Chapter11

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© 2010 The McGraw-Hill Companies, Inc. All rights reserved

Math and Dosage Calculations for Health Care Third Edition

Booth & Whaley

McGraw-Hill 11-1

Chapter 11: Special Populations

Edited by B. Holmes MSN/Ed, RN

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Learning Outcomes

11.1 Explain why dosages for special populations must be based on theindividual patient.

11.2 Identify factors that affect the absorption, distribution,biotransformation, and elimination of

drugs in special populations.

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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 11-3

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Learning Outcomes (cont.)

11.6 Describe volume and medication limitations for special populations.

11.7 Calculate infusion rates based upon body weight.

McGraw-Hill 11-4

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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.

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Introduction (cont.)

• Clarify all confusing drug orders

• Calculate with absolute accuracy

• Verify that dose is safe

• Seek assistance from your supervisor

McGraw-Hill 11-6

Do not take short cuts with medication calculations.

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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 11-7

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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

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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

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• Distribution– Process that moves the drug from the

bloodstream to other body compartments

– Target site – where the drug produces its desired effect

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• 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

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• Elimination– Process where the drug leaves the body– Main route – urine– Other ways

• Air that we exhale• Sweat• Feces• Breast milk• Other body secretions

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• 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

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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.

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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

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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.

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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

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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

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• Hearing loss– Do they understand instructions?– Have them repeat information back to you

• Difficulty reading small print– Labeling– Tablet colors

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• 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.

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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

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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 medicationsMcGraw-Hill 11-22

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Dosages Based on Body Weight

• Amount of medication

per

• Weight of the patient

per

• Unit of time

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Dosages Based on Body Weight

Rule 11-1Rule 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 11-24

dose desired kg or dose desired kg xkg

mcgx

kg

mg

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Dosages Based on Body Weight (cont.)

Rule 11-1Rule 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.

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Calculate the amount to administerto 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 11-26

Example Example

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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

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Example (cont.) Example (cont.)

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McGraw-Hill 11-28

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Pediatric InjectionsStage 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

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Ensuring Safe Dosages

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Ensuring Safe Dosages (cont.)

Rule 11-2Rule 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 11-31

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Error Alert !

McGraw-Hill 11-32

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Error Alert !

Weight 8 lb 6 oz

Convert 6 ounces to pounds using as the conversion

Therefore 8 lb 6 oz = 8.375 lbMcGraw-Hill 11-33

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Practice

Determine whether the following order is safe. If safe, calculate the amount to administer.

McGraw-Hill 11-34

Patient: Child who weighs 14.5 kgOrdered: Amoxil 75 mg PO q8hOn hand: Usual child dose 20-40 mg/kg day q8h

Answer Dosage doesn’t fall within recommended dosage range; contact the physician.

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Daily Maintenance Fluid Needs (DMFN)

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Daily Maintenance Fluid Needs (DMFN)(cont.)

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Daily Maintenance Fluid Needs (DMFN) (cont.)

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• Amount of maintenance fluid required varies by weight

• Replacement fluids– Based on patient’s condition

• Vomiting• Diarrhea• Fever

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Rule 11-6 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 11-39

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Rule 11-6Rule 11-6(cont.)

3. If the patient weighs over 20 kg, find

McGraw-Hill 11-40

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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 11-41

Examples Examples

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Rule 11-7Rule 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.

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• 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 11-43

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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 11-44

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Creatinine Clearance

McGraw-Hill 11-45

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Creatinine Clearance (cont.)

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• Diseases that can damage kidneys– Hypertension– Diabetes– Congestive heart failure

• Drugs that alter or change kidney function– Lasix– Aminoglycoside antibiotics

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McGraw-Hill 11-48

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McGraw-Hill 11-49

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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 11-50

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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 11-51

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Ideal and Actual Body Weight (cont.)

Rule 11-8 Rule 11-8 Determining safe dosages for geriatric patientsCheck 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 11-52

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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 8hOn 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 11-53

Example Example

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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 11-54

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PracticeMr. Adams weights 172 lb (at ideal body weight). He is 5 ft, 7 in

tall. CLCR 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 hMcGraw-Hill 11-55

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Polypharmacy

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Drug Interactions

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Drug Interactions (cont.)

Rule 11-9Rule 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 useMcGraw-Hill 11-58

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Rule 11-9 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.

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• Factors causing adverse drug reactions– Advanced age

– Small body size

– Multiple illnesses

– Multiple medications

– Living alone

– Malnutrition

McGraw-Hill 11-60

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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)McGraw-Hill 11-61

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Drugs to Avoid in Specific Diseases

Less Severe Risk Drugs

Benign prostatic hypertrophy

Narcotics

ConstipationAntihistamines, anti-Parkinson’s drugs, GI antispasmodics, antidepressants

Diabetes mellitus Steroids, beta blockers

GI diseases Aspirin, potassium supplements

Insomnia Decongestants, bronchodilators, some antidepressants

Seizures Antipsychotics

McGraw-Hill 11-62

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Apply Your Knowledge

True or FalseA 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 11-63

Answer False

Answer True

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What are three resources you can consult to see if the calculated dose is a safe dose to administer?

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Answer 1. Drug label2. Package insert3. Drug literature

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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 11-65

Answer Weight and BSA

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McGraw-Hill 11-66

Answer

Daily maintenance fluid needs (DMFN)

What is the amount of fluid the patient needs over a 24-hour period called?

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Which age-related change would indicate a need to consider a smaller needle length for an IM injection?a. thinner, more fragile skinb. loss of subcutaneous tissuec. decreased muscle massd. difficulty swallowing

McGraw-Hill 11-67

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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

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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.

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Answer True

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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 11-70

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End of Chapter 11

McGraw-Hill 11-71

Perfection consists not in doing extraordinary things, but in doing ordinary things extraordinarily well.

~Angelique Arnauld

Chapter11

Health & Medicine

Transcript of Chapter11