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Nutrition in the ICU
Rachel Garvin, MDOctober 24, 2014
How Much do I need?O 56 yo F admitted to the ICU after a
MVCO h/o DM, HTN, HLD, OAO She suffered a TBI, multiple rib
fractures, PTX, tib-fib fx, splenic lacO Intubated on MVO HD#3 develops fevers to 103O BMI is 45
Goals of PresentationO Why is nutrition importantO Calculating nutritional needsO Enteral vs ParenteralO Gastric vs Post-pyloricO FormulasO ResidualsO Probiotics
Energy UseO Initially when body not getting enough
total nutrients fat used more the proteinO Glucose stores used up (small amounts of
glucose needed for fat metabolism)O Amino acids then needed for
gluconeogenesis so lean body mass then lost
O This becomes problematic in patients who are nutritionally deplete prior to hospitalization
Revved up systems
O In critically ill patients, body moves into a hypercatabolic stateOStress response
O In recovery, patients move into a hyperanabolic stateONeed substrate to build back
up
HypermetabolismO Metabolic rate increases 120-250%
in brain injured patients (even when sedated)
O SIRS-type response causing catecholamine surge; catabolic hormones surge
O Increased needs for:O ProteinO LipidsO Carbs
Hypermetabolic StateO Increased Stress Increased
Catecholamines increases lipolysis and gluconeogenesis
O Increased Stress Increased Cortisol Increased lipolysis and proteolysis
Hyperglycemia
What is Malnutrition
OAltered intake of macro and micronutrients
OCan lead to:OOrgan dysfunctionOBiochemical abnormalitiesOBody mass index loss as lean
body mass is catabolizedOImmune dysfunction
How do we measure nutritional status?
O Ideal body weightO BMI
O Measure of body fat based on weight, height
O Plasma proteins: need to compare with positive APRO Albumin – ½ life 2 weeksO Prealbumin – ½ life 2 daysO Retinol binding protein – ½ life 12 hrsO Transferrin
Nutritionally High RiskO Increasing disease severityO Pre-existing nutritional statusO Low BMI or recent weight lossO Prolonged LOS
How do we know what our patient’s need?
O First – calculate total fluid requirementO 20-40ml/kg day
O Second – total energy requirementO Most straightforward: 25-30kcal/kg/dayO Metabolic cart O Harris-Benedict Equation = REE
(overestimates)O Brain requires 20% of REE
O Clifton EquationO 152-[14 x GCS] = 0.4 x HR + 7 x day since
injury
Harris-Benedict Equation
REE = basal metabolic rate REE x CF
Women: REE = 655 + (9.6 X weight in kg) + (1.7 X height in cm) - (4.7 X age in years)
Men: REE = 66 + (13.7 X weight in kg) + (5.0 X height in cm) - (6.8 X age in years)
Calorie requirements/day =
CF X REE (for each 1°C above
37 add 10% extra allowance
O Correction factors:O Post-op: 1.1-1.5O Sepsis: 1.3O Multi-trauma:
1.5-1.6O Burns: 1.5-2
Metabolic Cart
OMeasures VO2 (consumption) and VCO2 over 10-30 minutes
OFor accuracy, need intubated patient at low FiO2 who is calm
OCan’t have any air leaksODialysis can affect
Special SituationsO Sepsis
O Significant catabolic stateO Higher protein requirement
O Respiratory FailureO RQ (CO2 production/O2
consumption)O Renal FailureO Liver FailureO Extremes of BMI (<20 or >40)
Obese PatientsO Often fed later and inappropriatelyO Increase protein (2-2.5g/kg/IBW)O Decrease total requirement (65-70%
of caloric requirement)
Nitrogen Balance
Urinary nitrogen balanceOEach gram of nitrogen
produced requires 100-150kcalOPatients with severe TBI who
are not fed can lose up to 25g nitrogen/day
OResult is loss of up to 10% lean body mass in 1 week
Where are nutrients absorbed?
OMost nutrients are absorbed in the small intestines
OWater is absorbed in the stomach and colon
OVit K, Na+, Cl-, K+ and short chain FA’s are absorbed in colon
BasicsO Carbs
O 30-70%O Provides 4kcal/g
O FatO 20-50%O Provides 9kcal/g
O ProteinO 15-20%O Provides 4kcal/g
Enteral Nutrition
Data Behind ENO EN within first 24-48 hours reduce
infection, LOS and mortalityO Delay of EN or interruption of feeding
produce significant calorie deficitO Nurse driven protocols show earlier
initiation of nutrition and decreased mortality
Enteral vs Parenteral
OEnteral is preferred routeOPreserves GI barrierOMaintains integrity of intestinal
villiOReduces gut bacterial
translocationO Increased uptake of glutamine
despite decreased intake
Gastric vs. Post-pyloricO Gastric feeds (especially bolus) simulate normal
intakeO Gastric feeding allows body to regulate transition of
food to duodenum and insulin releaseO Gastric feeding allows better regulation of gastric
pHO Gastric is preferred unless:
O Patient unable to sit >30 degreesO IleusO Residuals >500
O Post-pyloricO Need slower titration of rates to prevent dumping
syndrome
Trophic vs Full Feeds?O Study of ARDS pts showed no
difference in oucomes in trophic (25% of calories) vs full feeds
O Trophic feeds for up to 6 days does not show harm (select patient populations)
Choosing an Enteral Formula
O Formulas with arginine, fish oil and nucleotides are helpful in elective surgery pts
O Anti-inflammatory lipids and omega-3s helpful in ARDS
TPNO Consider parenteral nutrition if patient unable to
tolerate enteral feeds by day 7O Need dedicated lineO Dextrose is major source of caloriesO Lipids provide essential FA’s
O Max administration of 5-7g/kg/dayO Amino AcidsO Additives
O ElectrolytesO VitaminsO Trace elementsO Insulin
TPN Calculators
Tube Feed FormulasFibersource HN: standard high protein with
fiber. 1.2kcal/mlReplete: 1.0kcal/ml. Higher protein than
fibersourceImpact peptide: 1.5kcal/ml. Concentrated
caloriesRenal Formulas: 2.0kcal/ml, lower levels of K+
and phosOxepa: low carb, high proteinPeptamen: monomeric, predigested formula
Fluid RequirementO 20-40ml/kg or 1ml/kcalO Most tube feed formulas are 70- 80%
free waterO Example: 70kg patient with large
amount of insensible lossesO 40ml/kg x 70kg = 2800ml fluid
requirementO Getting tube feeds at 70ml/hr =
1680ml/day of which 1344 is free H2O
ProbioticsO Competitive inhibition of pathogensO Stimulate physical gut barrier and
mucous productionO Reduce adherence and attachment
of pathogensO Produce proteins that bind
pathogensO Stimulate T-cell production and
increased secretory IgA
What about GlutamineOUsed for hepatic urea synthesisORenal ammoniagenesisOGluconeogenesisORespiratory fuel for cellsOPrecursor for glutamate, excitatory
neurotransmitter increased seizure risk
OAlso produces glutathione, a potent anti-oxidant
Feeding on Pressors
Residuals
OSlowed gastric motility – up to 50% of mechanically ventilated patients
OStopping feeds based on GRV?
Gastric ResidualsO Compare effects of increasing GRV
from 200500mlO Randomized 329 patientsO GRV measured every 8 hours on EN
day #2 and then dailyO Reglan given to all pts during first 3
days of EN
Gastric ResidualsO Gastrointestinal complications:
O Abdominal distentionO High GRV: 200 vs 500mlO VomitingO DiarrheaO Aspiration
Gastric ResidualsO Incidence of complications higher in
the control groupO Diet volume ratio similar in both
groups (diet received/diet prescribed)
SummaryONutrition is vitally important in ICU
patientsOUnderstand the nutritional needs of
your patientsOCalculate requirement and/or get a
nutrition consultOUse the gut whenever possibleONutrition should commence by day 3
and not later than day 7