Dosage Calculations Using Dimensional Analysis Anyone can do it!

Outcomes: Understand the learning components needed for student success in performing dosage calculations. Utilize dimensional analysis to calculate dosage. Potential resources for teaching dimensional analysis in the classroom.

Ways to calculate dosage: Formula Method Amount to Give Challenge: Must remember the extra step of changing D and H to same unit of measurement. Also may have extra variables such as body weight, times per day, etc.

Ways to calculate dosage: Ratio and Proportion Linear Ratio and Proportion Fractional Ratio and Proportion 500mg : 1 tab :: 1 g : x tabs Product of the means equals the product of the extremes. The products of cross multiplication in a proportion are always equal

Dimensional Analysis Dimensional Analysis involves setting up a series of fractions. All information is in one problem Students do not have to remember multiple steps Students ask four simple questions to set up their dimensional analysis problem.

Necessities for Student Success in Dosage Calculations Review of basic math functions – fractions and decimals Adding Subtracting Multiplication Division Students must memorize equivalents

The 4 main questions What is the order? What is on hand? Do you need any equivalents? Where are you going? (or what are you being asked to give?)

Start with conversions 240 mg = ______ grains

Start with conversions 240 mg = ______ grains 4 4 grains 1

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml What is the order?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml What is on hand?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Do you need any equivalents?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Where are you going? (or what are you being asked to give?)

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Begin by cross canceling labels

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Labels left should be “what you are looking for”

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Do the math 1 5 5 2 1

What about problems with different units of measurement? Order: digoxin elixir 0.05 mg PO daily Label: Digoxin 50 mcg per ml How many milliliters will you give? 20 ml 1 1

Complex Problems Order: Augmentin 12.5mg/kg PO every 12 hours. Child weighs 22 lbs. Pharmacy sends a 75 ml bottle of Augmentin labeled 125mg/5ml. How many milliliters will you pour from the bottle? 5 ml

25 What about IV problems? Order: 250ml 5% D/W IV in 2.5 hours. Tubing package reads 15 gtts/ml. How many gtts/min will you adjust the IV? 25

Physicians order Daypro 1200 mg bid. cap 1

Order: Estratab 1250mcg daily

The order reads: Administer 1000cc of D5NS over 10 hrs The order reads: Administer 1000cc of D5NS over 10 hrs. The drop factor on your tubing is 15 gtts/cc. How many gtts/min? 25 1 25 gtts/min 4 or 1

Practice Problems

Your patient may receive Dilaudid 3 mg IM q3h for pain Your patient may receive Dilaudid 3 mg IM q3h for pain. Dilaudid is supplied in 1-ml ampules containing 4 mg. How many milliliters will you administer? ¾= 0.75 ml

The physician orders heparin 2500U subq. You have heparin, 5000U per ml. How many ml will you administer? 1 ml 2

Your patient needs morphine gr 1/6 SQ stat for chest pain Your patient needs morphine gr 1/6 SQ stat for chest pain. You have a 20 ml vial labeled 15mg/ml. How many milliliters will you give? ml 0.67

A patient with tachycardia has an order for Brevibloc to be started at 50 mcg/kg/min. The concentration is Brevibloc 5 g in 500ml of D5W. The patient weighs 176 pounds. How many ml/h should the IV pump be programmed for? 24 ml/hr 1 2 25 12 1 80 24 1 2 40 1 1 1

Resources for teaching Dimensional Analysis IV Calculations site  http://www.geocities.com/Heartland/Valley/3049/iv/clcltns.html  Math tutorials  http://www.utep.edu/nurs4710/tutorials/  IV drip rate problems and dosage calculation problems  http://www.dalesplace.net/iv.htm  

Nursing Math Simplified “Math Magic” Author: Susan Garner Moore ISBN: 0-943202-22-1 53 page book – basics on what they call “Math Magic”

Quick & Easy Dosage Calculations Quick & Easy Dosage Calculations: Using Dimensional Analysis by: Christina Wu Nasrawi, Judith Ann Allender, Maura Conner   Product Details Paperback: 318 pages ; Dimensions (in inches): 0.75 x 10.00 x 8.50 Publisher: W B Saunders; 1st edition (February 15, 1999) ISBN: 0721671330

Clinical Calculation Made Easy Clinical Calculations Made Easy: Solving Problems Using Dimensional Analysis : Softbound By Gloria Craig Edition: Second ISBN: 0-7817-3099-6 Pub Date: February 2001 Pages: 272 Illustrations: 245

Medical Dosage Calculations Medical Dosage Calculations June Looby Olsen, Leon J. Ablon, Anthony P. Giangrasso, Anthony Patrick Giangrasso ISBN: 0805356053 Format: Paperback, 336pp Pub. Date: January 1995 Publisher: Benjamin-Cummings Publishing Company Edition Description: Older Edition

Dimensional Analysis for Meds Dimensional Analysis for Meds Anna M. Curren, Laurie D. Munday ISBN: 076685938X Format: Paperback, 319pp Pub. Date: November 2001 Publisher: Delmar Learning Edition Description: 2ND BK&CDR Edition Number: 2

Dosage Calculations Dosage Calculations : A Simplified Approach Billie Ann Wilson, Billie E. Wilson, With Margaret T. Shannon   ISBN: 083859297X Format: Paperback, 219pp Pub. Date: December 1996 Publisher: Appleton & Lange Edition Description: 3rd Edition Edition Number: 3

Calculating Drug Dosages Calculating Drug Dosages: An Interactive Approach to Learning Nursing Math Sandra Luz Martinez De Castillo, Sandra Luz Castillo, Maryanne Werner-McCullough ISBN: 0803605781 Format: Other Format, 128pp Pub. Date: January 2002 Publisher: Davis F A Edition Description: BK&CD-ROM Edition Number: 1

Work with it and Give it time Try it - You'll like it!!