Energy and Protein Requirements

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Energy and Protein Requirements
Robert Kushner, MD Northwestern University
Feinberg School of Medicine rkushner_at_northwestern.
edu
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Starvation and Protein-Energy MalnutritionImpor
tance of Lean Body Mass
Health 100
Decreased muscle mass skeletal, cardiac
Decreased visceral proteins albumin
Impaired immune response
Impaired wound healing
Impaired organ function
LEAN BODY MASS
Nitrogen Death 70
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Starvation and Protein-Energy MalnutritionClini
cal Implications
Fatigue, general weakness
Decreased muscle mass
Lack of initiative
Bedridden
Decreased visceral proteins
Apathy
Impaired wound healing
Complete Exhaustion
Organ failure
Normal
Catabolic Patients
10 weeks
5 weeks
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Acceleration of Malnutrition due to Metabolic
Stress

• Energy expenditure is increased
• tachycardia, fever, increased RMR
• Catabolism of muscle occurs due to increased
  protein needs
• stress hormones stimulated
• cytokines released
• weakness, loss of muscle tissue, increased
  urinary urea nitrogen

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Mediators of the Metabolic Response

• Cytokines
• IL-1, IL-6, TNF-?
• Glucagon, Epinephrine, Norepinephrine
• Corticosteroids
• Eicosanoids
• Leukotrienes, Thromboxanes
• Growth Factors
• IGF-1

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Fuels Energy substrates

• Free fatty acids
• Triglycerides
• Diet
• Adipose tissue
• Glucose
• Starches and sugars
• Diet
• Glycogen
• Amino acids
• Protein
• Diet
• Tissue

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Energy Reserves of a 70 kg man, expressed in kcal
Adipose tissue 135,000
Protein 24,000
Liver glycogen 280 Muscle glycogen 480
Body protein, which can readily be converted to
glucose, is not stored for any reason, since all
proteins are functional
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Relationship between Energy and Protein
Requirements
(1.1 g pro/kg)
(1.3 g pro/kg)
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Nitrogen equilibrium attained is at near-energy
equilibrium
Slope 1.4 mg of N/kcal
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Components of Total Daily Energy Expenditure
TEF
RMR
ET
NEAT
PA
RMRresting metabolic rate TEFthermic effect of
feeding ETexercise thermogenesis
NEATnon-exercise thermogenesis
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How Do we Estimate or Measure our Patients
Energy Requirements?

• Total energy expenditure RMR TEF PA
• 3 common methods used
• Estimate RMR, then use a stress and PA multiplier
• Measure RMR, then use a PA multiplier
• Use a simple estimate for all patients

TEF
RMR
PA
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Estimating RMR

• Harris Benedict, 1919
• Men RMR 66.5 (13.8 x weight) (5 x height)
  (6.8 x age)
• Women RMR 655.1 (9.6 x weight) (1.8 x
  height) (4.7 x age)
• Mifflin-St. Jeor, 1990
• Men RMR (10 x weight) (6.26 x height) (5
  x age) 5
• Women RMR (10 x weight) (6.26 x height)
  (5 x age) 161
• Institutes of Medicine (IOM)
• World Health Organization (WHO)

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Estimating a Stress Factor
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Estimating a Stress Factor
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Energy Expenditure in Hospitalized Patients

• 1256 patients in 19 studies
• Postoperative (28)
• Trauma or sepsis (26)
• Cancer (18)
• Pulmonary disease (9)
• Excluded individuals with fever (11/C), burns
  (140 to 150), and head injuries (120 to 145)
• Mean stress (SD) factor was 113 (10.9) above
  predicted by Harris Benedict equation

Miles JM. Mayo Clin Proc 200681809
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Principles of Indirect CalorimetryMetabolic
Coupling
Fuel O2
Lost as heat
ATP
Potential energy
Captured energy (40)
CO2 H2O
ADP
Reality multiple steps with multiple
intermediates, but this net reaction.
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Principles of Indirect Calorimetry
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V02
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Assumptions of Indirect Calorimetry

• The gaseous input and exhaust products from the
  metabolic combustion process (O2 and CO2) pass
  only through the nose and mouth
• Chest tubes, air leaks
• O2 input is fixed and constant
• Nasal cannula, ventilator changes
• All nutrients are metabolized to the end products
  of CO2, H2O and urea
• Renal failure, diabetic ketoacidosis
• Other causes of altered respiration, e.g.,
  metabolic alkalosis and acidosis, hyper- and
  hypoventilation, oxygen debt, are not present
• Protein is assumed to contribute 12.5 of caloric
  expenditure (Weir equation)
• Excessive protein breakdown, high protein diet

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Estimated Energy Requirements
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Changes with age of mean energy and protein
requirements
Millward, D. J. J. Nutr. 20041341588S-1596S
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Protein RequirementFeeding High Quality Protein
Average Requirement
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Protein Requirements

• Estimated Average Requirement (EAR) 105 mg
  N/kg/d or 0.66 g/kg/d
• Recommended Dietary Allowance (RDA)
• x 2 SD (97.5 of population)
• 0.66 x (1 2 x 0.125) 0.80 g/kg/d
• 70 kg male 56 g/d
• 55 kg female 46 g/d

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Usually measured as nitrogen 1 g N 6.25 g
Protein
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168 g pro (2.5 g/kg)
70 g pro (1.1 g/kg)
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N Balance is Dependent on More than Energy
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Measuring Protein (Nitrogen) Balance

• N balance evaluates adequacy of protein intake
  relative to need
• N metabolism is dependent on both energy and
  protein intake adequate minerals
• N balance (g/d) (protein intake/6.25)
  (urinary nitrogen mostly urea fecal losses
  obligatory losses)
• Clinically, measure total urinary urea N (UUN)
  2-4 g for non-urea losses

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Estimating Nitrogen Losses
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Non-urea nitrogen losses(open abdomen)
Traditional method of estimating N balance N
intake (24 hr UUN 4)
Cheatham et al. Crit Care Med 200735127
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Effect of Disease and Traumaon Protein
Requirements
(without dialysis)
(with dialysis)
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Estimated Protein Requirements
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Conclusion

• Adequate energy and protein must be provided to
  prevent auto-cannibalism, progressive
  malnutrition and poor clinical outcomes
• Energy and protein balance are inter-related
• Requirements should be estimated and/or measured
  for each patient