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  1. 1. Math and Dosage Calculations for Health Care Third Edition Booth & Whaley McGraw-Hill 11- Chapter 11: Special Populations Edited by B. Holmes MSN/Ed, RN
  2. 2. Learning Outcomes <ul><li>11.1 Explain why dosages for special populations must be based on the individual patient. </li></ul><ul><li>11.2 Identify factors that affect the absorption, distribution, biotransformation, and elimination of drugs in special populations. </li></ul>McGraw-Hill 11-
  3. 3. Learning Outcomes (cont.) <ul><li>11.3 Determine safe doses for special populations. </li></ul><ul><li>11.4 Calculate patient dosages based on body weight. </li></ul><ul><li>11.5 Find a patient’s body surface area (BSA). </li></ul>McGraw-Hill 11-
  4. 4. Learning Outcomes (cont.) <ul><li>11.6 Describe volume and medication limitations for special populations. </li></ul><ul><li>11.7 Calculate infusion rates based upon body weight. </li></ul>McGraw-Hill 11-
  5. 5. Introduction <ul><li>Two populations requiring extra consideration when calculating medication dosages </li></ul><ul><ul><li>Pediatric (less than 18 years old) </li></ul></ul><ul><ul><li>Geriatric (over 65 years old) </li></ul></ul><ul><li>Risk of harm is far greater due to the way they break down and absorb medications. </li></ul>McGraw-Hill 11-
  6. 6. Introduction (cont.) <ul><li>Clarify all confusing drug orders </li></ul><ul><li>Calculate with absolute accuracy </li></ul><ul><li>Verify that dose is safe </li></ul><ul><li>Seek assistance from your supervisor </li></ul>McGraw-Hill 11- Do not take short cuts with medication calculations.
  7. 7. Factors That Impact Dosing <ul><li>Standardized doses based on assumptions </li></ul><ul><ul><li>The patient’s body and age </li></ul></ul><ul><ul><li>Body systems are fully developed and functioning </li></ul></ul><ul><li>Assumptions do not hold true for all populations or situations </li></ul>McGraw-Hill 11-
  8. 8. Factors That Impact Dosing – PHARMACOKINETICS <ul><li>Study of how drugs are used by the body </li></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><li>Distribution </li></ul></ul><ul><ul><li>Biotransformation </li></ul></ul><ul><ul><li>Elimination </li></ul></ul><ul><li>Understanding these processes allows for adjustments for special populations </li></ul>McGraw-Hill 11-
  9. 9. Factors That Impact Dosing – PHARMACOKINETICS (cont.) <ul><li>Absorption </li></ul><ul><ul><li>Process that moves a drug from the site where it is given into the bloodstream </li></ul></ul><ul><ul><ul><li>IV medications bypass the absorption process </li></ul></ul></ul><ul><ul><ul><li>Oral medications – digestive system </li></ul></ul></ul><ul><ul><ul><li>Topical – through the skin </li></ul></ul></ul>McGraw-Hill 11-
  10. 10. Factors That Impact Dosing – PHARMACOKINETICS (cont.) <ul><li>Distribution </li></ul><ul><ul><li>Process that moves the drug from the bloodstream to other body compartments </li></ul></ul><ul><ul><li>Target site – where the drug produces its desired effect </li></ul></ul>McGraw-Hill 11-
  11. 11. Factors That Impact Dosing – PHARMACOKINETICS (cont.) <ul><li>Biotransformation </li></ul><ul><ul><li>Process that chemically changes the drug in the body </li></ul></ul><ul><ul><li>Occurs primarily in the liver </li></ul></ul><ul><ul><li>Helps to protect the body from foreign chemicals including drugs </li></ul></ul>McGraw-Hill 11-
  12. 12. Factors That Impact Dosing – PHARMACOKINETICS (cont.) <ul><li>Elimination </li></ul><ul><ul><li>Process where the drug leaves the body </li></ul></ul><ul><ul><li>Main route – urine </li></ul></ul><ul><ul><li>Other ways </li></ul></ul><ul><ul><ul><li>Air that we exhale </li></ul></ul></ul><ul><ul><ul><li>Sweat </li></ul></ul></ul><ul><ul><ul><li>Feces </li></ul></ul></ul><ul><ul><ul><li>Breast milk </li></ul></ul></ul><ul><ul><ul><li>Other body secretions </li></ul></ul></ul>McGraw-Hill 11-
  13. 13. Factors That Impact Dosing – PHARMACOKINETICS (cont.) <ul><li>Adjust dose </li></ul><ul><ul><li>If one of the four processes are not functioning within certain limits </li></ul></ul><ul><ul><li>Made according to nature and severity of patient’s condition </li></ul></ul><ul><ul><li>May by higher or lower than standard doses </li></ul></ul>McGraw-Hill 11-
  14. 14. Factors That Impact Dosing (cont.) <ul><li>Conditions that impact dosing </li></ul><ul><ul><li>Stomach or intestinal disorders </li></ul></ul><ul><ul><li>Liver disorders </li></ul></ul><ul><ul><li>Obesity </li></ul></ul><ul><ul><li>Kidney disease </li></ul></ul><ul><li>Functions of body systems change over the life of a person. </li></ul>McGraw-Hill 11-
  15. 15. Factors That Impact Dosing (cont.) <ul><li>Newborns – systems not fully developed </li></ul><ul><ul><li>pH of stomach is lower </li></ul></ul><ul><ul><li>Thinner skin </li></ul></ul><ul><ul><li>Liver still developing </li></ul></ul><ul><ul><li>Less circulation to muscles </li></ul></ul><ul><li>Geriatrics – systems deteriorate </li></ul><ul><ul><li>Skin and veins become fragile </li></ul></ul><ul><ul><li>Decreased liver function </li></ul></ul><ul><ul><li>Decreased kidney function </li></ul></ul><ul><ul><li>Poor circulation </li></ul></ul>McGraw-Hill 11-
  16. 16. Working with Special Populations <ul><li>Other Considerations </li></ul><ul><ul><li>Parent or caretaker may be administering or assisting with medications. </li></ul></ul><ul><ul><ul><li>Educate regarding medications </li></ul></ul></ul><ul><ul><li>Geriatric patients may have decreased awareness or understanding. </li></ul></ul>McGraw-Hill 11-
  17. 17. Working with Special Populations – GERIATRIC PATIENTS <ul><li>Show respect </li></ul><ul><li>Listen to their concerns </li></ul><ul><li>Encourage them to </li></ul><ul><ul><li>Use the same pharmacy to fill all prescriptions </li></ul></ul><ul><ul><li>Have one primary care physician to monitor and approve all medications </li></ul></ul><ul><ul><li>Keep a list of all medications </li></ul></ul>McGraw-Hill 11-
  18. 18. Special Populations – GERIATRIC PATIENTS (cont.) <ul><li>Decreased dexterity </li></ul><ul><ul><li>Injections </li></ul></ul><ul><ul><li>Eye drops </li></ul></ul><ul><ul><li>Open bottles </li></ul></ul><ul><li>Difficulty swallowing </li></ul><ul><ul><li>Drugs that cannot be crushed </li></ul></ul><ul><ul><li>Foods that can be mixed with drugs </li></ul></ul>McGraw-Hill 11-
  19. 19. Special Populations – GERIATRIC PATIENTS (cont.) <ul><li>Hearing loss </li></ul><ul><ul><li>Do they understand instructions? </li></ul></ul><ul><ul><li>Have them repeat information back to you </li></ul></ul><ul><li>Difficulty reading small print </li></ul><ul><ul><li>Labeling </li></ul></ul><ul><ul><li>Tablet colors </li></ul></ul>McGraw-Hill 11-
  20. 20. Special Populations – GERIATRIC PATIENTS (cont.) <ul><li>Short-term memory loss </li></ul><ul><ul><li>Written instructions </li></ul></ul><ul><ul><li>Medication calendars </li></ul></ul><ul><ul><li>Pill dispensers </li></ul></ul><ul><li>Avoid OTC or herbal meds until discussing with physician. </li></ul><ul><li>Do not take expired meds or borrowed meds. </li></ul>McGraw-Hill 11-
  21. 21. Teaching Patients About Medications <ul><li>1. Name of the medication </li></ul><ul><li>2. Purpose </li></ul><ul><li>3. How to store it </li></ul><ul><li>4. How long to take the medication </li></ul><ul><li>5. How and when to take it </li></ul><ul><li>6. How to know if it is effective </li></ul>McGraw-Hill 11-
  22. 22. Teaching Patients About Medications (cont.) <ul><li>7. Required follow-up tests, doctor appointments </li></ul><ul><li>8. Possible side effects and what to do </li></ul><ul><li>9. Interactions with other drugs and foods </li></ul><ul><li>10. Symptoms to report to the doctor </li></ul><ul><li>11. What to do if a dose is missed </li></ul><ul><li>12. Keeping a list of all medications </li></ul>McGraw-Hill 11-
  23. 23. Dosages Based on Body Weight <ul><li>Amount of medication </li></ul><ul><ul><ul><li>per </li></ul></ul></ul><ul><li>Weight of the patient </li></ul><ul><ul><ul><li>per </li></ul></ul></ul><ul><li>Unit of time </li></ul>McGraw-Hill 11-
  24. 24. Dosages Based on Body Weight <ul><li>Rule 11-1 Calculating dosage based on body weight: </li></ul><ul><li>1. Convert the patient’s weight to kilograms </li></ul><ul><li>2. Calculate the desired dose D by multiplying dose ordered by the weight in kilograms such as </li></ul>McGraw-Hill 11-
  25. 25. Dosages Based on Body Weight (cont.) <ul><li>Rule 11-1 (cont.) </li></ul><ul><li>3. Confirm whether or not the desired dose is safe by checking the label, package insert, or product literature. </li></ul><ul><li>4. Calculate the amount to administer, using fraction proportion, ratio proportion, dimensional analysis, or the formula method. </li></ul>McGraw-Hill 11-
  26. 26. Dosages Based on Body Weight (cont.) <ul><li>Calculate the amount to administer to a 3-year-old weighing 34 lb. </li></ul><ul><li>Ordered: hysocyamine sulfate 5 mcg/kg subq 1 h pre-anesthesia </li></ul><ul><li>On hand: hysocyamine sulfate 0.5 mg/mL </li></ul><ul><li>Convert 34 lb to kg = 15.5 kg </li></ul>McGraw-Hill 11- Example
  27. 27. Dosages Based on Body Weight (cont.) <ul><li>Find the desired dose: </li></ul><ul><li>77.5 mcg = D </li></ul><ul><li>Find the amount to administer: </li></ul><ul><li>77.5 mcg = 0.0775 = 0.08 mg </li></ul><ul><li>Amount to administer = </li></ul><ul><li>0.16 mL </li></ul>McGraw-Hill 11- Example (cont.)
  28. 28. Dosages Based on Body Weight (cont.) McGraw-Hill 11-
  29. 29. Pediatric Injections McGraw-Hill 11- Stage of Development Maximum Volumes for IM Injections Infant 0.5 – 1 mL Toddler, walking for at least 1 year 1 mL Preschooler/elementary school age 1 – 1.5 mL
  30. 30. Ensuring Safe Dosages McGraw-Hill 11-
  31. 31. Ensuring Safe Dosages (cont.) <ul><li>Rule 11-2 Ensuring Safe Dosages </li></ul><ul><li>When working with special populations, always check the package insert, drug label, or product literature to ensure the safety of the dose to be administered. </li></ul>McGraw-Hill 11-
  32. 32. Error Alert ! McGraw-Hill 11-
  33. 33. Error Alert ! <ul><li>Weight 8 lb 6 oz </li></ul><ul><li>Convert 6 ounces to pounds using as the conversion </li></ul><ul><li>Therefore 8 lb 6 oz = 8.375 lb </li></ul>McGraw-Hill 11-
  34. 34. Practice <ul><li>Determine whether the following order is safe. If safe, calculate the amount to administer. </li></ul>McGraw-Hill 11- Patient: Child who weighs 14.5 kg Ordered: Amoxil 75 mg PO q8h On hand: Usual child dose 20-40 mg/kg day q8h Answer Dosage doesn’t fall within recommended dosage range; contact the physician.
  35. 35. Daily Maintenance Fluid Needs (DMFN) McGraw-Hill 11-
  36. 36. Daily Maintenance Fluid Needs (DMFN) (cont.) McGraw-Hill 11-
  37. 37. Daily Maintenance Fluid Needs (DMFN) (cont.) McGraw-Hill 11-
  38. 38. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li>Amount of maintenance fluid required varies by weight </li></ul><ul><li>Replacement fluids </li></ul><ul><ul><li>Based on patient’s condition </li></ul></ul><ul><ul><ul><li>Vomiting </li></ul></ul></ul><ul><ul><ul><li>Diarrhea </li></ul></ul></ul><ul><ul><ul><li>Fever </li></ul></ul></ul>McGraw-Hill 11-
  39. 39. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li>Rule 11-6 To calculate daily maintenance fluid needs (DMFN) based on weight: </li></ul><ul><ul><li>1. If the patient weighs up to 10 kg, find </li></ul></ul><ul><ul><li>2. If the patient weighs 10 to 20 kg, find </li></ul></ul>McGraw-Hill 11-
  40. 40. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li>Rule 11-6 (cont.) </li></ul><ul><li>3. If the patient weighs over 20 kg, find </li></ul>McGraw-Hill 11-
  41. 41. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li> Find the DMFN for a patient weighing 16 kg. </li></ul><ul><li>DMFN mL = </li></ul><ul><li>DMFN mL = 1000 + 300 </li></ul><ul><li>DMFN mL = 1300 mL </li></ul><ul><li>Find the DMFN for a patient weighing 24 kg. </li></ul><ul><li>DMFN mL = </li></ul><ul><li>DMFN mL = 1500 + 80 </li></ul><ul><li>DMFN mL = 1580 mL </li></ul>McGraw-Hill 11- Examples
  42. 42. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li>Rule 11-7 </li></ul><ul><li>For pediatric patients and critically ill patients, the amount of solution in the IV tubing must be considered when determining infusion times and volumes. </li></ul>McGraw-Hill 11-
  43. 43. Daily Maintenance Fluid Needs (DMFN) (cont.) <ul><li>Standard IV tubing contains 10 mL of solution per five feet. </li></ul><ul><ul><li>When using a volume control chamber and standard tubing, medication will not reach patient until this 10 mL infuses. </li></ul></ul><ul><li>Low-volume tubing contains only 0.3 mL of solution per five feet. </li></ul>McGraw-Hill 11-
  44. 44. Practice <ul><li>Mrs. Robin had an oral intake of 750 mL. She weighs 145 lb How much more is required for the patient’s DMFN? </li></ul><ul><li>Convert wt to kg: 65.9 kg = 66 kg </li></ul><ul><li>DMFN = = 2420mL </li></ul><ul><li>2420 mL – 750 mL = 1670 mL </li></ul><ul><li>She requires 1670 mL to meet her DMFN. </li></ul>McGraw-Hill 11-
  45. 45. Creatinine Clearance McGraw-Hill 11-
  46. 46. Creatinine Clearance (cont.) McGraw-Hill 11-
  47. 47. Creatinine Clearance (cont.) <ul><li>Diseases that can damage kidneys </li></ul><ul><ul><li>Hypertension </li></ul></ul><ul><ul><li>Diabetes </li></ul></ul><ul><ul><li>Congestive heart failure </li></ul></ul><ul><li>Drugs that alter or change kidney function </li></ul><ul><ul><li>Lasix </li></ul></ul><ul><ul><li>Aminoglycoside antibiotics </li></ul></ul>McGraw-Hill 11-
  48. 48. Creatinine Clearance (cont.) McGraw-Hill 11-
  49. 49. Creatinine Clearance (cont.) McGraw-Hill 11-
  50. 50. Ideal and Actual Body Weight <ul><li>Geriatric patients – decreased proportion of lean body mass and water </li></ul><ul><ul><li>Alters distribution of drugs </li></ul></ul><ul><ul><li>Monitor serum drug levels </li></ul></ul><ul><li>Some water-soluble drugs strongly bound to lean tissue </li></ul><ul><li>Fat-soluble drugs distributed to body fat </li></ul><ul><ul><li>Slower release into circulation </li></ul></ul><ul><ul><li>Residual effects </li></ul></ul>McGraw-Hill 11-
  51. 51. Ideal and Actual Body Weight (cont.) <ul><li>Water soluble drug doses for </li></ul><ul><ul><li>Overweight patients – based on ideal body weight </li></ul></ul><ul><ul><li>Underweight patients (below ideal body weight) – based on actual weight </li></ul></ul>McGraw-Hill 11-
  52. 52. Ideal and Actual Body Weight (cont.) <ul><li>Rule 11-8 Determining safe dosages for geriatric patients </li></ul><ul><li>Check the package insert or product literature and check if dose ordered is safe based on renal function and ideal or actual patient weight. </li></ul><ul><li>If the dose is safe, calculate the amount to administer. </li></ul>McGraw-Hill 11-
  53. 53. Determine Safe Dosages for Geriatric Patients <ul><li>A 78-year-old male is 5’4” tall and weighs 180 lb. (Ideal weight range is 122–157 lb.) He has normal renal function and has a nonlife-threatening infection. </li></ul><ul><li>Ordered: Garamycin 85 mg IM q 8h </li></ul><ul><li>On hand: Garamycin injection, 40 mg/mL (usual dosage is 1 mg/kg) </li></ul><ul><li>Convert ideal body weight to kg: 55 to 71 kg </li></ul><ul><li>Safe dosage range = 55 mg to 71 mg </li></ul><ul><li>85 mg does not fall within this range. </li></ul><ul><li>Contact the physician. </li></ul>McGraw-Hill 11- Example
  54. 54. Error Alert! <ul><li>For medications that are strongly bound to lean body tissue, calculate an overweight patient’s dose on ideal body weight, not actual weight. </li></ul>McGraw-Hill 11-
  55. 55. Practice <ul><li>Mr. Adams weights 172 lb (at ideal body weight). He is 5 ft, 7 in tall. CL CR 60 mL/min </li></ul><ul><li>Ordered: Vancocin HCl 150 mg IV q6h </li></ul><ul><li>Daily recommended dosage for patients with normal renal function 2g in divided doses. Recommended daily dose for patients with creatinine clearance of 60 mL/min is 925 mg/24 h. </li></ul><ul><li>Is dose ordered safe? </li></ul><ul><li>Yes </li></ul><ul><li>600 mg/24 h, which is less than 925 mg/24 h </li></ul>McGraw-Hill 11-
  56. 56. Polypharmacy McGraw-Hill 11-
  57. 57. Drug Interactions McGraw-Hill 11-
  58. 58. Drug Interactions (cont.) <ul><li>Rule 11-9 To identify cases of polypharmacy and reduce the risk of drug interactions, ask elderly patients about: </li></ul><ul><ul><li>1. All medications they take which are prescribed by either their primary physician or specialists </li></ul></ul><ul><ul><li>2. Any over-the-counter medications they take </li></ul></ul><ul><ul><li>3. Any social drugs which they use </li></ul></ul>McGraw-Hill 11-
  59. 59. Drug Interactions (cont.) <ul><li>Rule 11-9 (cont.) </li></ul><ul><ul><li>4. Medications that they borrow from family and friends </li></ul></ul><ul><ul><li>5. Herbal and home remedies that they use </li></ul></ul><ul><ul><li>6. Bringing all medications they take to be checked. </li></ul></ul>McGraw-Hill 11-
  60. 60. Drug Interactions (cont.) <ul><li>Factors causing adverse drug reactions </li></ul><ul><ul><li>Advanced age </li></ul></ul><ul><ul><li>Small body size </li></ul></ul><ul><ul><li>Multiple illnesses </li></ul></ul><ul><ul><li>Multiple medications </li></ul></ul><ul><ul><li>Living alone </li></ul></ul><ul><ul><li>Malnutrition </li></ul></ul>McGraw-Hill 11-
  61. 61. Drug Interactions (cont.) McGraw-Hill 11- Drugs to Avoid in Specific Diseases Severe Risk Drugs Benign prostatic hypertrophy Antihistamines, anti-Parkinson’s drugs, GI antispasmodics, antidepressants Cardiac dysrhythmia Tricyclic antidepressants Clotting disorders Antiplatelet drugs, aspirin COPD Hypnotics, sedatives, beta blockers GI diseases NSAIDs, aspirin Seizures Metoclopramide (Reglan)
  62. 62. Drug Interactions (cont.) McGraw-Hill 11- Drugs to Avoid in Specific Diseases Less Severe Risk Drugs Benign prostatic hypertrophy Narcotics Constipation Antihistamines, anti-Parkinson’s drugs, GI antispasmodics, antidepressants Diabetes mellitus Steroids, beta blockers GI diseases Aspirin, potassium supplements Insomnia Decongestants, bronchodilators, some antidepressants Seizures Antipsychotics
  63. 63. Apply Your Knowledge <ul><li>True or False </li></ul><ul><li>A baby who weighs 6 lb 8 oz weighs 6.8 lb. </li></ul><ul><li>A baby who weighs 9.5 lb weighs 9 lb 8 oz. </li></ul>McGraw-Hill 11- Answer False Answer True
  64. 64. Apply Your Knowledge <ul><li>What are three resources you can consult to see if the calculated dose is a safe dose to administer? </li></ul>McGraw-Hill 11- Answer 1. Drug label 2. Package insert 3. Drug literature
  65. 65. Apply Your Knowledge <ul><li>Pediatric dosages should be rounded to the nearest: </li></ul><ul><li>a. Tenth </li></ul><ul><li>b. Hundredth </li></ul><ul><li>c. Thousandth </li></ul><ul><li>What two things are pediatric dosages often based on? </li></ul>McGraw-Hill 11- Answer Weight and BSA
  66. 66. Apply Your Knowledge McGraw-Hill 11- Answer Daily maintenance fluid needs (DMFN) What is the amount of fluid the patient needs over a 24-hour period called?
  67. 67. Apply Your Knowledge <ul><li>Which age-related change would indicate a need to consider a smaller needle length for an IM injection? </li></ul><ul><li>a. thinner, more fragile skin </li></ul><ul><li>b. loss of subcutaneous tissue </li></ul><ul><li>c. decreased muscle mass </li></ul><ul><li>d. difficulty swallowing </li></ul>McGraw-Hill 11-
  68. 68. Apply Your Knowledge <ul><li>The test used to measure the rate at which the kidneys filter the blood is called: </li></ul><ul><li>a. kidney function test creatinine </li></ul><ul><li>b. renal function test </li></ul><ul><li>c. creatinine </li></ul><ul><li>d. creatinine clearance </li></ul>McGraw-Hill 11-
  69. 69. Apply Your Knowledge <ul><li>True or False </li></ul><ul><li>For medications that are strongly bound to lean body tissue, calculate an overweight patient’s dose on the ideal weight, not actual weight. </li></ul>McGraw-Hill 11- Answer True
  70. 70. Apply Your Knowledge <ul><li>Polypharmacy occurs when a patient: </li></ul><ul><li>a. uses too many pharmacists </li></ul><ul><li>b. takes many medications at a time </li></ul><ul><li>c. borrows a medication from a friend </li></ul><ul><li>d. sees only one physician </li></ul>McGraw-Hill 11-
  71. 71. End of Chapter 11 McGraw-Hill 11- Perfection consists not in doing extraordinary things, but in doing ordinary things extraordinarily well. ~Angelique Arnauld