Energy and Protein Energy and Protein RequirementsRequirements

Robert Kushner, MDNorthwestern University Feinberg School of Medicine

rkushner@northwestern.edu

Starvation and Starvation and Protein-Energy Malnutrition:Protein-Energy Malnutrition:

Importance of Lean Body MassImportance of Lean Body MassHealth 100%

Decreased muscle mass: skeletal, cardiac

Decreased visceral proteins: albumin

Impaired immune response

Impaired wound healing

Impaired organ function

Nitrogen Death 70%

LEAN BODY MASSLEAN BODY MASS

Starvation and Starvation and Protein-Energy Malnutrition:Protein-Energy Malnutrition:

Clinical ImplicationsClinical Implications

Fatigue, general weakness

Lack of initiative

Bedridden

Apathy

Complete Exhaustion

Decreasedmuscle mass

Impaired wound healing

Decreased visceral proteins

Organ failure

10 weeks5 weeks

“Normal”“Catabolic Patients”

Acceleration of Malnutrition Acceleration of Malnutrition due to Metabolic Stressdue 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

Mediators of the Mediators of the Metabolic ResponseMetabolic Response

• Cytokines– IL-1, IL-6, TNF-

• Glucagon, Epinephrine, Norepinephrine• Corticosteroids• Eicosanoids

– Leukotrienes, Thromboxanes

• Growth Factors– IGF-1

“Fuels” Energy substrates• Free fatty acids

– Triglycerides• Diet• Adipose tissue

• Glucose– Starches and sugars

• Diet• Glycogen

• Amino acids– Protein

• Diet• Tissue

Energy Reserves of a 70 kg man, Energy Reserves of a 70 kg man, expressed in kcalexpressed in kcal

Adipose tissue135,000

Protein*24,000

Liver glycogen280

Muscle glycogen480

*Body protein, which can readily beconverted to glucose, is not stored for anyreason, since all proteins are functional

Relationship between Energy and Protein Requirements

(1.3 g pro/kg)(1.1 g pro/kg)

Nitrogen equilibrium attained is at near-energy equilibrium

Slope = 1.4 mg of N/kcal

Components of Total Daily Energy Expenditure

RMRTEF

ET

NEAT

PA

RMR=resting metabolic rate; TEF=thermic effect of feeding;ET=exercise thermogenesis; NEAT=non-exercise thermogenesis

How Do we Estimate or Measure our Patient’s 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

RMRTEF

PA

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)

Estimating a Stress Factor

Estimating a Stress Factor

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 2006;81:809

Fuel + O2

CO2 +

H2OADP

ATP

Reality: multiple steps with multiple intermediates, but this net reaction.

Pot

enti

al e

nerg

y

Captured energy (40%)

Lost as heat

Principles of Indirect Calorimetry

Metabolic Coupling

Principles of Indirect Calorimetry

V02

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

Estimated Energy Estimated Energy RequirementsRequirements

Resting state 20-30 kcal/kg d

Uncomplicated postoperative

25-35 kcal/kg d

Nutritionally depleted 30-40 kcal/ kg d

Hypermetabolic (trauma, sepsis)

35-40 kcal/ kg d

Changes with age of mean energy and protein requirements

Millward, D. J. J. Nutr. 2004;134:1588S-1596S

Protein RequirementFeeding High Quality

Protein

-8

-7

-6

-5

-4

-3

-2

-1

0

1

0 0.2 0.4 0.6 0.8 1

Protein Intake, gm/ kg/ d

Nit

rogen B

ala

nce

, unit

s

AverageRequirement

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

Usually measured as nitrogen

1 g N = 6.25 g Protein

168 g pro (2.5 g/kg)

70 g pro (1.1 g/kg)

N Balance is Dependent on More than Energy

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

Estimating Nitrogen Losses

Non-urea nitrogen losses(open abdomen)

*Traditional method of estimating N balance = N intake – (24 hr UUN + 4)

Cheatham et al. Crit Care Med 2007;35:127

Effect of Disease and Traumaon Protein Requirements

0

0.5

1

1.5

2

2.5

Normal

Infe

ctio

n

Pancr

eatit

isBurn

Mul

titra

uma

Hepat

itis

Encephal

opathy

Acute

Ren

al

Chronic

Ren

al

g/k

g

(with

out d

ialysis

)

(with

dia

lysis

)

Estimated Protein Estimated Protein RequirementsRequirements

Resting state 0.8-1.0 g/kg d

Uncomplicated postoperative

1.0-1.3 g/kg d

Depleted patients 1.3-1.7 g/kg d

Hypermetabolic (trauma, sepsis)

1.5-2.0 g/kg d

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