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Source: Kumpf VJ and Chessman KH. Enteral Nutrition. In: DiPiro, JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM. Pharmacotherapy: A Pathophysiologic Approach. 8th ed. http://accesspharmacy.com/content.aspx?aid=8012769. Accessed July 28, 2012.

  • Delivery of nutrients by tube or mouth into gastrointestinal (GI) tract.
    • Focus of entry: delivery through feeding tube.

  • Usable fuels generated through digestion and absorption
    • Digestion: stepwise conversion of complex chemical and physical nutrients via mechanical, enzymatic, and physicochemical processes into molecular forms that can be absorbed from GI tract
    • Absorption occurs across intestinal cell membrane.
      • Nutrients reach systemic circulation through portal venous or splanchnic lymphatic systems.

  • Enteral nutrition (EN) indicated in patients who cannot or will not eat enough to meet nutritional requirements.
    • Requires functioning GI tract
  • Contraindicated with mechanical obstruction and necrotizing enterocolitis.
  • EN success may be challenged with:
    • Severe diarrhea
    • Protracted vomiting
    • Enteric fistulas
    • Severe GI hemorrhage
    • Intestinal dysmotility
  • Advantages of EN over parenteral nutrition (PN):
    • Maintaining GI tract structure and function
    • Fewer metabolic, infectious, and technical complications
    • Lower costs
  • Initiate EN within 24–48 hours of hospitalization for critically ill patients
  • Delay EN until oral intake inadequate for 7–14 days in mild to moderately stressed, well nourished patients.

  • Provide calories, macronutrients, and micronutrients to patients unable to achieve these requirements from oral diet.

  • Enteral access
    • Four routes of administration
      • Indications, tube placement options, advantages, and disadvantages in Table 1.
      • Choice depends on anticipated duration of use and feeding site (stomach vs. small bowel).
  • Administration methods
    • Continuous
      • Preferred for initiation
      • Well tolerated
      • Increased costs due to pump and administration
    • Cyclic
      • Increased mobility due to breaks from infusion system
    • Bolus
      • Commonly used in long-term care residents with gastrostomy tube
      • Minimal equipment and administration time required (5–10 minutes)
      • Potential side effects:
        • Cramping
        • Nausea
        • Vomiting
        • Aspiration
        • Diarrhea
    • Intermittent
      • Similar to bolus except that administration time longer (20–60 minutes)
        • Improved tolerability but more equipment
  • Initiation
    • Optimize achievement of nutrient goals by improved GI tolerance with use of initiation and advancement protocols.
    • Continuous EN feedings
      • Adults: 20–50 mL/hour and advanced by 10–25 mL/hour every 4–8 hours until goal achieved
      • Children: 1–2 mL/kg/hour
      • Premature infants: 10–20 mL/kg/day
    • Intermittent EN feedings:
      • Adults: 120 mL every 4 hours and advanced by 30–60 mL every 8–12 hours
    • Bolus
      • Children: 2–4 mL/kg per bolus with advancement by similar amounts every 4–24 hours
  • Formulations
    • Provide essential nutrients, including macronutrients (e.g., carbohydrates, fats, and proteins) and micronutrients (e.g., electrolytes, trace elements, vitamins, and water).
    • Proteins: molecular form of protein source determines amount of digestion required for absorption within small bowel.
    • Carbohydrates: provide major source of calories.
      • Polymeric entities preferred over elemental sugars.
    • Fat: vegetable oils most common source.
    • Fiber: soy polysaccharides added to some products.
    • Osmolality: function of size and quantity of ionic and molecular particles primarily related to protein, carbohydrate, electrolyte, and mineral content.
      • Adults: 300–900 mOsm/kg (300–900 mmol/kg)
      • Children: <450 mOsm/kg (450 mmol/kg)
  • Classification of EN formulations
    • Based on composition and intended patient population (Table 2)
    • Disease state–specific formulations designed to meet unique nutrient requirements and manage metabolic abnormalities.

Table 1. Options and Considerations in Selection of Enteral Access

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