Conversions Metric and Household Systems Conversion Slide Use

Conversions: Metric and Household Systems

Conversion Slide • Use this diagram when converting dosages within the metric system • Move the decimal place three places for each step! kg g mg mcg 2

Common Conversions Weight: 1 kg = 2. 2 lbs 1 lb = 16 oz Length: 1 inch = 2. 54 cm For weight and height ALWAYS round to the tenths if there is a whole number and hundredths if there is no whole number! 3

Volume: • • • 5 m. L = 1 t 15 m. L = 3 t = 1 T 30 m. L = 6 t = 2 T = 1 fl oz 240 m. L = 1 cup = 8 fl oz 480 m. L = 2 cups = 1 pint = 16 fl oz 1000 m. L (1 L) = 4 cups = 1 qt = 32 fl oz 4

Problems • • Convert the following: 2 t ____m. L 30 m. L ____T ½ oz ____m. L 20 m. L ____t ½ c _____oz ____m. L 24 oz _____m. L 1. 5 L_______m. L 5

• • 22 in ____cm 65 in ____cm 156 cm ____in 84. 5 cm ____in • • • 25 kg _____lb 3500 g ______kg 185. 6 lb _____kg 59. 5 kg _____lb 1. 2 kg ______g 6

Problems • • • 25 mg _______mcg 125 mcg _______mg 5 g ____mg 125 g _______mcg 0. 125 mcg _______g 37. 5 mg _______g 7

Dosage Calculations • In dosage calculations, you need 3 pieces of information: – The doctor’s or healthcare provider’s order – The quantity or strength of drug on hand – The solid or liquid form of the supply drug • Find a method that works for you – Three-step approach (formula method) – Ratio/Proportion • Expressed as ratios or fractions 8

Three Steps to Dosage Calculations Formula Method • Step 1. Convert – Ensure all measurements are in the same system of measurement and the same size unit of measurement. – If not, convert before proceeding. • Step 2. Think – Estimate what is a reasonable amount of the drug to be administered. 9

Three Steps to Dosage Calculations Formula Method Step 3. Calculate Apply the formula 10

Ratio: Proportion What you have : What you need Dosage on hand = Dosage desired Amount on hand X amount desired Supply = Dosage Have X amount 11

Three Step Approach Doctor’s order: Aricept 10 mg po daily • Convert – No conversion is necessary. Units are in same system (metric) and the same size (mg). • Think – Wanting to give 10 mg and you have 5 mg in each tablet. You want to give twice the equivalent of each tablet or 2 tablets per dose. 12

Doctor’s order: Aricept 10 mg po daily Step 3 -Calculate: Ratio/Proportion: 13

Ordered: Flagyl 0. 75 g po tid How many tablets per dose should be administered? Convert Think Calculate 14

Ordered: Flagyl 0. 75 g po tid How many tablets per dose should be administered? Convert: 0. 75 g to mg = 750 mg Think: Am I going to give more or less than I have on hand? Calculate: 15

Problem The physician ordered Amoxil (amoxicillin) 0. 5 g p. o. q 8 h. Available is Amoxil (amoxicillin) oral suspension 250 mg/5 m. L, total volume of bottle is 180 m. L. a. How many m. L of Amoxil will you administer? 2 _____ t 10 m. L or _____ b. How many full doses are available? ______ 18 c. If the physician’s order is for 5 days, is this an adequate total volume? _____ Yes, 30 m. L x 5 days = 150 m. L

IV Flow Rate • Ordered by physician • Nurse’s responsibility to regulate, monitor, and maintain flow rate • 2 definitions: – m. L/hr – an infusion pump – gtt/min – manually counted (watch count)

Formulas Made Easy! Pump: m. L/h • > 1 hr: total m. L = m. L/hr total hr • < 1 hr: total m. L x 60 min/hr = m. L/hr total min Drops per Min: gtt/min • total m. L x drop factor gtt/m. L = gtt/min total min

Calculation of IV Flow Rate: m. L per hour • Order reads: D 5 W 250 m. L IV over the next two hours by infusion pump 19

• Use one of the formulas: Volume Ratio/Proportion Time Therefore, set pump at 125 m. L per hour 125 m. L/h

IV Flow Rate in m. L per hour: Infusion Rate is less than 1 hour (rounded to a whole number) 21

Calculation of m. L per hour: Infusion Rate is less than 1 hour • Order: – Ampicillin 500 mg IV in 50 m. L D 5 NS in 30 min by infusion pump 22

• Calculate

Manually Regulated IVs • If an infusion pump is not used, the nurse must calculate the ordered IV rate • Based on the number of drops per minute (gtt/min) • The gravity flow rate depends in the IV tubing calibration called the drop factor (gtt/m. L) • Answer MUST be in a whole number! 24

Drop Factors • The drop factor is the number of drops per milliliter (gtt/m. L) that an IV tubing set will deliver • Standard or MACROdrop IV tubing has a drop factor of 10, 15, or 20 gtt/m. L • MICROdrop IV tubing has a drop factor of 60 gtt/m. L – used for infusion pumps 25

IV Flow Rate: Drops per min • Formula for IV flow rate for manually regulated IVs ordered in m. L per hour or for minutes Volume (m. L) Calibration or drop factor (gtt/m. L) Time (min) Rate (gtt/min)

Formula for Infusion Time gtt/min Total m. L x drop factor gtt/m. L = gtts/min Time (in minutes) Example: 1000 m. L NS to run over 12 hours Tubing is 15 gtt/m. L = 20. 8 = 21 gtt/min 1000 ml x 15 gtt/m. L over 720 min = 15000/720 =15, 000 divided by 720 = 20. 8 = 21 gtt/min

Calculation of gtt/min from m. L/hr • Physician orders: – D 5 W IV at 125 m. L per hour • Infusion set is calibrated for a drop factor of 10 drops per m. L • Calculate IV flow rate in drops per min

Calculation of gtt/min from m. L/hr Notice that the m. L and hr cancel out, leaving drops per min 125 m. L/hr x 10 gtt/m. L = 20. 8 gtt/min 60 min/hr Use your watch to count drops and adjust roller clamp to deliver 21 drops per min

IV Calculations Heparin, Insulin & other meds

Concentration Definition Ø Concentration = Total Amount of Drug Total Volume (m. L) Ø Weight over volume: W V

Problem • An order is written for 25, 000 units of heparin in 250 ml of D 5 W to infuse at 1000 units/hr, what is the correct rate of the infusion (in ml/hr)? • Ordered per hour X Quantity (m. L) Have 1, 000 units/hr 25, 000 units X 250 m. L D 5 W

Problem • Heparin sodium 25, 000 units in 250 ml D 5 W and infuse at 2000 units/hr. How many m. L/hr will the pump be set ? • What is the concentration? 25, 000 units 250 m. L • 100 units/m. L • What is the flow rate: 2000 units/h 100 units/m. L • 20 m. L/h

Problem • Mr. Collins has an order for heparin 250 ml bags containing 25, 000 units to run at 800 units/hr. At what rate will the nurse set the infusion pump to deliver the dosage? Ø 8 m. L/h

Insulin • Doctor's order: Regular insulin 50 units in 250 m. L NS to infuse at 7 units/hr • What is the concentration? ______ Ø 0. 2 units/m. L • What is the IV flow rate to deliver this dosage? Ø 35 m. L/h

Insulin • Doctor's order: Regular insulin 50 units in 100 m. L NS to infuse at 12 units/hr. • What is the concentration? _____ Ø 0. 5 units/m. L • The IV flow rate to deliver this dosage is: Ø 24 m. L/h

Potassium Chloride • Order: KCl 40 m. Eq/L D 5 W to infuse at 2 m. Eq/h • What is the concentration? ______ Ø 40 m. Eq/1000 m. L = 0. 04 m. Eq/m. L • Rate for infusion pump: _______ Ø 50 m. L/h______