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# Res 246 ch 2

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### Res 246 ch 2

1. 1. Metric system andDrug Dose Calculations Ch 2
2. 2. Base Units Kilo Hecto deca Liter, meter, or gram Deci Centi milli
3. 3. Common units of measurements <ul><li>Volume </li></ul><ul><li> 1 L = 1000 mL </li></ul><ul><li>1 mL = 0.001 L </li></ul><ul><li>Weights </li></ul><ul><li>1 Kg = 1000 g </li></ul><ul><li>1 g = 0.000 Kg </li></ul><ul><li>1 g = 1000 mg </li></ul><ul><li>1 mg = 0.001 g </li></ul>
4. 4. 500 mls is equal to how many liters? <ul><li>50 </li></ul><ul><li>5 </li></ul><ul><li>0.5 </li></ul><ul><li>2.5 </li></ul>
5. 5. 450 mls is equal to now many liters? <ul><li>45 </li></ul><ul><li>0.45 </li></ul><ul><li>4.5 </li></ul><ul><li>2 </li></ul>
6. 6. How many grams are equal to 50 kg’s? <ul><li>500 </li></ul><ul><li>5000 </li></ul><ul><li>50000 </li></ul><ul><li>0.05 </li></ul>
7. 7. How many mls in 2 liters? <ul><li>200 </li></ul><ul><li>0.2 </li></ul><ul><li>2 </li></ul><ul><li>2000 </li></ul>
8. 8. How many kg’s in 3500 gms? <ul><li>350 </li></ul><ul><li>35 </li></ul><ul><li>3.5 </li></ul><ul><li>0.35 </li></ul>
9. 9. <ul><li>Drops – only use dropper calibrated specifically for that particular medicine (one from manufacturer) </li></ul><ul><ul><ul><li>16 gtts = 1 ml = 1 cc </li></ul></ul></ul><ul><li>Only use measuring spoons not “eating” spoons </li></ul><ul><ul><ul><li>1 tsp = 5 mL </li></ul></ul></ul><ul><ul><ul><li>1 Tbs = 15 ml </li></ul></ul></ul>
10. 10. <ul><li>1 inch = 2.54 cm </li></ul><ul><li>2.2 lb = 1 kg </li></ul><ul><li>1.06 qt = 1 liter </li></ul><ul><li>1 ml = 1 cc (JCAHO recommends using ml though) </li></ul>
11. 11. Conversion of units Fraction method <ul><li>Step 1 </li></ul><ul><ul><li>Put down starting value, with its units, as a fraction with 1 in denominator </li></ul></ul><ul><ul><li>i.e. How many kg in 150 lbs? </li></ul></ul><ul><ul><li>150 lbs </li></ul></ul><ul><ul><li>1 </li></ul></ul>
12. 12. <ul><li>Step 2 </li></ul><ul><ul><li>Place units you started with in the denominator and put units you want to convert to in numerator with corresponding equivalent values </li></ul></ul><ul><ul><li>150 lbs = 1 kg </li></ul></ul><ul><li>1 2.2 lbs </li></ul><ul><li>cancel out lbs; do math </li></ul><ul><li>150 = 68.2 kg </li></ul><ul><li>2.2 </li></ul>
13. 13. How many kg’s does a 180 lb male weigh? <ul><li>82 </li></ul><ul><li>360 </li></ul><ul><li>100 </li></ul><ul><li>60 </li></ul>
14. 14. Your patient is 5 ft 8 in. tall. Convert to cm’s <ul><li>34 </li></ul><ul><li>150 </li></ul><ul><li>80 </li></ul><ul><li>173 </li></ul>10
15. 15. Calculating doses from percentage-strength solutions <ul><li>A solution contains a solute, which is dissolved in a solvent. </li></ul><ul><li>The strength of a solution is expressed in percentage of solute to total solution. </li></ul><ul><ul><li>The % is the part of the active ingredient (solute) in a 100 mL of the preparation. </li></ul></ul><ul><li>We usually use a weight to volume type of preparation for respiratory drugs. </li></ul>
16. 16. <ul><li>A 20% saline solution contains 20 g of salt in enough water to make 100 ml of solution </li></ul><ul><li>A 5% albuteral solution contains 5 ml of albuteral in enough water to make 100 ml of solution </li></ul>
17. 17. Calculating with proportions (ratio/proportion method) <ul><li>1. </li></ul><ul><li>Set up a proportion </li></ul><ul><li>Original dose = desired dose </li></ul><ul><li> per amount per amount </li></ul>
18. 18. <ul><li>2. Convert to consistent units of measurements </li></ul><ul><ul><li>Don’t use g and mg at same time, make both g or both mg </li></ul></ul><ul><ul><li>Units on top should be the same </li></ul></ul><ul><ul><li>Units on bottom should be the same </li></ul></ul>
19. 19. How much salt is needed to make 1000 ml of a 20% soln? <ul><ul><ul><li>20 g = X g </li></ul></ul></ul><ul><ul><ul><li>100 ml 1000 ml </li></ul></ul></ul>
20. 20. Solve by cross-multiplying <ul><ul><ul><li>20 g = X g </li></ul></ul></ul><ul><ul><ul><li>100 ml 1000 ml </li></ul></ul></ul><ul><ul><ul><li>20g x 1000ml = 100ml X </li></ul></ul></ul><ul><ul><ul><li>20,000g/ml= 100ml X </li></ul></ul></ul><ul><ul><ul><li>20,000g/ml = 100ml X </li></ul></ul></ul><ul><ul><ul><li>100 ml 100ml </li></ul></ul></ul><ul><ul><ul><li>200g = X </li></ul></ul></ul>
21. 21. <ul><li>Flexeril comes as 5 mg per tablet. You have an order to give 2.5 mg. How many tablets will you need? </li></ul>
22. 22. <ul><li>This is how I think it through </li></ul><ul><li>What have I GOT? 5 mg/1 tab. </li></ul><ul><li>What do I want to GIVE? 2.5 mg </li></ul><ul><li>What do I GET? ???? </li></ul><ul><li>Set up proportion </li></ul><ul><li>5 mg = 2.5 mg </li></ul><ul><li>1 tab X (or ?) </li></ul>
23. 23. Now solve for unknown (you can make this an X or ?) <ul><li>5 mg = 2.5 mg </li></ul><ul><li>1 tab X tab </li></ul><ul><li>5 mg x X = 2.5 mg x 1 tab </li></ul><ul><li>X = 2.5 mg x 1 tab </li></ul><ul><li>5 mg </li></ul><ul><li>X = 0.5 mg/mg x 1 tab (mg/mg will cancel themselves out and leave you with just tab) </li></ul><ul><li>X = 0.5 tab or ½ tab </li></ul><ul><li>So I would go GET ½ tablet to GIVE 2.5 mg </li></ul>
24. 24. <ul><li>Set up ALL drug calculations like this and it is easy, just make sure same measurements are on top and same measurements are on bottom. </li></ul><ul><li>In above example, mg’s both on top and tab’s on bottom. </li></ul><ul><li>Doesn’t matter which is on top or bottom as long as the same. </li></ul>
25. 25. <ul><li>1 tab = ? </li></ul><ul><li>5 mg 2.5 mg would work also </li></ul><ul><li>1 tab x 2.5 mg = ? x 5 mg </li></ul><ul><li>1 tab x 2.5 mg = ? </li></ul><ul><li>5 mg </li></ul><ul><li>0.5 tab = ? </li></ul>
26. 26. Dimensional Analysis <ul><li>What have I GOT? 5 mg in 1 tablet </li></ul><ul><li>What do I want to GIVE? 2.5 mg </li></ul><ul><li>What do I GET? ???? </li></ul><ul><li>? = 2.5 mg x 1 tab </li></ul><ul><li> 5 mg </li></ul><ul><li>? = 2.5 mg x 1 tab </li></ul><ul><li> 5 mg </li></ul><ul><li>? = 0.5 mg tab </li></ul><ul><li> mg </li></ul><ul><li>? = 0.5 tab </li></ul>
27. 27. Ratio Solutions <ul><li>May see isoproterenol in a 1:200 solution </li></ul><ul><li>Means 1ml of isoproterenol per 200 ml of solution </li></ul><ul><li>Set up as 1 ml </li></ul><ul><li> 200 ml </li></ul>
28. 28. How many mls of 1:200 Proventil soln will you give with 2.5 mg Proventil? <ul><li>Given: 1:200 soln. = </li></ul><ul><ul><li>1 g of Proventil </li></ul></ul><ul><ul><li>200 ml of soln. </li></ul></ul>
29. 29. <ul><li>1 g Proventil = 2.5 mg Proventil </li></ul><ul><li>200 ml soln. X ml soln. </li></ul><ul><li>Convert g to mg </li></ul><ul><li>1000 mg = 2.5 mg </li></ul><ul><li>200 ml x ml </li></ul>
30. 30. <ul><li>1000 mg = 2.5 mg </li></ul><ul><li>200 ml x ml </li></ul><ul><li>1000mg x = 500 mg/ml </li></ul><ul><li>1000mg x = 500 mg/ml </li></ul><ul><li>1000 mg 1000 mg </li></ul><ul><li>x = 0.5 ml </li></ul>
31. 31. You have epi 1:100. How many mls for 30 mg? <ul><li>30 ml </li></ul><ul><li>15 ml </li></ul><ul><li>0.3 ml </li></ul><ul><li>3 ml </li></ul>10
32. 32. Calculations with a dosage schedule <ul><li>Sometimes the dose of a drug must be obtained from a schedule, which is usually based on the size of the patient. </li></ul><ul><li>Most common is weight but sometimes BSA (body surface area). (p42) </li></ul><ul><li>The body wt. must be obtained first, usually in kg then the dose can be calculated. </li></ul>
33. 33. <ul><li>The schedule for albuterol syrup in children 2 to 6 yrs old is 0.1 mg/kg of body wt. </li></ul><ul><li>You have a prepared-strength mixture of </li></ul><ul><li>2 mg/ 5ml; how much is needed for a 20 kg child? </li></ul><ul><li>1. Calculate the dose needed: </li></ul><ul><li>Dose = 0.1 mg x 20 kg = 2.0 mg </li></ul><ul><li> Kg </li></ul><ul><li>(kg’s cancel themselves out and just left with mg’s) </li></ul>
34. 34. 2. Calculate the amount of preparation needed <ul><li>Use ratio/proportion setup </li></ul><ul><li>2 mg x 2 mg (from calculation above) </li></ul><ul><li>5 ml X </li></ul><ul><li>2 mg (X) = 2 mg (5 ml) </li></ul><ul><li>2 mg (X) = 10 mg/mL </li></ul><ul><li>X = 10 mg/mL </li></ul><ul><li> 2 mg </li></ul><ul><li>X = 5 mL </li></ul>
35. 35. A dosage schedule for surfactant calls for 2.5 ml/kg birth weight. How much drug will you need for a 800 g baby? <ul><li>2 ml </li></ul><ul><li>0.2 ml </li></ul><ul><li>200 ml </li></ul><ul><li>20 ml </li></ul>10 Seconds Remaining