Outline your approach to the assessment of nutritional status in a critically ill patient, including the use of appropriate laboratory tests.
History and physical examination:
Indicators of malnutrition – recent involuntary weight loss, changes in appetite or bowel habit, presence of persistent GI symptoms, muscle wasting, signs of specific micro-nutrient deficiency e.g. glossitis, angular stomatitis, anaemia, bleeding gums, skin/hair/nail condition.
Ancillary blood tests: serum hepatic protein levels are linked to nutritional status and severity of illness.
• Serum albumin and pre-albumin levels. ( Albumin will be a better indicator of chronic nutritional status and pre-albumin serves more as a marker of changes in current nutritional status).
• Transferrin and coagulation factors: Useful but may more reflect the poor synthetic function of the liver in this case than nutritional deficiency per se.
• Fat-soluble vitamin deficiency levels of vitamins A, D and E should be checked.
Water-soluble vitamin deficiency, (thiamine), is common in alcoholic liver disease and therefore levels of thiamine and other treatable vitamins e.g. zinc, selenium, Vit B12 and folate should also be checked.
(1) delayed hypersensitivity skin testing
(2) total lymphocyte count
(3) anthropometric measurements e.g. mid-arm muscle circumference and skin-fold thickness
(4) indirect calorimetry to measure energy expenditure – metabolic cart, VO2, VCO2,
(6) nitrogen balance – but calculations inaccurate in liver and renal failure.
An extensive examination of the methods of nutritional assessment is available elsewhere:
- Assessment of nutritional status
- Predictive equations to estimate nutritional requirements
- Estimation of energy expenditure by indirect calorimetry
- Estimation of energy expenditure by the reverse Fick method
- Daily nutritional requirements of the critically ill patient
In brief, these are the key features one should mention in such an answer:
- Premorbid weight and the pattern of its change
- Premorbid nutritional routine
- Diseases affecting gastrointestinal function (eg. coeliac disease)
- Disease affecting satiety control (eg. Prader-Willi syndrome)
- Factors influencing metabolic substrate utilisation (eg. thyroid dysfunction, hypoadrenalism, Cushings disease or corticosteroid therapy)
- Observed quality of nails and hair (an indicator of chronic protein intake)
- Subcutaneous fat measurements (triceps)
- Muscle bulk and muscle tone of quadriceps and deltoids
- Presence of oedema and ascites
- Evidence of any specific micronutrient deficiency
- Ideal body weight
- Lean body mass
Biochemistry and physiology:
- Cholesterol and triglycerides
- Random BSL
- Serum cortisol
- FBC for lymphocyte count
- Delayed hypersensitivity skin-testing
- Albumin and prealbumin
- Calculation of nitrogen balance
- Micronutrient levels:
- Fat-soluble vitamins A, D and E
- Vitamin B12
- Indirect calorimetry
http://www.criticalcarenutrition.com/ is an excellent resource for all things nutrition-related.
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