November 18, 2017
Assessment of Nutrition Minimize

Assessment of Nutrition

Clinical malnutrition results from a number of factors including an inability to eat, poor diet, malabsorption and loss of nutrients. The imbalance between intake and expenditure results in a negative nitrogen balance and muscle wasting and widespread cellular dysfunction causing complications such as infection, poor wound healing, changes in drug metabolism, prolonged hospitalisation and increased mortality.

Nutritional deficiency is particularly likely to occur in patients unable to eat, after surgery or cancer treatments and in those with gastrointestinal disorders.  The overall incidence of malnutrition in hospitalised patients is approximately 50%.

Assessment of basal metabolic rate (BMR) in healthy subjects

BMR in healthy subjects  W= weight (kg)

 

age (years)

BMR (kcal/day)

mean

10-18

17.5*W +651

 

18-30

15.3*W +679

 

30-60

11.6*W +879

 

>60

13.5*W +487

 

 

 

women

10-18

12.2*W +746

 

18-30

14.7*W +496

 

30-60

8.7*W +829

 

>60

10.5*W +596

 

 

activity level

24h energy expenditure

men

inactive

BMR*1.30

 

light

BMR*1.55

 

moderate

BMR*1.78

 

heavy

BMR*2.10

 

 

 

women

inactive

BMR*1.30

 

light

BMR*1.56

 

moderate

BMR*1.64

 

heavy

BMR*1.82

 

These estimates of BMR and energy expenditure are based on healthy ambulant subjects. Hospitalised patients will have considerably greater energy requirements due to the effects of fever and inflammatory processes. These patients will need an adequate energy supply to minimise catabolic loss of muscle.

Assessment of nutritional state

Advanced malnutrition is easy to recognise but it is difficult to define early malnutrition with an aim of evaluating the requirement for nutritional support. The most practical method is to use a bedside technique based on history taking and clinical examination which uses subjective criteria - the subjective global assessment.

  1. Weight change: overall loss over past 6 months in kg, and % age loss over past 2 weeks
  2. Dietary intake change (duration in weeks): gradation from no change to starvation
  3. Gastrointestinal symptoms that have persisted for > 2 weeks: none, anorexia, nausea and vomiting
  4. Functional capacity: optimal, duration and dysfunction, type (working, ambulatory, bedridden)
  5. Disease & its relation to nutritional requirements: primary diagnosis, metabolic demand
  6. Examination: loss of subcutaneous fat, muscle wasting, dependent oedema, ascites

The subjective use of the criteria above can be used to form a nutritional assessment of an individual as:- well nourished, mildly or severely malnourished. Despite the lack of a rigid scoring system, the SGA has been shown to be reproducible, to correlate with multiple measures of body composition and, moreover, to be predictive of adverse clinical events

It should not be forgotten that obese patients, too, are malnourished and can be deficient of micronutrients. Moreover, significant loss of metabolically active lean body mass i.e. muscle, may occur and be disguised by excess adipose tissue.

It should be noted that objective measures of nutritional status may give false impressions due to the effect of disease on the measurements, the delayed clinical response to nutritional depletion and because there are wide confidence limits for nutritional measurements.

References

  • Baker JP, Detsky AS, Wesson DE, Wolman SL, Stewart S, Whitewell, Langer B, Jeejeebhoy KN. Nutritional assessment: a comparison of clinical judgement and objective measurements. NEJM 1982;306:969-72.
  • Department of Health. Dietary reference values for Food, Energy and Nutrients for the United Kingdom. HMSO, London. 1991.
  

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