NAPLEX Question of the Week: Parenteral Nutrition

Parenteral nutrition is part of a pharmacist's daily practice within a number of settings, especially acute care and home care. Today's question focuses on the calculation aspect of parenteral nutrition.

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Mar 12, 2019
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A 55 yo M in the ICU is receiving TPN daily with 400 g of dextrose, 100 g of amino acids, and 250 ml of 10% lipids. How many non-protein calories is the patient receiving from the TPN?  

A. 1510 kcal

B. 1635 kcal

C. 1740 kcal

D. 2035 kcal





Answer and Rationale:

The correct answer is B.

Calculations involving parenteral nutrition are a common part of pharmacy practice. Many pharmacists, especially critical care pharmacists, perform these calculations on a daily basis and are relied upon to determine appropriate nutritional requirements within parenteral nutrition for patients requiring these therapies.

  • The question is asking for non-protein calories so calories from amino acids do not need to be calculated.This makes answer D incorrect as this would be TOTAL calories. Don't miss a question because you assumed the right question...read thoroughly and accurately!
  • Calories from dextrose:
    • Dextrose provides 3.4 kcal/g
    • 400 g X 3.4 kcal/g = 1360 kcal
  • Calories from lipids:
    • 10% of a lipid solution provides 1.1 kcal/ml
    • 250 mls X 1.1 kcal/ml = 275 kcal
  • 1360 kcal + 275 kcal = 1635 kcal which is the correct answer.

For more information on parenteral nutrition, please see our chapter in the NAPLEX 3rd edition:

https://accesspharmacy.mhmedical.com/content.aspx?bookid=2512§ionid=201034086

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Christopher M. Bland

Clinical Associate Professor, University of Georgia College of Pharmacy

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