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

2. How Much do I need? 56 yo F admitted to the ICU after a MVC
h/o DM, HTN, HLD, OA
She suffered a TBI, multiple rib fractures, PTX, tib-fib fx, splenic lac
Intubated on MV
HD#3 develops fevers to 103
BMI is 45

3. Goals of Presentation Why is nutrition important
Calculating nutritional needs
Enteral vs Parenteral
Gastric vs Post-pyloric
Formulas
Residuals
Probiotics

4. Energy Use
Initially when body not getting enough total nutrients  fat used more the protein
Glucose stores used up (small amounts of glucose needed for fat metabolism)
Amino acids then needed for gluconeogenesis so lean body mass then lost
This becomes problematic in patients who are nutritionally deplete prior to hospitalization

5. Revved up systems
In critically ill patients, body moves into a hypercatabolic state
Stress response
In recovery, patients move into a hyperanabolic state
Need substrate to build back up

6. Hypermetabolism
Metabolic rate increases % in brain injured patients (even when sedated)
SIRS-type response causing catecholamine surge; catabolic hormones surge
Increased needs for:
Protein
Lipids
Carbs
Catabolic hormones: cortisol, glucagon,

7. Hypermetabolic State
Increased Stress  Increased Catecholamines  increases lipolysis and gluconeogenesis
Increased Stress  Increased Cortisol  Increased lipolysis and proteolysis

8. Hyperglycemia

9. What is Malnutrition Altered intake of macro and micronutrients
Can lead to:
Organ dysfunction
Biochemical abnormalities
Body mass index loss as lean body mass is catabolized
Immune dysfunction

10. How do we measure nutritional status?
Ideal body weight
BMI
Measure of body fat based on weight, height
Plasma proteins: need to compare with positive APR
Albumin – ½ life 2 weeks
Prealbumin – ½ life 2 days
Retinol binding protein – ½ life 12 hrs
Transferrin

11. Nutritionally High Risk
Increasing disease severity
Pre-existing nutritional status
Low BMI or recent weight loss
Prolonged LOS

12. How do we know what our patient’s need?
First – calculate total fluid requirement
20-40ml/kg day
Second – total energy requirement
Most straightforward: 25-30kcal/kg/day
Metabolic cart
Harris-Benedict Equation = REE (overestimates)
Brain requires 20% of REE
Clifton Equation
152-[14 x GCS] = 0.4 x HR + 7 x day since injury
Fluid requirements increase: 12% with each degree of fever, 25% for sweating, 60% for hyperventilation
The lower the GCS, the more kcal/day your patient needs: 30kcal/day for mild TBI up to 45kcal/day for severe TBI
Metabolic Cart (indirect calorimtery) measures REE through Vo2 and CO2 prodction. Each liter of O2 consumed is equivalent to 5 kcal

13. Harris-Benedict Equation
REE = basal metabolic rate
REE x CF
Women: REE = (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
Correction factors:
Post-op:
Sepsis: 1.3
Multi-trauma:
Burns:

15. Metabolic Cart Measures VO2 (consumption) and VCO2 over 10-30 minutes
For accuracy, need intubated patient at low FiO2 who is calm
Can’t have any air leaks
Dialysis can affect
Shown to be most helpful in those at extremes of BMI

16. Special Situations Sepsis Significant catabolic state
Higher protein requirement
Respiratory Failure
RQ (CO2 production/O2 consumption)
Renal Failure
Liver Failure
Extremes of BMI (<20 or >40)
Glucose metabolism R/Q 1.0 (above normal of 0.85) – overfeeding can be problematic with respiratory distress  increase CO2 production

17. Obese Patients Often fed later and inappropriately
Increase protein (2-2.5g/kg/IBW)
Decrease total requirement (65-70% of caloric requirement)
Based on small RCTs ad retrospective cohort studies

18. Nitrogen Balance Urinary nitrogen balance
Each gram of nitrogen produced requires kcal
Patients with severe TBI who are not fed can lose up to 25g nitrogen/day
Result is loss of up to 10% lean body mass in 1 week

19. Where are nutrients absorbed?
Most nutrients are absorbed in the small intestines
Water is absorbed in the stomach and colon
Vit K, Na+, Cl-, K+ and short chain FA’s are absorbed in colon

20. Basics Carbs 30-70% Provides 4kcal/g Fat 20-50% Provides 9kcal/g
Protein
15-20%

22. Enteral Nutrition

23. Data Behind EN
EN within first hours reduce infection, LOS and mortality
Delay of EN or interruption of feeding produce significant calorie deficit
Nurse driven protocols show earlier initiation of nutrition and decreased mortality
Nurse driven protocols based on prospective data

25. Enteral vs Parenteral Enteral is preferred route Preserves GI barrier
Maintains integrity of intestinal villi
Reduces gut bacterial translocation
Increased uptake of glutamine despite decreased intake
Glutamine is most abundant AA in blood (precursor for purines/pyrimidines) and enterocytes use it as primary fuel source

26. Gastric vs. Post-pyloric
Gastric feeds (especially bolus) simulate normal intake
Gastric feeding allows body to regulate transition of food to duodenum and insulin release
Gastric feeding allows better regulation of gastric pH
Gastric is preferred unless:
Patient unable to sit >30 degrees
Ileus
Residuals >500
Post-pyloric
Need slower titration of rates to prevent dumping syndrome
Decreased risk of aspiration with post-pyloric feeding but does not translate into lower rate of PNA, longth on MV, ICU LOS or mortality

27. Trophic vs Full Feeds?
Study of ARDS pts showed no difference in oucomes in trophic (25% of calories) vs full feeds
Trophic feeds for up to 6 days does not show harm (select patient populations)
No surgical patients, most patients with BMI> 30 and excluded malnourished pts.

28. Feeding algorithm based on CHEST 2014 guidelines

29. Choosing an Enteral Formula
Formulas with arginine, fish oil and nucleotides are helpful in elective surgery pts
Anti-inflammatory lipids and omega-3s helpful in ARDS

30. TPN
Consider parenteral nutrition if patient unable to tolerate enteral feeds by day 7
Need dedicated line
Dextrose is major source of calories
Lipids provide essential FA’s
Max administration of 5-7g/kg/day
Amino Acids
Additives
Electrolytes
Vitamins
Trace elements
Insulin

31. TPN Calculators

32. Tube Feed Formulas
Fibersource HN: standard high protein with fiber. 1.2kcal/ml Replete: 1.0kcal/ml. Higher protein than fibersource Impact peptide: 1.5kcal/ml. Concentrated calories Renal Formulas: 2.0kcal/ml, lower levels of K+ and phos Oxepa: low carb, high protein Peptamen: monomeric, predigested formula

33. Fluid Requirement 20-40ml/kg or 1ml/kcal
Most tube feed formulas are % free water
Example: 70kg patient with large amount of insensible losses
40ml/kg x 70kg = 2800ml fluid requirement
Getting tube feeds at 70ml/hr = 1680ml/day of which 1344 is free H2O

34. Probiotics Competitive inhibition of pathogens
Stimulate physical gut barrier and mucous production
Reduce adherence and attachment of pathogens
Produce proteins that bind pathogens
Stimulate T-cell production and increased secretory IgA
Pathogens: pseudomonas, staph, enteroinvasive e.coli
Works in the colon not SI

35. What about Glutamine Used for hepatic urea synthesis
Renal ammoniagenesis
Gluconeogenesis
Respiratory fuel for cells
Precursor for glutamate, excitatory neurotransmitter  increased seizure risk
Also produces glutathione, a potent anti-oxidant
Thought to be an essential additive but later study showed risk of increased mortality

36. Feeding on Pressors
Prospective study 1174 medical pts requiring MV >2 days and pressor support (amt not noted). Early (within 48 hours) vs late EN.
Both ICU and hospital mortality reduced even when adjustments made for confounding.

37. Residuals
Slowed gastric motility – up to 50% of mechanically ventilated patients
Stopping feeds based on GRV?

38. Gastric Residuals Compare effects of increasing GRV from 200500ml
Randomized 329 patients
GRV measured every 8 hours on EN day #2 and then daily
Reglan given to all pts during first 3 days of EN
Study by Montejo et al ICM 2010
Reglan dose 10mg q8 hours

39. Gastric Residuals Gastrointestinal complications: Abdominal distention
High GRV: 200 vs 500ml
Vomiting
Diarrhea
Aspiration

41. Gastric Residuals
Incidence of complications higher in the control group
Diet volume ratio similar in both groups (diet received/diet prescribed)

42. Summary Nutrition is vitally important in ICU patients
Understand the nutritional needs of your patients
Calculate requirement and/or get a nutrition consult
Use the gut whenever possible
Nutrition should commence by day 3 and not later than day 7