Medication Calculations in N ursing.pptx

nurs

1. Medication C alculations in Nursing

2. Medication administration is a core competency for all nurses in every clinical setting. A key skill required to safely dispense drugs is the ability to perform accurate dosage calculations. New technologies such as bar code administration and smart infusion pumps have helped to reduce medication errors, however nurses cannot rely completely on these advances. INTRODUCTION

3. When calculating how much of a drug is required , applying the dosage formulas helps in the accuracy of the dose calculation.

4. Overview Metric Conversions Dose Conversion s Infusion Rates

5. Metric Conversions Metric weights and measurements involve a step-by-step conversion from one unit to another. With weight we often convert to smaller (and more numerous units) thus: Kg ------gm ------mg ------mcg Kilo grams grams milligrams micrograms

6. Each of these steps involves the heavier unit being multiplied by 1000 to bring up the number of the smaller units for the same weight .

7. Metric C onversions Kg → g 1kg X 1000 = 1000 gm g → mg 1g X 1000 = 1000 mg 1mg X 1000 = 1000 mcg mg→mcg

8. Metric Conversions If we are converting from a lighter unit to a heavier unit we move the decimal point three places to the left for each conversion

9. Metric Conversions mcg → mg 1000 mcg /1000 = 1mg mg→gm 1000mg / 1000 = 1gm 1000gm / 1000 = 1kg gm→kg

10. Example If we are moving across two conversions we repeat the process twice. For example from grams to micrograms e.g., 2 gm converted to micrograms Step one: = 2 gm x 1000 = 2,00 mg Step two: = 2,000 mg x 1000 = 2 ,000,000 mcg

11. When we are converting volumes the process is the same. Liters → 1000 ml

12. Here we will study several drug calculation methods. The first technique is the universal formula or the “desired over have” method. Universal Formula (Toney-Butler, 2021) In the universal formula (or “desired over have method”), the desired amount (D) is the dose  prescribed and the amount on hand (H) or the amount you “have” is the available dose or concentration. The quantity (Q) is the form and amount in which the drug is supplied (i.e. tablet, capsule, liquid).

13. To calculate the dose, take the desired amount and divide it by the amount on hand, then multiply it by the quantity, like below

14. Examples Oral Dose Cephalexin 750 mg P.O. every 12 hours is ordered. The pharmacy stocks 250 mg tablets. How many tablets should be administered per dose?

15. QUIZ Oral Dose Drug XYZ 500 mg P.O. every 6 hours is ordered. The pharmacy stocks 250 mg tablets. How many tablets should be administered per dose? 2. Drug XYZ 1000 mg P.O. every 8 hours is ordered. The pharmacy stocks 200 mg tablets. How many tablets should be administered per dose?

16. Intravenous (IV) Dose An order for digoxin 0.5 mg IV daily is placed. Digoxin 0.25 mg/mL is available from the pharmacy. How many mL will you need to administer?

17. A patient requires 4 mg of Morphine IV. Morphine is available as 10 mg/ml. How many mls will you draw up? 4 mg / 10 mg x ml = 0.6 ml

18. QUIZ Administer heparin 5,000 units intravenously. Available is heparin 10,000 units/ml. How many ml will you need to administer? Administer heparin 2,000 units intravenously. Available is heparin 5,000 units/ml. How many ml will you need to administer?

19. Subcutaneous Dose Injection Heparin 7500 units subcutaneous every 12 hours is ordered. The pharmacy provides a heparin vial with a concentration of 5000 units/ mL. How many mL will you need to administer?

20. INTRAMUSCULAR D0SE Physician has ordered injection meperidine 20mg for a patient every 4 hours whenever necessary for pain management. Available dose of this drug is 40mg/ml. How many ml will you give for each dose? D/H=20/40×1mL=0.5ml.

21. Dose Conversion ( mg/kg) W e need to check the dose of a drug or solution that is based on the patient’s weight. BW: Body Weight Total dose = prescribed dose x patient’s weight

22. Prescribed dose 10 mg per kg Patient’s weight-66 kg What is the required dose ? mg / kg Dose Conversion 10 mg x 66 kg = 66 mg = 0.660 gm

23. How to Calculate IV Flow Rate?  To calculate IV flow rates, the nurse must know the total volume of fluid to be infused and the specific time for the infusion.  Intravenously administered fluids are prescribed most frequently based on milliliters per hour The volume per hour prescribed is administered by setting the flow rate, which is counted in drops per minute.  There are three commonly used ways on how to indicate flow rates: o Milliliters per hour (mL/h) . Calculated by dividing the total infusion volume by the total infusion time in hours

24. Number of drops per one (1) minute (gtts/min). Calculated by multiplying the total infusion volume to the drop factor and then dividing by the total infusion time in minutes. Infusion time. Total volume to infuse divided by milliliters per hour being infused. Drop factor (sometimes called drip factor). The total number of drops delivered per milliliters of solution. This rate varies by brand and types of infusion sets and are printed on the package of the infusion set. Generally, macrodrops have a drop factor of 10, 12, 15, or 20 drops/ mL. Microdrip sets, on the other hand, have a drop factor of 60 drops/ mL.

25. FORMULA FOR CALCULATING MILLILITERS PER HOUR (mL/hour)

26. To calculate infusion rates for infusions to be administered through a smart pump, the previous discussed formula is used

27. A patient is prescribed Sodium Chloride 1000 ml to be infused over an 8-hour period. A standard giving set is being used. Calculate the drops per minute. 1000 ml × 20 (gtts/min) = ? 480 min

28. References Dodds, K.G. (2012). Safety in Numbers–Essential Calculations for Nurses. Palmerston North. Dunmore Press Ltd. Christchurch Hospital Department of Nursing Drug Calculation Prompt Card (15/06/00) Koharchik , L.S. & Hardy, E.C. (2013). As easy as 1, 2, 3! Dosage calculations. Nursing Made Incredibly Easy! , 11(1), 25 – 29. Toney-Butler, T.J. & Wilcox. L. (2021, March 7). Dose Calculation Desired Over Have Formula Method. StatPearls . https://www.ncbi.nlm.nih.gov/books/NBK493162/ Wilson, K.M. (2013). The nurse’s quick guide to I.V. drug calculations. Nursing Made Incredibly Easy!, 11(2), 1 – 2.

29. Thank You!