McCarthy- Nutrition in the ICU, a vital update!

Clinical Pearls (special thanks to Dr. Meagan Pate) 

• Malnutrition
  • Definition: “An acute, subacute or chronic state of nutrition, in which a combination of varying degrees of over-nutrition or under-nutrition with or without inflammatory activity have led to a change in body composition and diminished function”
  • Diagnosis requires two of (from ASPEN website):
    • Insufficient energy intake
    • Weight loss
    • Loss of muscle mass
    • Loss of subcutaneous fat
    • Fluid accumulation that may mask weight loss
    • Diminished functional status as measured by hand-grip strength
  • Importance
    • 1/3 of hospitalized patients
    • Results in 3x longer hospital LOS
    • Surgical patients have 4x higher risk of pressure ulcers
    • Greater overall mortality
  • 3 broad categories
    • Starvation-related, e.g. anorexia nervosa
    • Chronic disease-related, e.g. cancer
    • Acute disease- or injury-related, e.g. trauma
• Nutritional screening
  • ASPEN / SCCM guidelines state that patients should be screened for malnutrition within 24-48 hours of hospital admission
    • Recommendations use either NRS-2002 or NUTRIC score (>5 = enteral nutrition)
  • Current scores aren’t perfect (require many variables, aren’t easy to use); thus there are emerging tools, e.g. dietician physical exam, CT scans of various muscles
  • Other screening markers are of little value!
    • Albumin, pre-albumin, transferrin, procalcitonin, CRP, IL-1, TNF
    • IL-6 may have some merit
• Enteral nutrition
  • Enteral nutrition is typically favored over parenteral
    • Supports gut integrity
    • Decreases infection risk
    • Improved outcomes
    • Decreases hospital LOS
  • Disadvantages
    • Requires gut function
      • However, no data (and not in SCCM guidelines) to say that bowel movements or bowel sounds are required for enteral nutrition
    • More difficult to control calories
    • Access
  • Post-pyloric
    • Trials tend to show decreased risk
    • Mixed results on calories delivered
    • Takes longer to get caloric goals
    • No decrease in mortality
    • Recommendations are to initiate in stomach, then divert to lower in GI in intolerant or high risk
  • Formula selection
    • Start with standard polymeric formula
    • Rarely need disease-specific formula, e.g. hepatic, renal, pulmonary
  • When and how much?
    • If unable to tolerate oral diet in 24-48 hrs, hemodynamically stable, and NUTRIC > 5, there is benefit to start nutritional support (NO BENEFIT otherwise!)
      • If low nutritional risk, no benefit of EN in first week
    • Trophic or full feeds appropriate for ALI/ARDS and patients expected to be on MV > 72 hours, advancing to goal over 24-48 hours (provide > 80% of needs)
  • Monitoring
    • Should we monitor? Critically ill patients not getting 80% of caloric goals for 48hrs have 80% mortality vs those that tolerate feeds have 20% mortality
      • However, gastric residual volumes are not part of routine care to monitor ICU patients (if you must check, aim for <500)
      • Do not interrupt for diarrhea
    • Always assess for risk of aspiration and PNA
• Parenteral nutrition
  • Advantages
    • GI function not needed
    • Can control caloric intake
  • Disadvantages
    • Infection risk
    • Access
    • Monitoring
    • Cholestasis (long-term)
    • Cost
  • When and how much?
    • For those with low nutrition risk, hold PN for the first 7 days following ICU admission
    • High nutrition risk or severely malnourished and unable to get EN, start PN as soon as possible
    • Either low or high, consider supplemental PN after 7-10days if unable to meet 60% of energy and protein requirements by EN
• Goals of nutrition
  • How to determine caloric needs
    • Indirect calorimetry
      • Based on O2 consumption and CO production
      • Not very practical
    • Weight-based equation (25-30 kcal/kg/d) – true weight (not IBW)
      • More practical
      • Tends to be fairly accurate
    • Limit restrictions in most
  • Protein
    • Almost never need to restrict; higher protein in many cases, e.g. sepsis, RRT
    • 1 – 2.5 g/kg IBW/d
    • Several observational studies have shown protein intake related to outcomes
      • Patients may tolerate fewer calories, but not less protein
      • “Permissive underfeeding with full protein was associated with similar outcomes in both high and low nutritional risk patients”
• Refeeding syndrome
  • Delivery of carbohydrate calories in malnourished
    • Insulin causes intracellular shift of electrolytes
      • Hypophosphatemia
      • Hypokalemia
      • Hypomagnesaemia
  • Clinical
    • Muscle weakness
    • Edema
    • Arrhythmia
    • Hemolysis
  • Treatment
    • Identify at risk patients
    • Plasma electrolytes, in particular Na, K, phos, and Mg should be monitored before and during re-feeding (replete)
    • Thiamin (IV), MVI, +/- folate
    • Calorie repletion should be slow at 10 – 20 kcal/kg/day or, on average, 1000 kcal/d initially
• Glucose management
  • Benefit of an insulin infusion due to anti-inflammatory properties
• Adjunctive therapies
  • Soluble fiber: routine for non-surgical patients
  • Protein: supplement to meet protein goals
  • Probiotics: no harm
  • Antioxidants: no harm
  • Glutamine: no harm, some benefit in burn patients
• Special substrates
  • Trauma
    • Arginine (LOS, infection)
    • Fish oil (LOS, infection)
  • Open abdomen
    • EN 24 to 48 hours
    • Provide 15 – 30 gram extra protein per liter exudate
  • Burns
    • Protein: 1.5 to 2 gram/kg
    • Initiate VERY early EN (4 – 6 hours)
  • Post-operative
    • Start regular diet (no data supporting clears first)
    • Use PN after day 5 if EN not feasible
    • Consider probiotics
  • Sepsis
    • Start EN within 24 – 48 hrs. after hemodynamically stable
    • PN should be avoided during first week (regardless of caloric needs)
    • Start with trophic, increase to goal within week
    • 1.2 – 2 g protein/kg/day
    • Immune modulating supplements may not be beneficial
      • Arginine is safe
  • Pancreatitis
    • No strong data to support probiotics
    • Should delay PN if patient nourished
      • Mild case PO bland diet
      • Moderate to severe, early enteral
    • Minimal benefit to small bowel feeds
  • Ileus
    • NPO can cause ileus
    • Trophic EN can improve
    • Early post-operative EN can decrease ileus
    • If EN not possible for 7 days consider PN
  • End of life
    • Basically: not obligated to feed these patients
  • HD unstable
    • EN should be withheld until the patient is fully resuscitated and/or stable
    • EN may be considered with caution in patients undergoing withdrawal of vasopressor support
  • Therapeutic hypothermia
    • Pros: Energy source, infection prevention
    • Cons: Free radicals, generates heat, decreased caloric needs, hyperglycemia