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Chapter11 Chapter11 Presentation Transcript

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