Clinical Nutrition Overview

Question 1

Describe the six characteristics recommended for the identification of adult malnutrition.

Answer 1

• Weight loss over time (assess as a percentage of baseline)
• Insufficient energy intake (assess recent intake with estimated requirements)
• Loss of muscle mass
• Loss of fat mass
• Fluid accumulation
• Diminished strength (shown by grip strength)

Question 2

State the limitations to use of serum proteins to characterize nutritional status.

Answer 2

• Albumin and Prealbumin:
o Lack sensitivity and specificity for malnutrition
o Good indicator for risk of morbidity and mortality
o Can show underlying injury, disease, or inflammation
o Values impacted by liver or renal disease
• C-reactive Protein:
o Elevated with active inflammatory process
• BUN/Cr:
o May be affected by reduced body mass
• CBC:
o Screen for nutritional anemias

Question 3

Identify components of total energy expenditure

Answer 3

Basal metabolic rate (BMR)
o Minimum energy to maintain life processes; the internal work
o Measure: Fast overnight 12-15 hrs, subject is supine, awake, motionless, in a thermo-neutral environment
o Affected by age, gender, body composition, nutritional and health status
o 60-75% of total energy expenditure
o Sleeping metabolic rate about 5-10% lower than BMR
Resting Energy Expenditure (REE)
o Measure: Fast 3-4 hours, time of day nor prior activity not controlled, thermo-neutral environment
o About 10-20% higher than BMR
o Fat-free mass is best predictor of REE
• REE decreases with obesity since less contributions of metabolically active tissues
Thermogenesis
o Increases BMR in response to stimuli unassociated with muscular activity
o Thermal Effect of Food (TEF): increase in energy expenditure from food consumption
• Digestion, absorption, processing or storing nutrients
• Varies depending of type of food: 5-10% above BMR for CHO, 0-5% for fat, 20-30% for protein
o Cold and heat exposure
• Induces thermogenesis
• May change energy expenditure by 2-5% (usually not a factor due to clothing)
Physical activity
o Most variable part of TEE
o Not a factor in most hospitalized patients, may be increased with brain-injured or neurological patients due to activity
Growth, Pregnancy, and Lactation
o Growth: need energy for tissue deposition
o Pregnancy: increases for mother, baby, weight-bearing work
o Lactation: energy costs due to milk synthesis

Question 4

Describe principles of determining energy needs by direct calorimetry

Answer 4

o Measures heat emitted from body over given period
o Measure changes in temperature of air or water of enclosed chamber holding subject
o Research purposes only

Question 5

Describe principles of determining energy needs by indirect calorimetry

Answer 5

o Measures REE by measuring O2 consumption and CO2 production
o Modified Weir Formula (ignores protein metabolism)
• EE = (3.94 x VO2) + (1.11 x VCO2)
o IC measurements of REE correlates with true REE
o Need to meet assumptions: pH, temperatures, exogenous CO2 sources, sources of O2 intake/loss
o Often can’t use in ICU

Question 6

Describe principles of determining energy needs by doubly-labeled water methodologies

Answer 6

o Estimates TEE with two isotopic forms of water
• 2H2O labels water pool
• H218O labels water and bicarbonate pools
o Monitor disappearance rate of isotopes for 7-21 days
o Difference between 2H2O and H218O used to calculate VCO2
o Used to validate IC
o Uses in research (requires expensive isotopes and equipment)

Question 7

Describe methods for estimating energy intake for healthy and hospitalized individuals.

Answer 7

Mifflin St. Jeor equation
o Male: (10 x wt kg) + (6.25 x ht cm) – (5 x age) + 5
o Female: (10 x wt kg) + (6.25 x ht cm) – (5 x age) -161
o Activity adjustments

Calculate based on kcal/kg
o Hospitalized patients: 25-35 kcals/kg
o Obese patients: hypocaloric, high protein diet based on ideal body weight
• 22-25 kcal/kg IBW or
• 25-30 kcal/kg IBW and 2-2.5 g protein/kg IBW

Question 8

List the essential and non-essential amino acids

Answer 8

Essential amino acids:
o	Remember: PVT TIM HALL
o	Phenylalanine
o	Valine
o	Tryptophan
o	Threonine
o	Isoleucine
o	Methionine
o	Histidine
o	Arginine* (conditionally) 
o	Leucine
o	Lysine
Non-essential
o	 Alanine, aspartic acid, asparagine, glutamic acid, glutamate, glycine, proline, serine 

Complementing proteins: lysine is limiting in cereal grains, methionine is limiting in legumes
o Complement within a day to complete aa pool

Question 9

Describe recommended protein intakes for healthy and hospitalized individuals

Answer 9

Healthy:
o 0.8 g/kg/day for adults
o 1.1 g/kg/day for pregnant and lactating women
o 1.5 g/kg/day for infants
Hospitalized
o 1.5 – 2.0 g/kg or 20-25% calories
o Greater needs due to rapid breakdown, GNG, support immune system, promote healing

Question 10

Summarize the limitations of nitrogen balance to assess protein needs in hospitalized patients

Answer 10

Method to measure protein turnover
N balance = N intake – N output
o N output (g/d) = urinary urea N + 20% of urinary urea losses + 2g (stool and skin)
o Urinary urea N normally is 80% of total urine nitrogen
o Assumes a standard value for non-urinary losses
Invalidating reasons:
o Renal dysfunction
o Edema
o Diarrhea/ostomy/fistula losses
o Significant respiratory secretions
o Chest tube output
Disregards considering aa entry from protein breakdown or uptake for protein synthesis
Could get positive N balance:
o Increasing protein synthesis
o Increasing synthesis more than breakdown
o Decreasing breakdown
o Decreasing breakdown more than synthesis