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NUTRITION IN ICU
DR. MUNIRA DILAWER GHEEWALA
NUTRITION - THE ENERGY FUEL
OXIDATIVE METABOLISM : The process by
which the body derives energy from nutrient
fuels and uses it to sustain life.
 A process which consumes oxygen and
generates carbon dioxide, water and heat.
 3 main nutrient fuels- carbohydrates , proteins
and lipids.
 Lipids have the highest energy yield (9.1
kcal/gm) while glucose has the lowest (3.7
kcal/gm)

CARBOHYDRATES
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The hydrated carbon that acts as a ready
source of energy.
Provide 60-70% of non-protein calories
Glucose- primary source of fuel for the Brain
Provides energy for Immune function, Red
blood cells, Bone marrow and Wound healing
In Critical illness – excess administration causes
hyperglycaemia (peripheral tissue resistance to
insulin and increased gluconeogenesis with
increase in counterregulatory hormones)
THE CARBOHYDRATE IMBALANCE
IN CRITICAL ILLNESS – excess exogenous
carbohydrate administration can cause
hyperglycaemia
 Hyperglycaemia – deleterious effects on
outcomes in critically ill patients.
 The carbohydrate norm in critical illness
1. 50-60 % of non protein calories
2. Administered at 5 ml/kg/min
3. Tight blood glucose control

PROTEINS
FUNCTIONS:
1. Gluconeogenesis
2. Thermogenesis
3. Immune function
4. Tissue repair
5. Enzymatic function
6. Acute phase protein synthesis
 In critical illness – protein loss is accelerated
due to hypercatabolism and proteolysis.

PROTEIN BALANCE
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Normal protein intake is 0.8 -1.0 gm/kg
In ICU patients – 1.2-1.5 gm/kg of daily protein
intake is recommended.
Nitrogen excretion – 2/3 rd of nitrogen derived
from protein breakdown is excreted
Nitrogen Intake = Protein Intake/6.25
Nitrogen Balance – the diff between nitrogen
intake and excretion.
Positive Nitrogen Balance of 4-6 grams is
recommended.
LIPIDS

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Highest energy yield of the nutrient fuels
Form approx 30 % of the daily energy needs
Adipose Tissue –major reserve of endogenous
fuel source in healthy adults.
Linoleic Acid – only dietary fatty acid
considered essential that needs to be provided
in food – poly unsaturated fatty acid.
In Critical illness – lipolysis of fats increases due
to adrenergic stimulation from stress.
THE LIPID BIOLOGY
Contribution of Fat oxidation to energy
production is increased in critically ill patients.
 Fatty acids liberated by lipolysis – primary
source of ATP during stress.
 Approx 40 -50 % of non protein calories in
Critically ill patients should be from fats.
 Propofol – available as 10% lipid emulsion.
when used in ICU the calorie provided by it
should be taken into consideration –1.1 kcal/ml.

THE 13 – ESSENTIAL VITAMINS
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Vit A – helps maintain healthy skin, teeth, bones
and soft tissue, cell growth and night vision.
Vit C – Antioxidant and collagen synthesis.
Vit D – Calcium metabolism and aids in Bone
formation
Vit E – Formation of RBC’s and as antioxidant
Vit K – Blood coagulation
Vit B1 – Thiamine – Thiamine pyrophosphate
(coenzyme) required for carbohydrate
metabolism and ATP production.
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Vit B2 – Riboflavin – growth and production of
RBC’s. (oxidative phosphorylation)
Vit B3 – Niacin – part of NAD, redox reactions.
Vit B5 – Pantothenic Acid –part of Coenzyme A
Vit B6 – Pyridoxine – helps to make antibodies
and helps maintain nerves and blood sugar, part
of decarboxylase activity.
Vit B7 – Biotin – Carboxylase activity.
Vit B9 – Folic Acid – Tissue growth and cell
function and RBC maturation.
Vit B12 – Formation of RBC and in metabolism.
THE MINERAL POOL – TRACE ELEMENTS
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SELENIUM – Antioxidant prop, Fat metabolism.
ZINC – Energy metabolism, Protein synthesis
and Epithelial growth.
COPPER – Collagen Cross linking and
Ceruloplasmin activity.
MANGANESE – Neural function and Fatty acid
synthesis.
CHROMIUM – Insulin activity.
COBALT – Vit B12 Synthesis.
IODINE – Thyroid hormone synthesis.
CONTD…
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IRON – Haematopoiesis and oxidative
phosphorylation.
MOLYBDENUM – Purine and Pyrimidine
metabolism.
CALCIUM – Bone formation, clotting factor,
other cellular functions.
MAGNESIUM – Ca and PO4 regulation , cardiac
contractility, smooth muscle relaxation.
PHOSPHORUS – ATP formation, Bone
formation and DNA synthesis.
MALNUTRITION IN THE ICU
Malnutrition - from starvation – is due to
depletion of essential nutrients.
 Malnutrition - from critical illness - due to
abnormal nutrient processing.
 In ICU both type of patients may be present but
the second one is more commoner.
 Malnutrition could also be due to “excess” of
proteins, energy, vitamins or minerals.

EFFECTS OF MALNUTRITION
1. LOSS OF BODY CELL MASS
2. DERANGEMENT OF ORGAN
SYSTEM FUNCTIONS
3. IMPAIRED IMMUNE
FUNCTION
4. PROLONGED MECHANICAL
VENTILATOR DEPENDANCE
5. INCREASED RATES OF
INFECTION
6. PROLONGED LENGTH OF
STAY
7. GREATER PATIENT
MORBIDITY AND MORTALITY.
GOAL OF APPROPRIATE
NUTRITION IN ICU
TO GIVE THE RIGHT FEED IN THE RIGHT AMOUNT
AND COMPOSITION AT THE RIGHT TIME VIA
THE RIGHT ROUTE
THE RIGHT FEED
SOLID v/s SOFT v/s LIQUID v/s NBM
 In most awake alert patients – solid full diet or
soft diet is well tolerated per orally except
when there is evidence of INTESTINAL
OBSTRUCTION or PERFORATION or
GASTROPARESIS
 In Mechanically Ventilated patients , Pancreatitis
and other conditions associated with Abdominal
or Respiratory Discomfort – Liquid feeds are
better accepted.
 Patient tolerance of Feed should be
individualised.

THE RIGHT AMOUNT AND COMPOSITION
STEP 1: NUTRITIONAL ASSESSMENT
A. Clinical Assessment :
1. WEIGHT HISTORY – Baseline weight on
admission or estimated loss of weight in the
past months.
Weight loss of >5% in 1month or >10% in 6
months – poor prognostic indicator(except
rapid fluid shifts in past few days)
If the weight and height can be measured –
Body mass index can be calculated =
weight/(height in metre)*2

CONTD..
BMI <18.5 = UNDERWEIGHT
BMI >25 = OVERWEIGHT
BMI >30 = OBESE
BMI >39 = MORBIDLY OBESE
 Most critical patients do not allow weight and
height measurement
 Body composition measurement = Bioelectrical
Impedance Analysis – gives estimate of TBW , free
fat mass , body fat and body cell mass. (cannot
determine short term nutritional changes and
inappropriate in renal dysfunction and gross
edema)
CONTD..
2. CLINICAL HISTORY AND PHYSICAL
ASSESSMENT:
i.
Abnormalities of Skin and Mucous Membranes
ii. Decubitus Ulcers
iii. Diabetic Ulcers
iv. Muscle Wasting
v. Generalised Edema
vi. Stigmata of Steroid Use
 3. BOWEL FUNCTION : rule out Constipation ,
Diarrhoea , Paralytic Ileus (surgical, functional,
pharmacological), Emesis, Gastrointestinal
Bleeding, Hemodynamic Instability and
Mechanical Ventilation.

CONTD..
4. INJURY AND ILLNESS TYPE & SEVERITY
i.
Cirrhosis or Chronic Liver Disease
ii. Chronic Renal Dysfunction
iii. Malignancy
iv. Congestive Heart Failure
v. Burns
vi. Sepsis or SIRS
vii. Major Trauma
viii. Uncontrolled Diabetes
ix. Chronic Obstructive Pulmonary Disease
x. Immunosuppressed states

CONTD..
Assessment in these critical illness states is crucial
because of greater catabolic breakdown of
proteins and fats and increased gluconeogenesis to
provide for increased metabolic requirements of
the body.
 Inflammatory markers released in Sepsis add to
the metabolic alterations.
 Hormonal release of Glucagon, Catecholamine's,
Cortisol and Insulin in stress states contribute.
B. Laboratory Assessment :
Measurement of Total Proteins , Serum Albumin,
Prealbumin and Transferrin, Renal Profile and
Vitamin and Macronutrient levels.

STEP 2: NUTRITIONAL REQUIREMENTS
ENERGY REQUIREMENTS
 BASAL ENERGY EXPENDITURE: Energy
expended by body in resting state under basal
conditions, varying with weight and function of
body surface area.
Given by Harris-Benedict Equation:
Other equations: Ireton Jones eqtn, Frankenfield and
Penn state eqtn, Swinamer eqtn = Cumbersome
and Complicated with no adjustment for activity
and stress.
RESTING ENERGY EXPENDITURE
INDIRECT CALORIMETRY = most accurate
method but requires trained personnel with
expensive equipment and is not universally
available.
REE(kcal/min) = (3.6xVO2) + (1.1 x VCo2) – 61
THE SIMPLER ESTIMATES
 Resting Energy Expenditure = 25 x Body weight
(kg)
 Weight based estimates: total energy provision of
25-35 kcal/kg/day with adjusted body weight
Adjusted weight(kg) = {(Actual-Ideal)weight x 0.25}
+ Ideal Body weight
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Ideal body weight. Males: IBW = 50 kg + 2.3 kg
for each inch over 5 feet.
Females: IBW = 45.5 kg + 2.3 kg for each inch
over 5 feet.
PROTEIN REQUIREMENTS
GOAL – To provide protein to make up for
protein catabolism and sufficient for anabolism in
cases of muscle wasting.
2. Most ICU patients – 1.5-2.0 g/kg/day
sufficient to keep a positive nitrogen balance of
4-6 g/day
1.
CONTD..
3. Patients with ARF not dialyzed – 0.5-0.8 g/kg/day
4. Patients with ARF or CRF on Hemodialysis – 1.2
g/kg/day
5. Patients on CRRT – 1.5-2.5 g/kg/day
Titrate @ change in Blood Urea Nitrogen levels and
Nitrogen balance
6. Nitrogen Balance = Protein intake (g/day) / 6.25 –
Urine Urea Nitrogen (g/day) – 4 g/day.
FLUID & ELECTROLYTE REQUIREMENTS
Fluid Requirement : Goal - maintain adequate
urine output & balance serum electrolyte
concentrations.
Individualised to patient requirement.
 Electrolyte Requirement : Individualised to patient
requirement. Goal - maintain adequate serum
concentrations.
 Vitamin and Trace Element requirements : Goal supplement enough to optimize the use of
macronutrients and support the integrity of the
body’s defence’s.
Each micronutrient is administered in a dose to
meet the recommended dietary allowance.

REMEMBER
AVOID OVERFEEDING AS
MUCH AS YOU AVOID
UNDERFEEDING
THE RIGHT TIME
Feeding should be initiated as early as 24-48 hours
in most critically ill patients from the time of
admission to the ICU.
THE RIGHT ROUTE
ENTERAL V/S PARENTERAL – THE GREAT
DEBATE
 Enteral Nutrition is indicated in all cases except its
contraindications…
 …and they are the Indications for Parenteral
Nutrition.
 Unless the patient needs to be kept starved for
short period of time (<24 hours) , starting of
nutrition via any route feasible is absolutely
indicated.
 Presence of bowel sounds is not essential to
initiate enteral tube feedings.

CONTRAINDICATIONS TO ENTERAL
NUTRTION
Gastro-intestinal : severe diarrhoea or intractable
vomiting , paralytic ileus, intestinal obstruction,
severe GI bleeding, acute pancreatitis and high
output external fistula, intestinal ischemia or
infarct.
 Cardiac : Hemodynamic instability, low cardiac
output, circulatory shock.
 Lack of Access : unobtainable safe access to GIT.
 Failed enteral trials with post-pyloric tube placement.

BENEFITS OF ENTERAL FEEDING
The major
advantage over
Parenteral
nutrition is
prevention of
infectious
complications.
Trophic effects
of the
nutritional bulk
maintain the
barrier and
immunological
functions of the
bowel.
THE PREVENTIVE MECHANISM
Presence of food or tube feed in the lumen of the
bowel exert a trophic influence on the bowel
mucosa – structural integrity of the mucosa –
barrier function – prevents translocation.
 Production of Immunoglobulin A by monocytes.
 Gastrin and Cholecystokinin & other nutrients
present in the bowel lumen – especially Glutamine
also contribute.
 Effects are lost during periods of bowel rest –
atrophy of bowel mucosa – translocation and
systemic spread of enteric pathogens.

THE ENTERAL FEEDING FORMULAS
Around 200 feeding formulas are commercially
available. (Osmolite , Osmolite HN, Isocal HCN)
 Caloric Density – 1/1.5/2 kcal/ml available
High calorie formulas (2 kcal/ml) used for severe
physiological stress like multisystem trauma and
burns and most commonly when volume
restriction is a priority.
 Non protein calories of around 85%
 Osmolality of 280-300 mosmol/kg H2O with
caloric density of 1kcal/ml and those with 2
kcal/ml have that twice that of the plasma.
 Protein content – 35-40 gm/L

CONTD..
Proteins in the feeding formulations may be intact
proteins (polymeric formulas) , small peptides
(semi-elemental formulas) and individual aminoacids (elemental formulas).
 Elemental proteins are more readily absorbed than
intact proteins & preferred in pts with diarrhoea.
 High protein formulas are designated as HN –high
nitrogen.
 Carbohydrate Content – 40-70% of the total
calories.
Low Carbohydrate content (30-40%) formulas –
available for diabetics.
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CONTD..

Fiber content – mixture of fermentable and non
fermentable varieties - promote viability of
surface of the large bowel(F) and also draw and
increase water content of the stool (NF).
 Lipid Content – PUFA - 30 % of total calories –
influence inflammatory response - especially
omega 3 fatty acids – immunonutrition.

Conditionally Essential Nutrients – Arginine
and Carnitine
Arginine – 1. Promotes wound healing
2. Precursor of nitric oxide
Preferred in polytrauma and post-operative patients
but can worsen sepsis.
CONTD..

Carnitine – Transport of fatty acids for fatty acid
oxidation
Carnitine deficiency – myopathy involving heart
and skeletal muscle.
RDA – 20-30 mg/kg in adults.
CREATING A FEEDING FORMULA
1.
2.
3.
4.
a.
b.
Estimate daily calorie and protein requirements
Calories (kcal/day) = 25 x wt(kg)
Protein (g/day) = (1.2-1.6) x wt (kg)
Select Feeding Formula
Calculate desired infusion rate.
Feeding volume (ml) = Kcal/day required
Kcal/ml in feeding formula
Infusion rate (ml/hr) = Feeding Volume (ml)
Feeding time (hrs)
Adjust Protein Intake if necessary:
Calculate Protein Intake
Adjust protein to the feeding regime if less.
ADVANCING THE TIP OF THE FEEDING TUBE
INTO THE DUODENUM IS CONSIDERED OF
NO ADDED BENEFIT IN PREVENTING
ASPIRATION OF GASTRIC CONTENTS AS
EARLIER THOUGHT.
GASTRIC RESIDUAL VOLUMES
A BRIEF OVERVIEW
Residual volumes of up to 500 ml still do not
increase the risk of Aspiration Pneumonia.
 To continue feeding until GRV > 500 ml
 To return the GRV back through the tube
and hold feeding for 1-2 hrs if GRV >400 ml
 Look for other signs of intolerance of feed
except GRV – vomiting, bloating, patient
discomfort.
 Gastro paresis : the major culprit.
 Start Low .. Go Slow. (to achieve target
feeding in 72 hrs)

MEASURES TO PROMOTE INTESTINAL
MOTILITY
 Head end of the bed Propped up >45 degrees
 Advance feeding tube into small bowel
(controversial)
 Prokinetic agents :
1. Metoclopramide 10 mg iv every hrly
2. Erythromycin 200 mg iv every 12 hrly
3. Enteral Naloxone 8 mg via Nasogastric tube
every 6 hrly
For intolerant patients – Consider starting TPN.
PARENTERAL NUTRITION
1.
A.
B.
2.
A.
GUIDELINE RECOMMENDATIONS
INDICATIONS :
Patients should be fed because underfeeding is
associated with increased morbidity and
mortality.
TPN should be started within 24-48 hrs of ICU
admission if EN is contraindicated or cannot be
tolerated.
REQUIREMENTS :
TPN should be a complete formulation to cover
the patient needs fully.
CONTD..
B.
C.
3.
A.
B.
In acute illness, provide energy according to
measured energy expenditure and to decrease
negative energy balance.
In absence of indirect calorimetry , target initial
energy at 25 kcal/kg/day – to increase over 2-3
days.
SUPPLEMENTARY PN WITH EN
CARBOHYDRATES :
If EN is less than that required for >48 hrs,
supplement with PN.
Minimum Carbohydrate required is 2 g/kg of
glucose per day.
CONTD..
C.
4.
A.
B.
C.
D.
Hyperglycaemia (BSL > 10 mmol/L) should be
avoided – increased mortality and morbidity in
critically ill patients.
LIPIDS :
Integral part of PN to provide essential fatty acids
in long term ICU patients.
IV lipid emulsion administered at rate of
0.7-1.5 g/kg over 12-24 hrs.
Olive oil based preparation is well tolerated in
critically ill patients.
Fish- oil enriched preparations decrease ICU
length of stay.
CONTD..
5.
A.
B.
6.
7.
A.
PROTEINS:
Amino acids should be infused at the rate of 1.31.5 g /kg (ideal body weight)/day with adequate
energy supply.
Amino Acid solution should contain 0.2-0.4 g /kg
of t-glutamine per day.
MICRONUTRIENTS :
Daily dose of multivitamins and trace elements
should be included.
ROUTE :
Central Venous Access is mandatory to deliver
high osmolar TPN solutions
CONTD..
Peripheral Venous Access - Designated for low
osmolality solutions (<850 mosmol/L).
8. MODE :
TPN should be administered in a all-in-one-bag
solution.
B.
COMPLICATIONS OF TPN
Catheter related Sepsis and other complications
of Central Venous Access.
 Electrolyte Abnormalities – Hypokalemia ,
Hypophosphatemia and Hypomagnesemia in first
24-48 hrs.
 Hyperchloremic Metabolic Acidosis – Amino Acid
solutions with a high chloride content. (Replace
chloride with acetate)
 Rebound Hypoglycaemia – when TPN is
discontinued suddenly – slow weaning over 12
hours is recommended.

(If necessary Dextrose solutions should be started if TPN
is to be discontinued)
Liver dysfunction - hepatic steatosis, intrahepatic
cholestasis and biliary sludging from gallbladder
inactivity.
Pre-existing liver dysfunction may worsen
 Deficiencies of trace elements and vitamins
(especially Thiamine, folic acid and vitamin K)
 REFEEDING SYNDROME : occurs when normal
intake is resumed after prolonged starvation.

Associated with profound hypokalemia , hypomagnesemia
and hypophosphatemia.
When glucose is restored as a substrate – insulin is
released and causes cellular uptake of these ions.
It can lead to cardio respiratory failure, paresthesia and
seizures. Thiamine deficiency can contribute.