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Chapter 38. Parenteral Nutrition

LC is a 48-year-old man who underwent small bowel resection for a volvulus (gut twisting) that caused bowel necrosis. He is receiving PN and has required a nasogastric tube for suction. He develops metabolic alkalosis. Which of the following is the most appropriate adjustment to LC’s PN solution?

a. Add sodium bicarbonate

b. Decrease acetate and increase chloride

c. Increase acetate and decrease chloride

d. Increase sodium and potassium

Answer b is correct. Acetate in PN solutions tends to have an alkalinizing effect (because of its conversion to bicarbonate in the liver), whereas chloride has an acidifying effect. Therefore, decreasing acetate and increasing chloride should help to improve a metabolic alkalosis.

Answer a is incorrect. Sodium bicarbonate is generally not added to PN solutions due to compatibility issues. When a source of base is desired to be added to a PN solution, acetate is usually utilized. Acetate is converted to bicarbonate in the liver. Adding sodium bicarbonate to a PN solution would tend to worsen a metabolic alkalosis rather than to improve this condition.

Answer c is incorrect. As explained above for Answer b, increasing acetate and decreasing chloride in a PN solution might be helpful in correcting a metabolic acidosis, but it would be expected to worsen a metabolic alkalosis and would therefore be inappropriate for a patient with metabolic alkalosis.

Answer d is incorrect. Not enough information is given to determine whether increasing sodium in the PN is appropriate for this patient, and these changes would not directly affect acid-base balance. Fluid overload can be a problem in some PN patients, and excess sodium in the PN could exacerbate this problem. The amount of the potassium in the PN should not generally affect acid-base balance.

A patient is receiving ProcalAmine postoperatively at 100 mL/h. ProcalAmine contains 3% final concentration of glycerin (4.3 kcal/g) and 3% final concentration of amino acid. How many total calories and how much protein are provided per day by this solution?

a. 598 kcal and 72 g amino acid

b. 533 kcal and 72 g amino acid

c. 720 kcal and 60 g amino acid

d. 747 kcal and 60 g amino acid

Answer a is correct. Calculation of kcal and amino acid is as follows:

100 mL/h × 24 h/d = 2400 mL/d

Glycerin provides 4.3 kcal/g

3 g glycerin/100 mL = x g glycerin/2400 ...

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