Energy and Protein Requirements Robert Kushner, MD Northwestern University Feinberg School of Medicine

Starvation and Protein-Energy Malnutrition: Importance of Lean Body Mass Health 100% Decreased muscle mass: skeletal, cardiac Decreased visceral proteins: albumin Impaired immune response Impaired wound healing Impaired organ function Nitrogen Death 70% LEAN BODY MASS

Starvation and Protein-Energy Malnutrition: Clinical Implications Fatigue, general weakness Lack of initiative Bedridden Apathy Complete Exhaustion Decreased muscle mass Impaired wound healing Decreased visceral proteins Organ failure 10 weeks 5 weeks “Normal” “Catabolic Patients”

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

Mediators of the Metabolic 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, 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

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 RMR TEF 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 RMR TEF PA

Estimating RMR Harris Benedict, 1919 –Men: RMR = (13.8 x weight) + (5 x height) – (6.8 x age) –Women: RMR = (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

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 + O 2 CO 2 + H 2 O ADP ATP Reality: multiple steps with multiple intermediates, but this net reaction. Potential energy Captured energy (40%) Lost as heat Principles of Indirect Calorimetry Metabolic Coupling

Principles of Indirect Calorimetry

V0 2

Assumptions of Indirect Calorimetry The gaseous input and exhaust products from the metabolic combustion process (O 2 and CO 2 ) pass only through the nose and mouth –Chest tubes, air leaks O 2 input is fixed and constant –Nasal cannula, ventilator changes All nutrients are metabolized to the end products of CO 2, H 2 O 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 Requirements

Changes with age of mean energy and protein requirements Millward, D. J. J. Nutr. 2004;134:1588S-1596S

Protein Requirement Feeding High Quality Protein Average Requirement

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) 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 Trauma on Protein Requirements (without dialysis) (with dialysis)

Estimated Protein Requirements

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