Nutrition of the Critically Ill Obese Patient

OVERVIEW

High protein hypocaloric feeding is preferred for critically ill obese patients (supported by SCCM/ ASPEN joint Consensus statement)

ENERGY REQUIREMENTS

Determination

• prediction equations for REE in the obese are highly unreliable
• no consensus as to which prediction equation for REE is most accurate in obese patients
• Indirect calorimetry is the preferred method for measuring REE but this is often unavailable or impractical
• For calculation of REE the Penn State equation and adjusted HBE have the strongest evidence to support their use

BODY COMPOSITION AND METABOLIC RATE

• obese patients have increased resting energy expenditure secondary to increased BMI
• central adipose tissue is more metabolically active than peripheral adipose tissue
• adipose tissue is less metabolically active than fat free mass (FFM)
• obese patients have increased amount of lean body mass

METABOLIC DERANGEMENT IN OBESE PATIENTS

Causes — the usual response to critical illness modified by:

• Insulin resistance
• obesity is a pro-inflammatory state
• altered body composition

Effects

• Impaired glucose tolerance
  — exacerbates stress-induced hyperglycemia
• Increased fatty acid mobilization
  — high FFA plasma levels and hyperlipidemia
• accelerated protein degradation
  — depletion of lean body mass
  — high amino acid plasma levels
  — energy stores from lean mass is used preferentially in the obese (unlike lean people who use FFAs)

ASSESSMENT

History

• dietary history
• any significant gain or loss of weight and whether this change was intentional
• risk factors for enteral failure
  — e.g. changes in gastrointestinal function, prior abdominal or bariatric surgeries, and/or mechanical limitations to eating

Examination (often limited by body habitus)

• CVS, RESP, GI exam
• volume status
• muscle wasting (chronic protein-calorie malnutrition)
• check entire skin surface for integrity and presence of wounds
  — check skin folds carefully
  — may need additional staff / lifting equipment
• determine height and weight accurately -> calculate BMI
  — monitor weight daily, preferably with calibrated bed scale
• 24 hour fluid balance

NUTRITION STRATEGY

High protein hypocaloric enteral nutrition

• enteral feeds preferred
• 60–70% of target energy requirements or 11–14 kcal/kg actual body weight per day
• protein (often 50–60% total calories) at:
  — 2.0 g/kg IBW per day for class I and II obesity (BMI 30-35 and 35-40 respectively)
  — 2.5 g/kg IBW per day for class III obesity (BMI >40)

Rationale

• prevents complications of overfeeding, such as:
  — hyperglycemia (also improves insulin sensitivity)
  — fluid retention
  — increased lipogenesis
  — hepatic steatosis
  — increased CO₂ production, which increases the work of breathing
• preserves fat free mass (FFM)
• promotes steady weight loss

Contra-indications

• if need to avoid high-protein nutrition
  — e.g. progressive renal failure or hepatic encephalopathy
• if full caloric (dextrose) loads  preferred
  — e.g history of hypoglycemia, diabetic ketoacidosis, or severe immunocompromised state

CONTROVERSIES

• High protein hypocaloric enteral feeding approach has not been validated by a high quality RCT
• mild obesity may confer a survival advantage in critical illness, steady weight loss through hypocaloric feeding might negate this

References and Links

LITFL

• CCC – Obesity and trauma
• CCC – Obesity and Critical Illness
• CCC – Complications of Obesity
• CCC – Obesity and Pharmacokinetics
• CCC – Nutrition of the Critically Ill Obese Patient
• CCC – Bariatric patient hot case

Journal articles

• Port AM, Apovian C. Metabolic support of the obese intensive care unit patient: a current perspective. Curr Opin Clin Nutr Metab Care. 2010 Mar;13(2):184-91. Review. PubMed PMID: 20040861; PubMed Central PMCID: PMC3278904.