Presentation is loading. Please wait.

Presentation is loading. Please wait.

Dr. Elizabeth Weekes Department of Nutrition & Dietetics Guys & St. Thomas Hospitals NHS Foundation Trust London Controversies in the determination of.

Similar presentations


Presentation on theme: "Dr. Elizabeth Weekes Department of Nutrition & Dietetics Guys & St. Thomas Hospitals NHS Foundation Trust London Controversies in the determination of."— Presentation transcript:

1 Dr. Elizabeth Weekes Department of Nutrition & Dietetics Guys & St. Thomas Hospitals NHS Foundation Trust London Controversies in the determination of energy requirements

2

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 BMR DIT Activity

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 – 29 o C) 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 BMR DIT Activity Indirect calorimetry Doubly-labelled water

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 BMR + Stress DIT Activity 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/m 2 REE < 105 % HB in 14 patients REE > 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/m 2 REE 123 (+ 11) % HB on admission REE 113 (+ 14) % HB on discharge (REE > 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

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

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


Download ppt "Dr. Elizabeth Weekes Department of Nutrition & Dietetics Guys & St. Thomas Hospitals NHS Foundation Trust London Controversies in the determination of."

Similar presentations


Ads by Google