Nutrition in the ICU Rachel Garvin, MD October 24, 2014.

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