Nutrition

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CHAPTER 27 Nutrition

I. Definition

A. Nutrition is the provision of the materials necessary to nourish the body and sustain life (Box 27-1).
B. Malnutrition is the lack of adequate intake of nutrients induced by altered dietary intake or nutrient utilization resulting from consuming too little food, lack of vital nutrients, or impaired absorption or metabolism due to disease.

1. Type

a. Marasmus

1) Reduced calorie intake
2) Extremely thin/emaciated; skin hangs on skeletal bones

b. Kwashiorkor

1) Lack of protein intake
2) Fat stores in the abdomen and face

II. Types of Delivery of Nutritional Support

A. Enteral nutrition
B. Parenteral nutrition

1. Peripheral parenteral nutrition (PPN)
2. Total peripheral nutrition (TPN)

III. Enteral Nutrition

A. Involves the gastrointestinal tract and requires a functioning small intestine
B. Oral or feeding tube

IV. Parenteral Nutrition

A. Parenteral nutrition is the use of intravenous nutrients. Patients with a nonfunctioning gastrointestinal tract receive therapy to ensure they are adequately nourished.
B. Goals

1. Maintain or restore nutritional integrity
2. Restore the body’s protein metabolism
3. Prevent malnutrition
4. Diminish rate of weight loss/maintain body weight
5. Promote wound healing
6. Replace nutritional deficits

C. Indications

1. Short bowel syndrome, massive bowel resection
2. Active inflammatory disease of the intestine
3. Severe malabsorption
4. Intractable vomiting or diarrhea
5. Severe acute pancreatitis
6. High output fistula (>500 mL/day)
7. Severe malnutrition with intolerance to enteral tube feedings
8. Enteral feeding access not possible due to upper GI obstruction
9. Enterocutaneous fistula with high output
10. Lower birth weight infants (premature)
11. Bone marrow transplant with graft versus host disease (GVHD) of the gut

D. Contraindications

1. Functional gastrointestinal tract
2. Patients do not want to eat
3. Venous access is not available
4. Awaiting flatus or bowel sounds after surgery
5. Expected duration of parenteral nutrition is less than 5 days
6. Terminal illness

a. The prognosis does not warrant the use of nutritional support (the benefits do not outweigh the risks).

E. Administration

1. PPN

a. Use of small veins in the extremities
b. Used when central line access is not available
c. Short-term use only
d. Osmolarities greater than 900 mOsm/L may irritate the peripheral vein.

1) PPN solutions must be isotonic to prevent damage to veins.

e. Glucose concentration of PPN is lower than that of central TPN.
f. Do not use in patients requiring fluid restrictions.

2. Central (TPN)

a. Use of larger veins in the trunk

1) Subclavian, internal jugular, and femoral

b. Osmolarity generally 1000–2000 mOsm/L

F. TPN components

1. Carbohydrates (dextrose)

a. Caloric value 3.4 kcal/gm
b. Maximal carbohydrate utilization

1) 4–5 mg/kg per minute; do not exceed 7 mg/kg per minute or 202–205 kcal/kg per day

c. Common dextrose TPN concentrations: 5%, 10%, 15%, 20%, 35%

2. Fats (lipid emulsion [Intralipids, Liposyn])

a. Caloric value 9 kcal/g
b. Most concentrated source of calories
c. Fat emulsions available: 10% (1.1 kcal/mL) or 20% (2.0 kcal/mL)
d. Liposyn

1) Prevents fatty acid deficiencies
2) Contains 5% safflower oil, 5% soybean oil, up to 1.2% egg phospholipids
3) In a 10% solution, each mL provides 1.1 kcal
4) Emulsion appears cloudy, with a milky appearance

e. Patients with severe egg allergies may not tolerate lipids

3. Protein (amino acids)

a. Caloric value 4 kcal/g
b. Restrict in patients with end stage renal and/or liver disease
c. Protein requirements increase depending on health of patient

1) Normal: 1 g/kg per day
2) Mild stress: 1.3 g/kg per day
3) Moderate stress (major surgery): 1.5 g/kg per day
4) Major stress (major trauma or burns): >2.0 g/kg per day

e. Ideal amino acid solution is 50:50 ratio of essential to nonessential amino acids.
f. Nitrogen balance studies dictate appropriate protein intake in critically ill patients.

1) N2 balance = N2 intake − N2 loss
2) N2 intake = grams protein consumed/24 hours/6.25
3) N2 loss = grams urine urea nitrogen + 4 (nonurinary losses)

(a) Positive N2 balance between +2 and +4 is optimal.

4. Water (30 mL/kg per day)
5. Vitamins

a. Fat-soluble vitamins: A, D, E, K
b. Water-soluble vitamins: e.g., Vitamins B1, B2, B6, B12

6. Trace minerals

a. Examples: zinc, copper, chromium, manganese and selenium

7. Electrolytes

a. Recommended maximum electrolyte concentrations per liter of standard TPN

1) Na: 130 mEq
2) K: 80 mEq
3) Mg: 8 mEq
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