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# Chapter11

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## Chapter11Presentation 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.)
• 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
• 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-
• 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
• 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-
• 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
• 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
• 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
• 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.
• 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
• 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?
• 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-
• 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-