College Answer

A) A number of metabolic derangements affect fuel utilization:

• Insulin resistance

• Impaired glucose tolerance,

• Increased fatty acid mobilization

• Hyperlipidemia

• Obese patients, compared to lean counterparts, may have accelerated protein degradation and depletion of lean body mass.

• “Metabolic X syndrome” may exist: insulin resistance, hyperinsulinemia, hyperglycaemia, coronary artery disease, hypertension, and hyperlipidemia.

• Obese patients are more likely to have a pre-existing pro inflammatory state.

• Obese patients have increased resting energy expenditure secondary to increased BMI, with central adipose tissue being more metabolically active than peripheral adipose tissue.

b) Assessment

• Assess patterns of weight change and nutrition intake prior to the admission

• Anthropometrics –actual body weight, ideal body weight, usual body weight, height, BMI, and waist circumference should be determined

• (Biomarkers of the metabolic syndrome; triglycerides, cholesterol, glucose serum albumin and pre-albumin)

c) Nutritional Regimen

• High protein (anabolic) hypocaloric feeding (reduced complications from overfeeding) should be provided to the obese critically ill patient regardless of whether the route of nutrition therapy is enteral or parenteral

• Most studies using this method give 11-14 kcal/kg/actual BW per day or 22-25 kcal/kg IBW per day- equates to about 60-70% of calorie requirement determined by indirect calorimetry or predictive equation.

• Protein requirements should be met to maximise protein synthesis and preserve lean body mass (> 2.0g/kg IBW/d for class 1 and 2 obesity and > 2.5g/kg IBW/d for class 3).

Discussion

The spectrum of metabolic derangements present in the obese ICU patient is detailed elsewhere.  In short, these are the major metabolic abnormalities one can expect from an obese patient in the ICU:

• Insulin resistance and impaired glucose tolerance

• Increased fatty acid mobilization and hyperlipidemia

• Accelerated protein degradation
• The proinflammatory state of obesity
• The endocrine derangements due to an excess of fatty tissue
• The increased resting metabolic rate of obesity

Assessment of nutritional status is also detailed elsewhere; in brief the assessment takes the shaped of a structured approach, from history to investigatons:

History:

• 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)

Examination:

• Observed quality of nails and hair
• Subcutaneous fat measurements (triceps)
• Muscle bulk and muscle tone of quadriceps and deltoids
• Presence of oedema and ascites

Anthropometry

• BMI
• Ideal body weight
• Lean body mass

Biochemistry:

• Cholesterol and triglycerides
• Random BSL
• HbA1C
• Serum cortisol
• TFTs
• Albumin and prealbumin

Nutrition for the obese ICU patient is presently a topic of hot debate. The most recent suggestions are summarised elsewhere. In short, the published consensus statements suggest we follow a certain pattern:

• Feed enterally wherever possible
• Hypocaloric high-protein feeding is recommended:
  • Supply 60-70% of energy requirements;
    • some authors recommend 21kcal/d of actual body weight
  • Oversupply protein:
    • 2.0-2.5g/kg of ideal body weight, or
    • 1.3-1.5g/kg of actual body weight