Math Competency Dimensional Analysis (DA) Patricia Kelliher RN, MS NUR 1020B Office B building

What are the “7 rights” of medication administration?

Resources Cookson, K. (20013). Dimensional analysis: Calculate dosages the easy way. Nursing 2013, (43) 6, on eLearningwww.Nursing2013.com Miller Wilson, K. (2013). The nurse’s quick guide to I.V. drug calculations. Nursing made Incredibly Easy, ?, 1-2 (“online exclusive”) Koharchik, L. and Hardy, E. (2013). As easy as 1,2,3! Dosage calculations. Nursing made Incredibly Easy, ½, on eLearning

Why dimensional analysis to solve dosage calculations problems? QSEN competencies: safety Logical format that can be used for ALL types of calculations – without memorization of formulas – Factors (mL, mg) must be labeled to use the method Rationale: – enhances a conceptual understanding – improves accuracy – and prevents medications dose errors

MA Nursing Core Competencies CCP 2013

Dosage calculation review All dosage calculations have 2 main components: – Medication dosage prescribed by the HCP, 100 mg – Medication concentration via pharmacy, 50 mg/tablet Concentration is NOT a fraction but is set up as a numerator (top) and denominator (bottom) factors and can be flipped Calculations – measure (or labels) in the numerators will cancel out the same units of measure (or labels) in the denominator

Dosage calculation review The goal is to set up the equation to cancel out all the units of measure (labels) NOT needed in the answer – Prescribed: acetaminophen 650 mg PO every 4 hours prn – Supplied: acetaminophen 325 mg tablets – How many tablets? Tablets ? =1 tablet X 650 mg = 650 = 2 tablets 325 mg 325

Dosage calculation steps Determine the unit of measure (label) needed – Tablet ? Place the information with the same label in the numerator (top) position – Tablet = 1 tablet 325 mg Place the information with the same label in the preceding denominator into the numerator position – Tablet = 1 tablet X 650 mg 325 mg Cancel out the label(s) and complete the math (multiply and then divide) Tablet = 1 tablet X 650 mg = 650 = 2 tablets 325 mg 325

Summary Start with the labels needed in the answer Build the calculation until all labels not needed in the answer are cancelled out Perform the arithmetic to determine the correctly labeled answer Round only with the final answer PRACTICE

Know the Conversions metric = increments of 1000 move the decimal point right or left by 3 spaces 1 kg = 1,000 g3.5 kg = 3,500 g 1 g = 1,000 mg0.5 g = 500 mg 1 mg = 1,000 mcg0.25 mg = 250 mcg 1 L = 1,000 mL0.5 L = 500 mL kilogram = gram = milligram = microgram

Conversions continued 2.2 lb = 1 kg 1 grain = 60 mg 1 ounce (oz) = 30 mL

Practice oral medications Prescribed: potassium chloride 30 mEq PO Supplied: potassium chloride 40 mEq / 15 mL ? mL =

Practice oral medications Prescribed: digoxin mg PO Supplied: digoxin 0.25 mg / tablet (tab) ? Tab =

Practice injectable medications Prescribed: nalbuphine 15 mg SC now Supplied: nalbuphine 20 mg/mL ? mL =

Practice injectable medications Prescribed: cefazolin sodium 250 mg IM now Supplied: cefazolin sodium 1 g/3 mL (OR 1000 mg) ? =

Practice basic IV calculations Prescribed: cephalexin 1 gm piggyback every 8 hr Supplied: cephalexin 1 gm in 50 mL D5W (NS) to infuse over 30 minutes All IV infusions are mL/hour ? mL = hr

Practice basic IV calculations Prescribed: regular insulin at 7 units / hr IV Supplied: regular insulin 100 units in 100 mL NS ?

Practice *** basic IV calculations Prescribed: nitroglycerin 5 mcg/minute IV Supplied: nitroglycerin 50 mg in 500 mL NS ?

Practice complex weight-based IV calculations Prescribed: heparin 15 units/kg/hour IV Supplied: heparin 25,000 units/250 mL D 5 W = 100 units/ 1 mL (found on the pharmacy label) Patient weight: 195 lb = _____ kg ?

Practice complex weight-based IV calculations Prescribed: dopamine 3 mcg/kg/minute IV Supplied: dopamine 800 mg in 250 mL NS Patient weight: lb ? Conversion move the decimal point

Practice complex weight-based IV calculations Prescribed: propofol 20 mcg/kg/minute IV Supplied: propofol 15 mg/mL Patient weight: 217 lb ?

Practice 1.Prescribed: nifedipine 30 mg PO daily Supplied: 10 mg tablets Answer _____ 2. Ordered: cefazolin (Ancef) 750 mg (IM) On hand; cefazolin (Ancef) 225 mg / mL _____ 3. meperidine (Demerol) 75 mg IM Stat meperidine 50 mg/mL _____ 4. Ordered: heparin 2500 units SC every 8 hours heparin 5000 units / mL _____

Practice Calculation of gtt/min rates Prescribed: Infuse 125 mL per hour using an IV drip set at 10 gtt/mL. ? gtt = min Reduce the numbers in the set-up when possible.

Practice Calculation of gtt/min rates Prescribed: A 20 gtt/mL set is to be used to infuse at a rate of 90 mL/hr. Calculate the gtt/min flow rate. ? gtt = min

Practice Calculation of gtt/min rates Prescribed: Calculate the gtt/min flow rate to administer an IV at 100 mL/hr using a set calibrated at 15 gtt/mL. ? gtt = min

Practice Calculation of gtt/min rates Prescribed: Calculate the gtt/min flow rate for 100 mL to be infused in 40 min using a set calibrated at 15 gtt/mL. ? gtt = min

Formulas do NOT promote understanding or future retention Basic dosage calculation: D (desired dose) x Q (quantity) ==Dose H (amount on hand) IV drips: 1.Total volume to be infused X drop factor = gtts/min Total time in minutes or hours 2. Drips in units / hour D (desired dose) x V (volume)=units/hour (# mL X units/mL=dose) H (amount on hand)

Next class Continued review of handouts, eLearning