Chronic malnutrition and nutritional assessment

Definitions:

• Marasmus - balanced diet but inadequate energy - manifests as cachexia. Also called protein-energy malnutrition.
• Kwashiorkor - inadequate as well as unbalanced diet, with more calories than protein. Results in fluid retention, sarcopaenia, loss of fat stores; may have low albumin. Often seen accompanying sepsis or after trauma.
• Sarcopaenia - age-related progressive loss of muscle mass and strength
  • increased morbidity after abdominal elective surgery

Evidence for impact of chronic malnutrition

• ESPEN says that 'metabolic risk' is a significant factor for hospital mortality, especially in elderly
• Can predict length of stay and complications for various operations
• Weight loss and serum albumin concentration were predictive parameters for post-operative outcome in one meta-analysis

Overall approach to identifying and diagnosing malnutrition

• Use MUST to screen for at-risk patients
• Then use GLIM criteria to confirm diagnosis, and establish severity

Components of malnutrition assessment:

Biochemical

• • No single reliable measure
  • Albumin is somewhat useful in a patient at their baseline, but not acutely - it reflects the level of catabolism, not the underlying nutritional insufficiency
  • Hypoalbuminaemia is almost inevitable in an unwell patient because of variations in fluid composition and capillary hyper-permeability, and does not necessarily reflect nutritional status
    • Half-life 20 days
    • Half-life of pre-albumin is 48 hours

Body weight and anthropometry

• • Clinical findings
    • Cachexia, angular cheilitis, hair thinning
  • Simple method - estimate weight loss from pre-morbid weight
  • Unintentional weight loss of 10% in six months is a good measure of poor prognosis
  • BMI - weight/height squared
    • <18.5 = nutritional impairment
    • <15 significant hospital mortality association
    • Can be unreliable in unwell patients
  • Anthropometric techniques are indirect measures of body fat and muscle mass. Insufficiently accurate to guide management in individual patients. Only useful as trends in the same patient over time.
    • Skinfold thickness
    • Mid-arm circumference
    • Bioelectric impedance permits estimation of intra-and extra-cellular fluid volumes

Clinical

• • 'Subjective global assessment'
    • Risk of malabsorption
    • Adequacy of dietary intake
    • Selected nutritional blood tests
    • 'MUST' tool

Screening:

• Assessment of nutritional status is less important than identification of patients at risk of poor nutritional status
  • Single most important factor is unintentional weight loss >5% over one month or >10% over 6 months
  • 'Disease-related malnutrition' is probably more subtle than suggested by the weight-related definition from WHO - it is plausible for obese patients to have malnutrition
  • Chronic low-grade inflammation may be a component of malnutrition
• MUST (Malnutrition Universal Screening Tool) - see above

Diagnosing:

• BMI + weight loss + muscle assessment + dietary intake +/- intake
• ESPEN diagnostic criteria (2012)
  • BMI <18.5 OR
  • Weight loss (>10% over six months OR >5% over three months) AND (low BMI OR low fat-free mass index)
• PG-SGA tool uses a combination of subjective assessments from the patient, and clinician assessments, to grade chronic malnutrition and suggest interventions
• GLIM criteria (2018) incorporates phenotypic criteria, aetiology and severity
  • Diagnosis - one phenotypic and one aetiologic criteria
    • Phenotype - unintentional weight loss (>5% in six months, >10% in longer time), low BMI(<20 for <70yo, <22 for >70yo), or reduced muscle mass
    • Aetiology - reduced food intake or absorption, or underlying inflammation due to acute disease/injury or chronic disease
  • Severity
    • Stage 1 or stage 2 for each criteria