Medical Math - Part 1 PDF

MEDICAL MATH PART 1  Review the Medical Math – Part 1 presentation posted on Brightspace. Complete the following Nearpod activities: Math Rules REQUIREMENTS Med Math - Practice Booklet 1 Optional: Complet...

MEDICAL MATH PART 1  Review the Medical Math – Part 1 presentation posted on Brightspace. Complete the following Nearpod activities: Math Rules REQUIREMENTS Med Math - Practice Booklet 1 Optional: Complete the weekly medical math practice booklets throughout the course (to be posted every Monday to Brightspace under the Medical Math folder).  Review metric and SI units, their prefixes, and documentation. Review unit conversion calculations. Review documentation rules related to fluid and drug administration. OBJECTIVES Estimate pediatric weight using different tools. Calculate drug doses and volumes. Calculate weight-based drug doses. Calculate infusion doses and administration rates over time. SI UNITS (SYSTÈME INTERNATIONAL D'UNITÉS) Internationally adopted system of Seven agreed-upon base units: measurement based on seven defining constants: The meter (m) The cesium hyperfine frequency Cs The kilogram (kg) The speed of light in vacuum c The ampere (A) The Planck constant h The second (s) The elementary charge e The Boltzmann constant k The Kelvin (K) The Avogadro constant NA The mole (mol) The luminous efficacy of a defined visible The candela (cd) radiation Kcd  Distance (m) THE METRIC Temperature (°C) SYSTEM Mass (g) Volume (L) METRIC SYSTEM PREFIXES Prefixes increase or decrease by a factor of 10 (10x bigger or small than the unit adjacent) where meter, gram, and liter are one. For example: 1 kilogram = 1000 grams 1 gram = 1000 milligrams 1 milligram = 1000 micrograms  Distance Meters = (feet x 0.3) + (inches x 0.025) COMMON Temperature MEDICAL CONVERSIONS Celsius = (°F - 32) x 5/9 Mass Kilograms = pounds ÷ 2.2 DOCUMENTATION OF UNITS Symbols: Use the standardized prefix symbol. Capital and lowercase letters may indicate different units so be careful to use them appropriately. (G = giga, g = gram) Spacing: There is a space between the number and the unit. (1 mg or 38 °C) Decimals: Decimals are used to separate whole from partial numbers. There is no decimal if the number is whole (4 mg not 4.0 mg). There is always a zero before the decimal for a partial number. (0.45 mL not.45 mL) Plurals: The unabbreviated unit is made plural if the value is greater than 1 except for temperature which is always made plural (0.2 meter, 4.5 grams, 0 degrees). Abbreviated units are never made plural ( 5 mL not 5 mL's). DOCUMENTATION OF UNITS Periods: Periods are not added to the symbol unless it's at the end of a sentence. Commas: Commas are not used for number separation. Spaces are used for number with five or more digits (1 234 567 not 1,234,567). Four-digit numbers are acceptable both with, and without, a space (1234 or 1 234). Hyphens: Hyphens are not required for a single modifier (5 liter bag vs 2-year-old boy). If a hyphen is used, the units should be written in full, not abbreviated (2-milliliter dose not 2-mL dose). PEDIATRIC WEIGHT CALCULATION There are many formulas and tools that estimate the weight of a pediatric patient. Age-base "Best Braslow tape APLS formula OBHG Guess" formula Gender and 1-10 years = 0-12 months 0-12 months height-based 2 x age + 4 = (age in = 4 + (age in weight >10 years = months +9) ÷ months/2) estimation 3 x age 2 1-9 years = (2 Accuracy Under- 1-5 years = 2 x age) + 10 decreases estimates x age + 10 10-14 years = above 25 kg weights in all 6-14 years = age x 3 age age x 4 categories Over- estimates weights in the 6-14 year age group FOR ALL PHARMACOLOGY TEST QUESTIONS OBHG 0-12 months = 4 + (age in months/2) 1-9 years = (2 x age) + 10 10-14 years = age x 3  MEDICATION ADMINISTRATION – NON-INJECTABLE Medication may be administered as pills, capsules, liquids, patches, or other non- injectable formulations. The formulation supplied by the pharmacy usually corresponds to the dose to be administered. Liquids should be drawn into a syringe for precise dose measurement. Pills and patches may be cut along score lines to administer half the total dose contained in the pill or patch.  MEDICATION ADMINISTRATION - INJECTABLE Injectable medications may come in ampoules or vials. Vials may contain a powdered form of the drug that must get reconstituted prior to administration. Vials may contain multiple doses of a drug. Ampoules are single-use only but may contain more drug than is prescribed. Only draw up the volume of drug to be administered. Drugs are drawn up using a syringe and blunt-tip needle. The blunt-tip needle is then exchanged for an injection needle for administration of the drug. MAKING AN INFUSION Some drugs are administered by an infusion over time which means they need to be in an IV bag for administration. Some drugs come pre-mixed. The IV bag is connected to an administration set and the infusion rate per hour is calculated. Some drugs must be added to a generic IV bag prior to connecting the IV set and calculating the infusion rate.  1 2 3 4 5 Determine Withdraw that Draw up your Add the drug Immediately the volume of volume of medication to the IV bag label your IV drug to be fluid from the from the vial through the bag with the removed from IV bag. or ampule drug injection name of the the vial or using a port. drug and the ampule. syringe. amount of drug added. MAKING AN INFUSION LABELING YOUR BAG OR SYRINGE 1. Write the drug name (generic name is preferred) 2. Write the amount of drug added to the syringe or bag. 3. Write the volume of fluid the drug was added to. 4. Write the unit concentration of the syringe or bag. 5. Consider writing the volume needed to give a dose. READING FLUID AND DRUG LABELS Commercial fluid and drug labels will display: The name of the drug or fluid. The total amount of fluid. The total amount of drug or solute in the fluid. The concentration of the preparation. READING DRUG AND FLUID LABELS INTERPRETING ORDERS You will receive orders to administer fluids or medications. Fluids are ordered in volume of fluid to be administered as a single dose or as an infusion over time. Administer an infusion of 0.9% NaCl at 100 mL/h. Administer a bolus of 250 mL of 0.9% NaCl. Fluid is documented in volume or volume/time. INTERPRETING ORDERS Medications are ordered as a single dose or as an infusion of a dose over time. Administer a bolus of 50 mcg of Fentanyl Administer an infusion of Fentanyl at 50 mcg/h. Medication is documented as dose or dose/time. CALCULATING DOSE TO BE ADMINISTERED Some orders are simple, and the dose is specified. Administer epinephrine 1 mg IV Some orders are for weight-based doses which will require you to calculate the dose from the patient's weight. Administer lidocaine 1.5 mg/kg IV For an 80 kg patient = 1.5 mg/kg x 80 kg = 120 mg IV CALCULATING WEIGHT-BASED DOSES Most pediatric medication and some adult medication is dosed based on the weight of the patient. Drugs can be dosed based on ideal body weight (IBW), lean body weight (LBW), or total body weight (TBW) depending on their pharmacokinetics. There are charts and formulas that help you determine IBW and LBW from a patient’s height. Your medical directive, standing order, or drug monograph will advise when you should use ideal or lean body weights. If not specified, use total body weight. CALCULATING WEIGHT-BASED DOSES - EXAMPLE You are ordered to administer midazolam 0.1 mg/kg IV. Your patient weighs 21 lbs. What dose of drug are you administering? 20 lbs ÷ 2.2 lbs/kg = 9.1 kg 0.1 mg/kg x 9.1 kg = 0.91 mg Therefore, you will administer 0.91 mg midazolam IV. ROUNDING DOSES OR VOLUMES Rounding doses or volumes to be administered is very common in medicine. Reasons may include: Medication formulary Ease of administration Simplified calculations It is important to make sure that if you are rounding a dose or volume, that you are not above or below the therapeutic dose for the patient. For this course, values >1 will be rounded to one decimal place and values