Dr. Elizabeth WeekesDepartment of Nutrition & DieteticsGuy’s & St. Thomas’ Hospitals NHS Foundation TrustLondon

Controversies in the determination of energy Controversies in the determination of energy requirementsrequirements

ControversiesControversies

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 don’t?

Total Energy ExpenditureTotal Energy Expenditure

BMR

DIT

Activity

Methods of estimating energy Methods of estimating energy expenditureexpenditure

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

Prediction equationsPrediction 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)

Basal metabolic rateBasal 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

Conditions essential for measuring Conditions essential for measuring BMRBMR

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)

Measured Energy Expenditure (MEE)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

MEE in healthy subjectsMEE in healthy subjects

BMR

DIT

Activity

Indirectcalorimetry

Doubly-labelledwater

MEE in clinical studiesMEE 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

MEE in diseaseMEE in disease

BMR +Stress

DIT

Activity

Indirectcalorimetry

ControversiesControversies

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 don’t?

Reviewing the literatureReviewing 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

Energy requirements in COPDEnergy requirements in COPD

Schols et al. (1996)Age 61 (+ 6) years; BMI 23.5 (+ 4.2) kg/m2

REE < 105 % HB in 14 patientsREE > 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 admissionREE 113 (+ 14) % HB on discharge(REE > 110 % HB in 10 patients at discharge) 23 acute COPD patients admitted to hospital

ControversiesControversies

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 don’t?

Estimating requirements in clinical Estimating requirements in clinical practicepractice (I) (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

Metabolic response to injuryMetabolic response to injury

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Time (hours)

Injury

Necrobiosis and death

24 48 96 120

Assessing metabolic stressAssessing 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

Stress factorsStress 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

Estimating requirements in clinical Estimating requirements in clinical practicepractice (I) (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

Physical activityPhysical activity

Assumes normal neuro-muscular functionReview literature for patients with abnormal function

e.g. brain injury, Parkinson’s disease, cerebral palsy, motor neurone disease and Huntington’s chorea

Prolonged and active physiotherapy

Increased effort of moving injured/painful limbs

Mechanical inefficiency e.g. COPD (Baarends et al., 1997)

Physical activityPhysical 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

Estimating requirements in clinical Estimating requirements in clinical practicepractice (I) (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)

Estimating requirements in clinical Estimating requirements in clinical practice IIpractice 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

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

I don’t?I don’t?

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?

ConclusionsConclusions

Estimated requirements are only a starting point• Set realistic goals of treatment for each patient• Monitor and amend as patient’s 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