Dose Calculations

1. Dose Calculations 6 4

2. Systems of Measure • Three common systems still used today • Each deals with units of mass and volume • Metric • Apothecary • Household

3. Metric System • Most commonly used • Considered the most convenient since based on units of 10 • Basic units are • Meter Length • Liter Volume • Gram (Weight) Mass

4. Length 1 kilometer (km) = 1000 meters 1 hectometer = 100 meters 1 decameter = 10 meters Meter 1 decimeter = 1/10 meter 1 centimeter (cm)= 1/100 meter 1 millimeter (mm) = 1/1000 meter Metric System Volume • 1 kiloliter = 1000 liters • 1 hectoliter = 100 liters • 1 decaliter = 10 liters • Liter (L) • 1 deciliter = 1/10 liter • 1 centiliter = 1/100 liter • 1 milliliter (ml) = 1/1000 liter Weight • 1 kilogram (kg) = 1000 grams • 1 hectogram = 100 grams • 1 decagram = 10 grams • Gram • 1 decigram = 1/10 gram • 1 centigram = 1/100 gram • 1 milligram (mg) = 1/1000 gram 1 Gram = 1 ml = 1 cc 1 Kg = 1000 g = 2.2 lbs 1 mcg (μg) = one-millionth of a gram (0.000001 g)

5. Apothecary System • Old system of measurement • Considered to be less precise and convenient • Basic units are • Minim Volume • Grain (Weight) Mass • Written prescriptions place abbreviations before a roman numeral (gr V = 5 grains) • ¼ of a grain would be written as gr ¼ not 0.25 gr 1 Grain (gr) = 60 – 65 mg 1 dram = 60 gr 8 dr = 1 oz 16 oz = 1 lb

6. Household System • Approximate system of measurement • Basic units are • Weight ounces, pounds • Volume glass, cup, tablespoon, drop, quart, pint and gallon 1 t = 4 – 5 ml 1 T = 15 – 16 ml 1 pt = 500 ml 1 qt = 1000 ml = 2 pt 1 in = 2.54 cm

7. Dose calculations • As a paramedic you will have to calculate drug doses, infusion rates and strengths of drugs in the field. • Remember: • All units of measure must be converted to the same unit and system • The computed dose must be assessed to determine if it is reasonable • Use the same method of calculation every time

8. Weight Volume = 10 mg 1 ml = 10 mg/ml Concentrations • Refers to the strength of the drug (how many of one thing is present in something else) • 10 mg of drug in 1 ml of solution • Accomplished by dividing the weight of the drug by the volume of fluid it is in

9. Concentrations • Some drugs are labeled as a percentage • Refers to # of grams in 100 ml of solution • 1% Lidocaine 1 g of Lidocaine in 100 ml • 10% MgSO4 10 g of MgSO4 in 100 ml • D5W 5% Dextrose in water • 5 g of dextrose in 100 ml of Water • A 10 ml of 10% MgSO4 has 1 g of drug per 10 ml (or 100 mg/ml) 10% MgSO4 = 10 g MgSO4 100 ml = 10000 mg 100 ml = 100 mg/ml

10. Calculations • Three common types • Basic Formula (Most common) • Dimensional analysis • Ratios and proportions • May also see the ‘T’ method

11. Dimensional Analysis • Sets up all conversion factors in one equation and separated by ‘X’ • To solve calculation: • Set up the equation • Cancel pairs of units of numerator/denominator • Multiply the numerators • Multiply the denominators • Divide the numerator by the denominator

12. Dimensional Analysis • Example 1: • You are to administer fentanyl 50 mg IM. You have 75 mg of the drug in a 1 ml solution. How many ml will you give? 50 ml 75 2 ml 3 0.66 ml ml 1 ml 75 mg X 50 mg 1 = = = =

13. Dimensional Analysis • Example 2: • You are to administer 5 mg IV of valium. You have 10 mg of the drug in a 1 ml solution. How many ml will you give? 5 ml 10 1 ml 2 0.5 ml ml 1 ml 10 mg X 5 mg 1 = = = =

14. Ratio and Proportions • Compares two numbers and works like a fraction • Example: • Administer morphine 3 mg IV. You have 10 mg in 1 ml of solution. How many ml will you give? 10 mg : 1 ml :: 3 mg : x ml Means • Therefore 10x = 3 x = 3/10 x = 0.3 ml Extremes

15. Dose Want (D) Have (H) X Volume (V) = Basic Formula • D = “desired dose” = Want • H = “concentration of the drug” = Have • V = “volume the drug is supplied in” = Volume

16. Calculation #1 • The adult patient with nausea has no allergy to Dimenhydrinate. The appropriate dose is 20 mg. How many milliliters will be administered? • D = 20 mg • How is Gravol supplied? • 50 mg in a 5 ml vial • H = 50 mg • V = 5 ml

17. Calculation #1 Dose D H X V = • What is a side effect of Gravol? • Burning within the vein • How can it be diminished? • Dilute with saline prior to administration 5 ml 20 mg 50 mg X = 100 ml 50 = = 2 ml

18. Calculation #2 • An average size adult patient is actively seizing. The appropriate dose for diazepam is 2.5 mg to 5.0 mg IVP. • How is valium supplied? • 10 mg in 2 ml • Calculate the administration for the smallest dose

19. Calculation #2 Dose D H X V = 2 ml 2.5 mg 10 mg X = 5 ml 10 = 0.5 ml =

20. Calculation #3 • With the same patient, calculate the administration for the largest dose (5.0 mg)

21. Calculation #3 Dose D H X V = • Why can valium not be diluted with saline? • Is oil based • What would happen if it was diluted in saline? • Seizure Salad Dressing 2 ml 5 mg 10 mg X = 10 ml 10 = 1.0 ml =

22. Calculation #4 • A 28 y/o male has a fracture to the left tib/fib. His pain is 10/10. The appropriate dose for morphine sulfate is 2.5 – 5 mg. • How is morphine supplied? • 10 mg in 1.0 ml • Calculate the administration for the smallest dose

23. Calculation #4 Dose D H X V = 1 ml 2.5 mg 10 mg X = 2.5 ml 10 = 0.25 ml =

24. Calculation #5 • With the same patient, calculate the administration for the largest dose (5.0 mg)

25. Calculation #5 Dose D H X V = • How can an ACP administer morphine more accurately and safely? • Dilute 10 mg in 9 ml of saline in a 10 cc syringe • What is the concentration of the drug now? • 1 mg/ml 1 ml 5 mg 10 mg X = 5 ml 10 = 0.5 ml =

26. Calculation #5 Dose D H X V = • What are 3 potential side effects of morphine? • Nausea, hypotension, respiratory depression • How can we treat these effects? 1 ml 5 mg 10 mg X = 5 ml 10 = 0.5 ml =

27. Calculation #6 • A 70 y/o female is in extremis due to dyspnea preceded by two weeks of general malaise. She is lethargic, warm to the touch, diaphoretic, and has an Sa O2 of 80% on 100% O2. You decide to intubate. The appropriate dose for Versed is 2.0 – 5.0 mg. • How is Versed supplied? • 10 mg in 2 ml • Calculate the administration for the 2.0 mg dose

28. Calculation #6 Dose D H X V = 2 ml 2.0 mg 10 mg X = 4.0 ml 10 = 0.4 ml =

29. Calculation #7 • With the same patient, calculate the administration for the largest dose (5.0 mg)

30. Calculation #7 Dose D H X V = 2 ml 5 mg 10 mg X = 10 ml 10 = 1 ml =

31. Calculation #8 • A 70 y/o male is c/o dyspnea. He has a PHx of CHF and on exam has rales in all lungs fields. • He is on Furosemide 40 mg PO but has not had any in two days since his prescription ran out and has not been refilled. • What is the most appropriate method of determining how much lasix the patient should receive? • Contact OLMC • How is Lasix supplied? • 40 mg in 4 ml • Calculate the administration for the 40 mg dose

32. Calculation #8 Dose D H X V = 4 ml 40 mg 40 mg X = 160 ml 40 = 4 ml =

33. Calculation #9 • You are called for a 24 y/o female, third trimester, who presents with grand mal seizures. Her husband states she has been bedridden with HTN X 3 weeks and denies any other PHx, medications or drug use. • The protocol for seizures with eclampsia states 1 g of magnesium sulfate • How is MgSO4 supplied? • 5 g in 10 ml • Calculate the administration dose

34. Calculation #9 Dose D H X V = 10 ml 1 g 5 g X = 10 ml 5 = 2 ml =

35. Calculation #10 • The pt is a 49 y/o female who presents with dyspnea, tachycardia and pallor. • She is normotensive, has Sa O2 of 98% on RA and a regular, narrow complex tachycardia on the monitor with a rate of 178. • Protocol states that Adenosine is the appropriate medication with a starting dose of 6.0 mg. • How is Adenosine supplied? • 6 mg in 5 ml • Calculate the administration dose

36. Calculation #10 Dose D H X V = 5 ml 6 mg 6 mg X = 30 ml 6 = 5 ml =

37. Calculation #11 • Your pt is a 55 y/o male c/o weakness. O/E the pt is pale, diaphoretic and has a slow regular pulse at 40 with a BP of 90/60. The ECG shows a sinus bradycardia with no ectopics. • Atropine is indicated. The dose is 0.5 mg • How is Atropine supplied? • 1 mg in 10 ml • Calculate the administration dose

38. Calculation #11 Dose D H X V = 10 ml 0.5 mg 1.0 mg X = 5 ml 1 = 5 ml =

39. Calculation #12 • You are called to the home of an 18 y/o female who has been stung by a bee. She has a known allergy. She was unable to self administer her epi pen due to device malfunction. • Your standing orders are for 0.3 mg SQ of 1:1,000 solution. • How is Epinephrine 1:1,000 supplied? • 1 mg in 1 ml • Calculate the administration dose

40. Calculation #12 Dose D H X V = 1 ml 0.3 mg 1.0 mg X = 0.3 ml 1 = 0.3 ml =

41. Weight Specific Dosing • Some medications require a Dose based on the patients weight. (Typically in kilograms) • May be a bolus or an infusion • 1.5 mg/kg of Lidocaine bolus in an arrest protocol • 5 μg/kg/min of Dopamine • To calculate the dose multiply the dose in units (g, mg, μg) by the pt’s weight in kg.

42. Calculation #13 • The pt is a 60 y/o female who presents unresponsive falling a fall down a flight of stairs. She has snoring respirations, purposeful movements of her arms, and an obvious deformity to her left parietal region. You decide to sedate and intubate the pt. Following the administration of Versed, prior to intubating you are to administer Lidocaine. She weighs approximately 110 lbs. • How is Lidocaine supplied? • 100 mg in 5 ml • Calculate the administration dose

43. Calculation #13 • First convert the weight of this patient • Then calculate the desired dose Weight 110 lb 2.2 kg/lb 50 kg = = Desired Dose 50 kg X 1.5 mg/kg 75 mg = =

44. Calculation #13 Dose D H X V = 5 ml 75 mg 100 mg X = 375 ml 100 = 3.75 ml =

45. Calculation #14 • The pt is a 40 y/o, 220 lb male. He is 1 week post operative bowel surgery, released from hospital 3/7 ago, responsive but lethargic • His Sa O2 is 95% on RA, HR 124 Reg and Weak, BP 70/40. • Your interventions are 100% O2 and a 1 L bolus of NaCl and has not shown a hemodynamic change. The protocol states 5 μg/kg/min infusion of dopamine.

46. Calculation #14 • What do we need to know? • How is dopamine supplied? • 800 mg in 500 ml of D5W • Weight of pt in kg • How much dopamine is to be delivered per minute • Concentration of dopamine per gtt • How many gtts per minute (will do this next module) 220 lb 2.2 kg/lb Weight 100 kg = = Desired Dose 100 kg X 5 μg/kg/min 500 μg/min = = 800 mg 500 ml 1600 μg/ml Concentration 1. 6 mg/ml = = =

47. Practical Session • Using the ‘D’ Kit. Identify all the medications found within it and document the following: • Name • Concentration • Indications • Contraindications • Dosing parameters • Appropriate calculation of dose

48. To continue… • We will continue calculations next month during the IV session of the program.