http://0201.nccdn.net/1_2/000/000/167/1a2/Nutrici--n-Enteral.jpg

McCarthy- Nutrition in the ICU, a vital update!

Today’s special guest speaker, Paul J McCarthy MD, CNSC, is a new addition to the Maryland family. Dr. McCarthy recently practiced at the LSU Health Sciences Center, where he acted as an Assistant Professor of Medicine and Neurosurgery as well as the Assistant Director Neurosurgical Intensive Care Unit. Now he serves his time as an Assistant Professor in the Department of Internal Medicine here at the University of Maryland SOM and had been a constant presence in the MICU. Over his extensive career in medicine, Dr. McCarthy has been a voice of reason when it comes to ICU nutrition. Today he gives us a crash course in everything we need to know to keep our patients healthy and fed!

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

Suggested Reading

  1. McClave SA, Martindale RG, Vanek VW, McCarthy M, Roberts P, Taylor B, Ochoa JB, Napolitano L, Cresci G; A.S.P.E.N. Board of Directors; American College of Critical Care Medicine; Society of Critical Care Medicine. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2009 May-Jun;33(3):277-316. [Pubmed Link]
  2. Seron-Arbelo C, Zamora-Elson M, Labarta-Monzon L, Mallor-Boneta T. Enteral Nutrition in Critical Care. J Clin Med Res. 2013 Feb; 5(1): 1–11. [Pubmed Link]
  3. Marik PE. Enteral nutrition in the critically ill: myths and misconceptions. Crit Care Med. 2014 Apr;42(4):962-9. [Pubmed Link]
About the Author

Jim Lantry

Twitter Google+

Just your average critical care doc: Wandering the ED and ICUs for the USAF down in the San Antonio Military Medical Center, traveling the globe to cannulate for ECLS wherever the need arises, and trying to keep up with great minds of today. E: JlantryMD@gmail.com

Share this Post

Leave a Comment