Presentation on theme: "Dosage Calculation Review"— Presentation transcript:
1 Dosage Calculation Review Review based on required readings selected from:Pickar, G. (2007). Dosage calculation: A ratio-proportion approach (2nd ed.). Albany, NY: Delmar. ISBN
2 Upon completion of this learning activity the student should be able to: Perform ratio proportion to solve equations for “X”.Convert using ratio proportion between systems of measurement as well as within the metric system.Calculate doses based on body weight using ratio proportion.Calculate intravenous drip rates using an IV administration set versus an electronic delivery device.Calculate advanced Intravenous calculations for medicated infusions.
3 How to use this activity: In order to complete this activity you will need the following:CalculatorPractice math testDosage Calculation textbookSelect the action button for the topic you are interested in from the main menu on the next slide…..Lets Begin…
4 Menu: Select from the following options below: Ratio proportionWeight based calculationsParenteral dosesConverting usingratio proportionCalculating IV dripsAdvanced IV calculations
5 Ratio ProportionAccording to Pickar, a ratio proportion is defined as:an equation of two equal ratios that can be expressed as fraction (Pickar, 2007 pg 49)It is used to solve an unknown through the use of cross multiplication and isolating “x” and helps us to solve calculation problems wherein you are provided and prescribed dose and a dosage on hand.
6 Basics of Ratio Proportion Look at the review in Pickar on page 49:Let’s set up an equation where the unknown value is represented by x, and cross-multiplied and simplified to find its value1 = __“x” __4 X “x” = 1 X 84x = 8x = 2Replacing X with 2 in the original equation confirms the answer:1 = _2 _Review set 9 for additional practice on page 49-50
7 Steps for Ratio Proportion Convert to like tags or units of measureIf weight adjusted, calculate the doseIf a continuous IV infusion is prescribed in the order (ex 2 mg/min), calculate dose per hour (ex 120 mg/hr)Set up your ratio proportionDosage on hand = dosage desiredamount on hand “x” amount desiredCross multiplySolve for xLabel xRecheck your answer
8 Ratio Proportion Example Example from practice math sheet:Lopressor 25 mg is ordered and Lopressor 50 mg is provided.50 mg = mgI tablet x tablet50 x = 25X = 0.5 tabletsFor more practice refer to Pickar review set 24 on page 180 and the practice math sheets provided at the college.
9 Converting using Ratio Proportion cont’d Review of common equivalents1mg = 1000 mcg 1 oz = 30 ml1 gm= 1000 mg 1 tsp = 5 ml1 kg = 1000 gm 1 lb = 2.2 kg1 L = 1000 ml1 grain = 60 mg or 65 mgReview of Roman numerals:X = the Roman number for 10V = the Roman numeral for 5XV = the Roman numeral for fifteen
10 Converting using Ratio Proportion: mg/g cont’d Look at page 74 example #1:Solumedrol 500 mg is ordered while 1gram is supplied.This required a conversion. Follow the steps outlined on page 75:Recall the equivalentsSet up the ratio proportion of equivalentsCross multiply and solve for x1000mg = mg__1 gram “x” grams1000x = 500x = 0.5 grams
11 Converting using Ratio Proportion: grain/mg cont’d Look at page 74 example #2:Codeine gr ½ is ordered, Codeine 30 mg is available.This required a conversion. Follow the steps outlined on page 75:Recall the equivalentsSet up the ratio proportion of equivalentsCross multiply and solve for x60mg = mg__1 grain “x” grains60x = 30x = 0.5 grains
12 Converting using Ratio Proportion: mcg/mg cont’d Look at page 83 problem #23:You have 18 mcg and you need to convert to mg.This required a conversion. Follow the steps outlined on page 75:Recall the equivalentsSet up the ratio proportion of equivalentsCross multiply and solve for x1000mcg = 18 mcg__1 mg “x” mg1000x = 18x = mg
13 Converting using Ratio Proportion: lb/kg cont’d Look at page 87 problem #37:The weight is 110 lbs and you need to convert to kg.This required a conversion. Follow the steps outlined on page 75:Recall the equivalentsSet up the ratio proportion of equivalentsCross multiply and solve for x2.2 lb = lbs__1 kg x kg2.2x = 110x = 50 kg
14 Parenteral DosesWhen administering a parenteral dose you will follow the same steps for ratio proportion but recall the rules for rounding when drawing up medication in a syringe as explained on page 202.Round to the nearest tenth when using a 3 ml syringe for a volume greater than 1 mlRound to the nearest one hundredth when using a 1 ml syringe for volumes smaller than 1 ml.If a volume is calculated in tenths, you can draw it up in a 1ml or 3ml syringe.Lets practice…
15 Parenteral dose practice Look at example # 6 on page 206Order: Robinul 150 mcg , Supplied: 0.2mg /ml , What would you administer?First convert:0.2 mg = 1mgX mcg mcg X = 200 mcgNext set up ratio proportion:150 mcg = mcgX ml ml200 x = 150x = mlThen think rules and select equipment before deciding to round:Since the volume is less than 1 ml and the volume is solved to the neared hundredth, select a one ml syringe and no further rounding would be required. X = 0.75 ml is the answer. Review practice questions starting on page 208.
16 Calculating weight based doses Look at examples on page 284, then review the rules:Convert weight first using ratio proportion2.2 lb = lbs1 kg x kg x = 35.9 kgTip always use a calculator so as not to reenter the weight for the next part.Set up ratio proportion for dose (use example on page 285)0.05mg = x mg__1 kg kgCross multiply and solve for x x=1.79 mg
17 Calculating weight based doses practice Administer 0.5 mg/kg of a drug to a client weighing 79 lbs. The vial supplied contains 10 mg/mlConvert weight first using ratio proportion2.2 lb = lbs1 kg x kg x = 35.9 kgCalculate dose by multiplying weight by ordered dose:35.9 X 0.5 mg = mgSet up ratio proportion17.95 mg = 10 mg__X ml mlCross multiply and solve for x x=1.795 mlThink volume and use a 3 ml syringe and round to the nearest tenth. X= 1.8 ml
18 Calculating weight based doses practice 2 Look at problems from the practice math sheet:Administer heparin 64 units/kg to a client weighing 110 lbs rounding to the nearest 100 units. The vial supplied contains units/mlConvert weight first using ratio proportion2.2 lb = lbs1 kg x kg x = 50 kgCalculate dose by multiplying weight by ordered dose:50 X 64 units = 3200 units (no further rounding of dose is required)Set up ratio proportion3200 units = units_X ml mlCross multiply and solve for x x=0.32 mlThink volume and use a 1 ml syringe and round to the nearest hundredth. X= o.32 ml
19 Calculating IV drips Review of formulas: Volume___X drop factor = ratetime in minutesAll administration sets are calculated as gtts/min where the drop factor calibration is provided on the packaging.All electronic delivery devices are calculated as ml/hr with a drop factor calibration of 60.Total ml ordered = ml/hr# of hoursAll that is required is to plug in the values.
20 Using electronic delivery devices All medicated IV drips; heparin, nitroglycerin, dopamine, etc are administered on an IV pump in ml/hr and rounded to the nearest tenthFor IV piggybacks and non medicated IVs round to the nearest whole number.Lets practice…
21 Calculating IV drips practice See page 345:1000 ml D5W over 10 hours on a pump1000ml = 100 ml/hr10 hrsLactated ringers at 150 ml/hr using a 15 drop factor administration setX 15 gtts/ml = gtts/min/ rounded to 38 gtts/min60 minutesContinue practice on page 351 and on your practice math sheets.
22 Advanced IV calculations If weight adjusted, calculate the dose by multiplying prescribed dose by kg weightIf a continuous IV infusion is prescribed in the order (ex 2 mg/min), calculate dose per hour (ex 120 mg/hr)Convert to like tags or units of measureSet up your ratio proportionDosage on hand = dosage desiredamount on hand “x” amount desiredCross multiplySolve for xLabel xRecheck your answer
23 Advanced IV calculation example Heparin is ordered at 12 units/kg/hour to a client weighing 220 lbs. The available IV solution is labeled Heparin units 250 ml D5W. How would you program the pump?If weight adjusted, calculate the dose12 units/kg/hr X 100 kg = 1200 units/hrDon’t need to calculate dose per hour as that is how it is orderedDon’t need to convert to like tags or units of measureContinued
24 Advanced IV calculation example Set up your ratio proportion25000 units = units/hr250 ml x ml/hr25000 x =x = 12 ml/hrIf there was a decimal point it would be rounded to the nearest tenth.Recheck your answer100 units = x units/hr1 ml ml/hrx = 1200 units/hr
25 Additional advanced IV calculation example The client is prescribed Cardizem (Diltiazem) at 5.5 mg/hr. The Cardizem IV solution contains Cardizem 125 mg/125 ml. What does the nurse prepare to administer?The dose is not weight adjusted, so it is unnecessary to calculate the doseDon’t need to calculate dose per hour as that is how it is orderedDon’t need to convert to like tags or units of measureContinued
26 Additional Advanced IV calculation example Set up your ratio proportion125 mg = /hr125 ml x ml/hr125 x =x = 5.5 ml/hrSince this is a medicated drip, it would be rounded to the nearest tenth.Recheck your answer1 mg = x units/hr1 ml ml/hrx = 5.5 mg/hr