Enteral Nutrition In
Critically Ill
Rasha S.Bondok
M.D.
Anaesthesia & Intensive Care
Ain-Shams University
Enteral Nutrition
Terminology
Enteral 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 & Trauma
Skeletal muscle
Protein breakdown
Amino
Acids
Liver
Glucose
Amino acids
Glucose Synthesis
Lactate from tissues
Adipose tissue
Glycerol
Triglyceride
Glycerol & FFA
FFA
Sepsis
Skeletal muscle
Protein breakdown
Amino
Acids
Liver
Glucose
Glycogen
Amino acids
Glucose Synthesis
Ketone
Bodies
Lactate from tissues
FFA
Adipose tissue
Glycerol
Triglyceride
Glycerol & FFA
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
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 malnourished
83.5 - 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
• Intestinal dysmotility
Are Not
Contraindications
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)
Quiz
What length of small bowel
is necessary to maintain
adequate Enteral Nutritional
Status?
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 atony
for 1-2 days but small bowel
motility 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 feeding
Fine bore 8-10 F NG tubes
Access Techniques…..cont
Nasojejunal 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 cancer
Gastric ulcer
Ascitis
Coagulation 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 syringe
Indications:
-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% (690820)
 1.5-2.0 kcal/mL = 69% - 72% (690720)
 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 EnterallyFed 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 Diets
1-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 Diets
2-Elemental (Monomeric & Oligomeric Formula)
Chemically defined formulation
• Nitrogen source: di/tripeptides, free a.a
Can 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 Diets
Elemental 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/Arginine
Addition of Nucleotides
Manipulation 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
0
• 1- Raise head of bed 30-40 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 / Candida
Sorbitol base liquids---Theophylline
Meds containing Magnesium
• 2-Altered bacterial flora
H2-blockers/ PPI---permit bacterial overgrowth
Bacteria 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
• Phenytoin
Binds to NG tubing at pH of enteral
formulation----less drug delivery
• Warfarin
Resistance 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