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Chapter 9: Special Types of Intravenous Calculations

Chapter 9: Special Types of Intravenous Calculations. Intravenous Calculations. These are very potent medications. Small changes infusion rate can greatly affect body’s physiologic response. Pharmacy usually prepares medications and IV solutions. Dosage Calculations.

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Chapter 9: Special Types of Intravenous Calculations

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  1. Chapter 9: Special Types of Intravenous Calculations

  2. Intravenous Calculations • These are very potent medications. • Small changes infusion rate can greatly affect body’s physiologic response. • Pharmacy usually prepares medications and IV solutions.

  3. Dosage Calculations • D = Desired dose or order • H = On hand or have • S = Supply

  4. Three Methods of Dosage Calculation • Proportion expressed as two fractions • Proportion expressed as two ratios • Formula method

  5. Proportion Expressed as Two Fractions • SUPPLY = X HAVE DESIRE

  6. Proportion Expressed As Two Ratios • SUPPLY : HAVE :: X : DESIRE

  7. Formula Method • DESIRE x SUPPLY = X HAVE

  8. Infusion Rates Formulas • Amount of Drug = Amount of Drug in 1 mL Amount of Fluid (mL) • Total number of units/hour x X mL= mL/hour Number of units to run • Total number of mg/hour x X mL= mL/hour Number of mg to run • Total number of milliters ordered = hours Total number of milliters/hour

  9. Question The physician has ordered regular insulin 21 units/hour IV. The medication is available 250 units in 250 mL normal saline. The insulin IV is being run on an infusion pump. What is the rate per hour? A. 19 B. 20 C. 21 D. 22

  10. Answer C. 21 Total number of 21 units/hour x 250 mL= 21 mL/hour Number of 250 units to run

  11. Infusion Formula for Drugs Ordered in mcg/min • Reduce the numbers in the standard solution to mg/mL. • Change mg to mcg. • Divide by 60 to get mcg/min. • Use either the formula, ratio, or proportion method to solve for mL/hr.

  12. Infusion Formula for Drugs Ordered in mcg/kg/min • Reduce the numbers in the standard solution to mg/mL. • Change mg to mcg. • Divide by 60 to get mcg/kg/min. • Use either the formula, ratio, or proportion method to solve for mL/hr.

  13. Question The physician has ordered Intropin (dopamine) 200 mcg/min IV. The medication is available 400 mg in 250 mL D5W. What is the rate in mL/hr? A. 7 mL/hr B. 7.5 mL/hr C. 8 mL/hr D. 8.5 mL/hr

  14. Answer B. 7.5 mL/hr • Reduce the numbers in the standard solution to mg/mL: 400 mg/250 mL = 1.6 mg/mL. • Change mg to mcg: 1.6 mg x 1000 = 1600 mcg/mL. • Divide by 60 to get mcg/min: 1600 mcg/60 min = 26.67 mcg/min. • Use either the formula, ration, or proportion method to solve for mL/hr: 200 mcg/min x 1 mL/hr= 7.5 mL/hr 26.67 mcg/min

  15. Body Surface Area • Antineoplastic drugs based on body surface area in square meters • Mathematical formulas • Square root of weight (kg) X height (cm) = BSA 3600

  16. Body Surface Nomogram • Mark the client’s height in first column. • Mark the client’s weight in the third column. • Draw a line between these two marks. • Point at which the line intersects in the middle column indicates estimated body surface in meters squared.

  17. Body Surface Nomogram

  18. Patient Controlled Analgesia • Basal rate: amount of medication infused continuously every hour • PCA dose: amount of medication infused when the client activates the button control • Lockout time or delay: interval during which patient cannot initiate another dose after giving a self dose; prevents overdosage • Total hourly dose: maximum amount of medication the client can receive an hour

  19. Heparin and Insulin Protocols • Protocols are based on a parameter, usually a lab test ordered by healthcare provider • After receiving the lab test results, the nurse uses the protocol to determine the change in the dosage amount.

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