechanically vent patients----receiving hyperosmolar feeds at high infusion rates

2-Diarrhea----Most Common

• 4-Hypoalbuminemia

---Reduces osmotic pr & causes intestinal mucosal oedema

Critically ill with s.Alb < 2.6g/dl diarrhea with standard EN

• 5-Formula Contamination

Altered Drug absorption & Metabolism

• PhenytoinBinds to NG tubing at pH of enteral

formulation----less drug delivery

• WarfarinResistance 2ndry to Vit K in Enteral feedings

Stop enteral feeding 2 hrs before and 2 hrs after

Metabolic Complications• Less frequent compared to TPN

• Hyperglycemia: 2ndry to High CHO load in specific formula esp critically ill / elderly--------insulin resistance

• Electrolyte imbalance:

Use of high osmolar formulation esp: Pat on fluid restriction/ renal concentrating difficulties are at risk of

-----Dehydration & Hypernatremia

Mechanical Complications

Tube clogging First line is to instill warm water using

slight manual pressure. If fails, Pancreatic enzyme tablet crushed

with Na HCO3 tablet dissolved in 5ml of water in order to "digest" the clog