Estimating nutritional requirements – what is the evidence?

1
Controversies in the determination of energy
requirements
Dr. Elizabeth Weekes Department of Nutrition
Dietetics Guys St. Thomas Hospitals NHS
Foundation Trust London
2
(No Transcript)
3
Controversies

• Is measured energy expenditure (MEE) always the
  most accurate way to determine energy
  requirements?
• Is it valid to extrapolate results from a study
  population to an individual patient?
• What should we do in clinical practice?
• If I feed my patient to estimated energy
  requirements will he/she do better than if I
  dont?

4
Total Energy Expenditure
DIT
Activity
BMR
5
Methods of estimating energy expenditure

• Indirect calorimetry
• Short-term measurements (up to 24 hours)
• Hood/ventilator modes
• Doubly-labelled water technique
• Long-term measurements (several weeks)
• Cost and technical considerations
• Measures Total Energy Expenditure
• Prediction equations fudge factors

6
Prediction equations

• May over or under-estimate compared with measured
  energy expenditure (MEE)
• Inadequately validated
• Poor predictive value for individuals
• Open to misinterpretation
• (Cortes Nelson, 1989 Malone, 2002 Reeves
  Capra, 2003)

7
Basal metabolic rate

• Minimal intra-individual variation 3
• Inter-individual variation 10 depending on-
• proportions of body cell mass and metabolically
  active organs and tissues
• thyroid function
• circadian rythms

8
Conditions essential for measuring BMR

• Post-absorptive (12 hour fast)
• Lying still at physical and mental rest
• Thermo-neutral environment (27 29oC)
• No tea/coffee/nicotine in previous 12 hours
• No heavy physical activity previous day
• Gases must be calibrated
• Establish steady-state ( 30 minutes)
• If any of the above conditions are not met
• Resting Energy Expenditure (REE)

9
Measured Energy Expenditure (MEE)

• Measured in clinical setting by indirect
  calorimetry
• (rarely available in UK hospitals)
• Recommended in certain conditions e.g. liver
  disease, obesity, critical illness (ASPEN, 2002)
• Needs to be measured correctly in order to
  provide valid and reliable data

10
MEE in healthy subjects
Activity
DIT
Doubly-labelled water
BMR
Indirect calorimetry
11
MEE in clinical studies

• Calibration
• How long and how often to measure
• Achieving a steady-state
• Lying in bed, awake and aware
• No social or physical interactions
• Avoid haemodialysis and filtration
• Patient/apparatus interface
• Hood/canopy
• Ventilated patients

12
MEE in disease
Activity
DIT
BMR Stress
Indirect calorimetry
13
Controversies

• Is measured energy expenditure (MEE) always the
  most accurate way to determine energy
  requirements?
• Is it valid to extrapolate results from a study
  population to an individual patient?
• What should we do in clinical practice?
• If I feed my patient to estimated energy
  requirements will he/she do better than if I
  dont?

14
Reviewing the literature

• Patient demography
• Sample size
• Diagnosis
• Severity of illness/injury and metabolic status
• Nutritional status
• Nutritional intake
• Temperature (room and patient)
• Therapeutic interventions e.g. ventilation, drugs
• Methodology

15
Energy requirements in COPD

• Schols et al. (1996)
• Age 61 ( 6) years BMI 23.5 ( 4.2) kg/m2
• REE lt 105 HB in 14 patients
• REE gt 120 HB in 16 patients (weight-losing, ?
  FFM, ? CRP and ? acute phase proteins)
• 30 stable COPD patients admitted to
  rehabilitation unit
• Vermeeren et al., (1997)
• Age 63 ( 8) years BMI 23.0 ( 3.2) kg/m2
• REE 123 ( 11) HB on admission
• REE 113 ( 14) HB on discharge
• (REE gt 110 HB in 10 patients at discharge)
• 23 acute COPD patients admitted to hospital

16
Controversies

• Is measured energy expenditure (MEE) always the
  most accurate way to determine energy
  requirements?
• Is it valid to extrapolate results from a study
  population to an individual patient?
• What should we do in clinical practice?
• If I feed my patient to estimated energy
  requirements will he/she do better than if I
  dont?

17
Estimating requirements in clinical practice (I)

• Assess metabolic state
• Is my patient metabolically stressed, recovering
  or anabolic
• Is there a risk of re-feeding syndrome?
• Establish physical activity level
• Is the patient sedated, bed-bound, mobile on
  ward, receiving physiotherapy, at home
• Determine goals of treatment
• e.g. minimise losses, weight maintenance or
  weight change

18
(No Transcript)
19
Metabolic response to injury
20
Assessing metabolic stress

• Stressed
• ? temperature
• ? urea
• ? white cell count
• ? C-reactive protein
• ? albumin
• ? insulin resistance
• Oedema
• N.B. Stress response may be blunted in
  immuno- compromised and elderly patients

21
Stress factors

• Timing of measurements
• Over (hyperalimentation) vs. under-feeding
• Changes in therapeutic interventions
• e.g. improved wound care, anti-pyretics,
  sedation, control of ambient room temperature
• ? Err towards lower end of the range and monitor

22
Estimating requirements in clinical practice (I)

• Assess metabolic state
• Is my patient metabolically stressed, recovering
  or anabolic
• Is there a risk of re-feeding syndrome?
• Establish physical activity level
• Is the patient sedated, bed-bound, mobile on
  ward, receiving physiotherapy, at home
• Determine goals of treatment
• e.g. minimise losses, weight maintenance or
  weight change

23
Physical activity

• Assumes normal neuro-muscular function
• ?Review literature for patients with abnormal
  function
• e.g. brain injury, Parkinsons disease, cerebral
  palsy, motor neurone disease and Huntingtons
  chorea
• Prolonged and active physiotherapy
• Increased effort of moving injured/painful limbs
• Mechanical inefficiency e.g. COPD (Baarends et
  al., 1997)

24
(No Transcript)
25
Physical activity

• Free living individuals have higher energy
  expenditure due to physical activity
• Nursing home and house-bound patients may have
  similar activity levels to hospitalised patients
• For active patients in the community a PAL should
  be added

26
Estimating requirements in clinical practice (I)

• Assess metabolic state
• Is my patient metabolically stressed, recovering
  or anabolic
• Is there a risk of re-feeding syndrome?
• Establish physical activity level
• Is the patient sedated, bed-bound, mobile on
  ward, receiving physiotherapy, at home
• Determine goals of treatment
• Should I aim to minimise losses, maintain weight
  or achieve weight change (loss or gain)

27
Estimating requirements in clinical practice II

• Be aware of the literature on energy requirements
  in your patient group (and any gaps in the
  evidence)
• Compare your patient with available literature
  and either assign relevant stress factor OR
  adjust for weight change
• Monitor, review and amend requirements as
  clinical condition, physical activity and
  nutritional goals change

28
If I feed my patient to estimated energy
requirements will he/she do better than if I
dont?

• Over-feeding is not good
• (Askanazi et al., 1980 Lowry Brenman, 1979
  Kirkpatrick et al., 1981)
• Is under-feeding always bad?
• Should we start everyone on 1500 kcal/day?

29
Conclusions

• Estimated requirements are only a starting point
• Set realistic goals of treatment for each patient
• Monitor and amend as patients condition changes
• Review and critically appraise the literature
• Be aware of gaps in the evidence
• Understand the limitations of guidelines
• Check applicability to your patients
• Contribute to research and audit projects