Energy and Protein Requirements

1. Energy and Protein Requirements Robert Kushner, MD Northwestern University Feinberg School of Medicine rkushner@northwestern.edu

2. 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 LEAN BODY MASS Nitrogen Death 70%

3. Starvation and Protein-Energy Malnutrition:Clinical 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

4. 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

5. Mediators of the Metabolic Response • Cytokines • IL-1, IL-6, TNF- • Glucagon, Epinephrine, Norepinephrine • Corticosteroids • Eicosanoids • Leukotrienes, Thromboxanes • Growth Factors • IGF-1

6. “Fuels” Energy substrates • Free fatty acids • Triglycerides • Diet • Adipose tissue • Glucose • Starches and sugars • Diet • Glycogen • Amino acids • Protein • Diet • Tissue

7. 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

8. Relationship between Energy and Protein Requirements (1.1 g pro/kg) (1.3 g pro/kg)

9. Nitrogen equilibrium attained is at near-energy equilibrium Slope = 1.4 mg of N/kcal

10. Components of Total Daily Energy Expenditure TEF RMR ET NEAT PA RMR=resting metabolic rate; TEF=thermic effect of feeding; ET=exercise thermogenesis; NEAT=non-exercise thermogenesis

11. 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 TEF RMR PA

12. 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)

13. Estimating a Stress Factor

14. Estimating a Stress Factor

16. 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

17. 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.

18. Principles of Indirect Calorimetry

20. V02

22. 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

23. Estimated Energy Requirements

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

25. Protein RequirementFeeding High Quality Protein Average Requirement

26. 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

27. Usually measured as nitrogen 1 g N = 6.25 g Protein

29. 168 g pro (2.5 g/kg) 70 g pro (1.1 g/kg)

30. N Balance is Dependent on More than Energy

31. 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

33. Estimating Nitrogen Losses

34. 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

35. Effect of Disease and Traumaon Protein Requirements (without dialysis) (with dialysis)

36. Estimated Protein Requirements

37. 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