Chapter 9 Special Types of Intravenous Calculations

1. Chapter 9Special Types of Intravenous Calculations

2. Intravenous Calculations • Very potent medications • Small changes in 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× 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 mL= mL/hour Number of units to run • Total number of mg/hour× X mL= mL/hour Number of mg to run • Total number of milliliters ordered = hours Total number of milliliters/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/hour× 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 the formula, ratio, or proportion method to solve for mL/hour

12. Infusion Formula for Drugs Ordered in mcg/kg/min • To convert lb to kilograms, divide by 2.2 • Reduce the numbers in the standard solution to mg/mL • Change mg to mcg • Divide by 60 to get mcg/min • Use the formula, ratio, or proportion method to solve for mL/hour

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

14. Answer B. 7.5 • 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 × 1000 = 1600 mcg/mL • Divide by 60 to get mcg/min: 1600 mcg/60 min = 26.67 mcg/min • Use either the formula, ratio, or proportion method to solve for mL/hour 200 mcg/min x 1 mL/hour = 7.5 mL/hour 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) × height (cm) = BSA 3600

16. Body Surface Nomogram • Mark the patient’s height in first column • Mark the patient’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 patient activates the button control • Lockout time or delay: feature that sets interval during which patient cannot initiate another dose after giving a self dose • Total hourly dose: maximum amount of medication the patient can receive in 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