Session: How to evaluate body composition in fluid-resuscitated patients

Bioimpedance can make it

Julius Grunow  (Berlin, Germany)

 

BMI does not reflect body composition

Obesity paradox: Decreased mortality in overweight and obese patients contrary to decreased survival in general population (excluding the underweight and morbidly obese) – ? related to greater nutritional reserve

Low skeletal muscle mass is a risk factor for mortality in mechanically ventilated pts – as measured on CT (practical limitations for ICU pts)

Bioimpedance analysis (BIA) – bedside tool, radiation-free, reflects physician estimated hydrations levels quite well in prospective clinician-blinded study

Muscle mass at L3 level on a CT is highly reflective of whole body muscle mass. Assessing muscle mass from equations using BIA values vs. CT – Talluri and Janssen equations overestimate / Kyle equation underestimates

BIA cannot accurately / directly calculate muscle mass, however the values CORRELATE well – the consistency in this ‘relative inaccuracy’ may be useful

Phase angle (PhA) correlates well with muscle density = a good marker for muscle quality

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Bioimpedance should certainly not be used

Sandra Stapel (Amsterdam, The Netherlands)

 

Body composition analysis can identify pts with nutrition risk, limited physiological reserve and predict adverse outcome (in low muscle mass)

Estimation of different body compartments using Population-specific predictive equations (combination of electrical and anthropomorphic data)

  1. Not valid in critical illness
  2. Accuracy depends on two prerequisites
  • accurate body weight (rarely available in ICU pts – often guess/estimate)
  • normal fluid distribution (almost always abnormal in inflammation and after fluid resuscitation)

Within 1st week ICU admission, phase angle (PhA) and reactance (Xc) both decrease as hydration increases

Potential applicability of BIA in ICU if

1) use weight / height-independent parameters e.g. PhA

2) measuring early in admission  (PhA on Day 1 predictive of 28-d mortality in critical illness and several other pt groups; PhA on Day 5 no longer predictive, likely due to fluid resuscitation)

Low PhA associated with 90-d mortality

Further research should focus on methods to correct BIA equations for fluid imbalance and effects of nutrition / exercise on PhA.

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Phase angle to predict ICU outcome

Mette Berger (Lausanne, Switzerland)

 

Lean body mass determines outcome; fat – energy reserves, muscle – defence

Increased pectoralis muscle area on CT – significant increase in 6-mth survival, decreased hospital mortality, more ICU-free days

Measuring LBM:

  • DEXA – not practical
  • CT – at L3 (well-validated) – not practical, radiation
  • MRI – not feasible in ICU
  • US thigh – operator variability, training required
  • BIA – precise values, portable, quick and easy to perform

Main determinants of PhA

  • In health: age, gender, BMI
  • In disease states: malnutrition (Pre-albumin, subjective global assessment), inflammation (CRP, IL-6), fluid accumulation

Lower PhA in pts with advanced cancer undergoing palliative follow-up –> worse overall survival 

Lower PhA on admission in pts who later died during ICU stay (PhA in combination with APACHE II / SAPS II scores provide multi-variable composite score for 28-d mortality)

PhA improves in pts receiving beta-hydroxy-beta-methylbutyrate (metabolite of leucine) vs placebo

 


Critical illness: Increased muscle catabolism and lung production of glutamine

  • whole body production of essential and branched-chain amino acids almost doubles
  • ICU pts low / high SOFA scores – increased glutamine production but decreased plasma [glutamine]

Pts with higher SOFA scores have significantly lower PhA

Currently ICU severity scores not specific for metabolic state

  • PhA provides additional info reflecting cell viability and possibly protein metabolism (as seen in glutamine study)
  • Pick pts who will benefit from nutritional support

 

*Phase Angle = Superior prognostic marker + most precise screening tool for impaired nutritional and functional status currently available*