Nursing Dosage Calculations Quiz
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Questions and Answers

What should the nurse calculate for the dosage?

40 mg

What is the quantity of the dose available?

100 mg

The nurse should administer ____ mL subcutaneously every 12 hr.

0.8

What is the nurse's final administered dosage per dose for cefixime?

<p>2 mL</p> Signup and view all the answers

Should the nurse convert the units of measurement for cefixime?

<p>No</p> Signup and view all the answers

What is the dose available for cefotaxime?

<p>1 g</p> Signup and view all the answers

What is the total infusion time for 500 mL?

<p>4 hr</p> Signup and view all the answers

What should be the IV flow rate if administering 100 mL over 45 minutes?

<p>133 mL/hr</p> Signup and view all the answers

The nurse should convert the units of measurement when infusing over 45 minutes.

<p>True</p> Signup and view all the answers

What is the nurse's calculated IV flow rate for delivering 100 mL over 45 min?

<p>133.33</p> Signup and view all the answers

What is the unit of measurement the nurse should calculate for solid dosage?

<p>capsules</p> Signup and view all the answers

What is the standard conversion for 1 mg?

<p>1,000 mcg</p> Signup and view all the answers

How should dosages greater than 1.0 be rounded?

<p>To the nearest tenth</p> Signup and view all the answers

1 g = ______ mg

<p>1,000</p> Signup and view all the answers

What is the correct dose to administer for 0.2 g when 100 mg is available per capsule?

<p>2 capsules</p> Signup and view all the answers

If the calculated dose is 0.746 mL, how should it be rounded?

<p>0.75 mL</p> Signup and view all the answers

Rounding down occurs when the number to the right is less than 5.

<p>True</p> Signup and view all the answers

What should the nurse do if a medication dosage is calculated as 0.743 mL?

<p>Round to 0.74 mL</p> Signup and view all the answers

Which method can be used for dosage calculation?

<p>All of the above</p> Signup and view all the answers

What is the equivalent of 0.25 g in mg?

<p>250 mg</p> Signup and view all the answers

What quantity should a nurse administer if the available dose is 10,000 units/mL and the required dose is 8,000 units?

<p>0.8 mL</p> Signup and view all the answers

What does 133.3333 round to?

<p>133</p> Signup and view all the answers

What is the unit of measurement the nurse should calculate when administering IV fluids?

<p>gtt/min</p> Signup and view all the answers

What is the volume the nurse should infuse for a specific IV medication?

<p>1,500 mL</p> Signup and view all the answers

What is the total infusion time for the IV medication?

<p>10 hr</p> Signup and view all the answers

Should the nurse convert the units of measurement when the unit is mL?

<p>False</p> Signup and view all the answers

How many drops per minute should be delivered if the prescription is for 1,500 mL over 10 hours?

<p>38 gtt/min</p> Signup and view all the answers

How many gtt/min should the nurse administer for 100 mL over 30 min?

<p>33 gtt/min</p> Signup and view all the answers

How many mL should the nurse administer per dose for amoxicillin 20 mg/kg/day to a 44 lb preschooler?

<p>mL depends on weight dosage calculation</p> Signup and view all the answers

How many tablets of haloperidol should the nurse administer for 2 mg every 12 hr?

<p>2 tablets</p> Signup and view all the answers

How many mL should the nurse administer for acetaminophen 650 mg at 500 mg/5 mL?

<p>6.5 mL</p> Signup and view all the answers

What is the drop factor for the manual IV tubing provided?

<p>10 gtt/mL</p> Signup and view all the answers

What flow rate (mL/hr) should be set for clindamycin 200 mg in 100 mL to infuse over 30 min?

<p>200 mL/hr</p> Signup and view all the answers

How much acetaminophen liquid should be administered for a 650 mg dose?

<p>6.5 mL</p> Signup and view all the answers

What is the volume the nurse should infuse?

<p>750 mL</p> Signup and view all the answers

What is the total infusion time?

<p>6 hr</p> Signup and view all the answers

What is the calculated IV flow rate in mL/hr?

<p>125 mL/hr</p> Signup and view all the answers

Should the nurse convert the units of measurement in this case?

<p>False</p> Signup and view all the answers

What is the rate at which vancomycin should be infused?

<p>22 gtt/min</p> Signup and view all the answers

What volume should the nurse infuse for vancomycin administration?

<p>100 mL</p> Signup and view all the answers

What is the total infusion time for vancomycin?

<p>30 min</p> Signup and view all the answers

The units of measurement for time must be converted when infusing medication.

<p>True</p> Signup and view all the answers

What is the calculated infusion rate for vancomycin in mL/hr?

<p>200 mL/hr</p> Signup and view all the answers

What is the dose the nurse should administer for the desired amount of medication?

<p>80 mg</p> Signup and view all the answers

What is the available dose of the medication?

<p>10 mg</p> Signup and view all the answers

What is the quantity of the dose available when it is 10 mg per 1 mL?

<p>1 mL</p> Signup and view all the answers

How much of the medication should be administered when 80 mg is desired?

<p>8 mL</p> Signup and view all the answers

What is the desired dose of haloperidol?

<p>2 mg</p> Signup and view all the answers

What is the available dose of haloperidol?

<p>1 mg</p> Signup and view all the answers

How many tablets should be administered for a prescription of 2 mg haloperidol?

<p>2 tablets</p> Signup and view all the answers

What is the client's weight in pounds for the dosage calculation?

<p>44 lb</p> Signup and view all the answers

What is the equivalent weight in kilograms for the client who weighs 44 lb?

<p>20 kg</p> Signup and view all the answers

What is the calculation that converts pounds to kilograms?

<p>44 lb × (1 kg/2.2 lb)</p> Signup and view all the answers

What is the total volume in mL for a dose that is administered as 4 mL?

<p>4 mL</p> Signup and view all the answers

What should the nurse calculate in milligrams?

<p>400 mg/day</p> Signup and view all the answers

What is the unit of measurement the nurse should calculate for the dose to administer?

<p>mL</p> Signup and view all the answers

What is the dose the nurse should administer for the patient's prescription?

<p>200 mg</p> Signup and view all the answers

What is the quantity of the dose available?

<p>5 mL</p> Signup and view all the answers

How much dose should the nurse administer if the desired dose is 15,000 units and the available dose is 20,000 units?

<p>0.75 mL</p> Signup and view all the answers

The prescribed medication contains ____ units/mL.

<p>20,000</p> Signup and view all the answers

The nurse should administer ____ mL every 12 hours.

<p>0.8</p> Signup and view all the answers

What is the correct calculation setup for the dose required?

<p>Desired × Quantity / Have</p> Signup and view all the answers

The nurse should convert the units of measurement for every calculation.

<p>False</p> Signup and view all the answers

Calculate the number of mL the nurse should give if the desired dose is 650 mg and the available dose is 500 mg.

<p>6.5 mL</p> Signup and view all the answers

Study Notes

Dosage Calculation

  • Nurses are responsible for administering the correct amount of medication by calculating the precise amount to give.
  • Nurses can use three different methods for dosage calculation: ratio and proportion, formula (desired over have), and dimensional analysis.

Types of Calculations

  • Solid oral medication
  • Liquid oral medication
  • Injectable medication
  • IV infusion rates

Standard Conversion Factors

  • 1 mg = 1,000 mcg
  • 1 g = 1,000 mg
  • 1 kg = 1,000 g
  • 1 oz = 30 mL
  • 1 L = 1,000mL
  • 1 tsp = 5 mL
  • 1 tbsp = 15 mL
  • 1 tbsp = 3 tsp
  • 1 kg = 2.2 lb
  • 1 gr = 60 mg

General Rounding Guidelines

  • Rounding Up: If the number to the right is equal to or greater than 5, round up by adding 1 to the number on the left.
  • Rounding Down: If the number to the right is less than 5, round down by dropping the number, leaving the number to the left as is.

Solid Dosage Example

  • Problem: A nurse is preparing to administer phenytoin 0.2 g PO every 8 hr. The amount available is phenytoin 100 mg/capsule. How many capsules should the nurse administer per dose?
  • Solution
    • The nurse should administer 2 capsules of phenytoin.
    • The conversion factor is 1 g = 1,000 mg.
    • Therefore, 0.2 g is equivalent to 200 mg.
    • To administer 200 mg, the nurse will need to administer 2 capsules, because there are 100 mg per capsule.

Liquid Dosage Example

  • Problem: A nurse is preparing to administer amoxicillin 0.25 g PO every 8 hr. The amount available is amoxicillin oral suspension 250 mg/5 mL. How many mL should the nurse administer per dose?
  • Solution
    • The nurse should administer 5 mL of amoxicillin oral suspension.
    • The conversion factor is 1 g = 1,000 mg.
    • Therefore, 0.25 g is equivalent to 250 mg.
    • Since the available dose is 250 mg/5 mL, the nurse should administer 5 mL.

Injectable Dosage Example

  • Problem: A nurse is preparing to administer heparin 8,000 units subcutaneously every 12 hr. Available is heparin injection 10,000 units/mL. How many mL should the nurse administer per dose?
  • Solution
    • The nurse should administer 0.8 mL of heparin injection.
    • The dosage is 8,000 units and the available dose is 10,000 units/mL.
    • Therefore, 8,000 units is equivalent to 0.8 mL (8,000/10,000).

Using Ratio and Proportion

  • Ratio and proportion is a mathematical method used to solve problems involving ratios.
    • The nurse sets up a proportion that has two ratios: the dose to be administered and the dose available.
    • The nurse then solves for the unknown variable (X) using cross-multiplication.

Using Desired Over Have

  • Desired over Have is a formula used to calculate dosage.
    • The nurse divides the desired dose by the dose available and then multiplies the result by the quantity of the dose available.

Using Dimensional Analysis

  • Dimensional analysis is a method used to solve problems involving units of measurement.

    • The nurse sets up an equation that includes all the relevant units of measurement.
    • The nurse then multiplies and divides the ratios to cancel out unwanted units, leaving the desired unit of measurement.### Dosage Calculations

  • Dosage by weight: The nurse must calculate the correct dosage of medication based on the client's weight, the desired dosage, and the available dosage.

  • Step 1: Determine the unit of measurement the nurse should calculate.

  • If the client's weight is in pounds (lb), it must be converted to kilograms (kg).

  • If the desired dosage is in milligrams per kilogram per day (mg/kg/day), the nurse should calculate the total milligrams of medication required per day.

  • Step 2: Set up the formula: (Weight in lb * kg/lb) or (Desired dose * client's weight).

  • Step 3: Determine the unit of measurement needed for the final answer and the unit of the desired dose.

  • Step 4: Set up an equation and solve for X.

  • Step 5: If the dosage needs to be divided over a specific time period, divide the total dose by the number of doses.

  • Step 6: Determine the dose the nurse should administer, making sure it makes sense based on the available dose and the desired dose.

IV Infusion Rates

  • Electronic Infusion Pumps:
    • Deliver a specific amount of fluid over a specific period of time (e.g., 150 mL/hr or 50 mL/20 minutes).
  • Manual IV Tubing:
    • IV flow rates are calculated using the drop factor on the tubing (gtt/mL).
    • The drop factor is the number of drops per milliliter of solution.
    • The nurse counts the number of drops falling into the drip chamber over a minute to calculate the flow rate in drops per minute (gtt/min).
  • Using Dimensional Analysis:
  • Start with the unit of measurement you're aiming to calculate on the left side of the equation.
  • Then, write the ratios that contain the same unit on the right, ensuring the unit in the numerator matches the desired unit.
  • Continue adding ratios and conversion factors to cancel out unwanted units.
  • Using Desired over Have:
  • Determine the unit of measurement to be calculated.
  • Identify the volume to be infused and the total infusion time.
  • If necessary, convert time units.
  • Set up the equation with desired volume over time and solve for X.
  • Round to the nearest whole number, and check the flow rate makes sense for the prescribed infusion.

Summary

  • Dosage Calculation: Essential for nurses to ensure medication is administered safely and effectively.
  • Dosage by weight: Crucial in pediatrics and geriatrics to avoid over-dosing or under-dosing.
  • IV Flow Rates: Ensure precise fluid delivery for client needs.
  • Electronic Infusion Pumps: Offer accuracy and safety.
  • Manual IV Tubing: Requires careful calculation using the drop factor.

Calculating IV Flow Rates

  • There are two methods for calculating IV flow rates: Ratio and Proportion OR Dimensional Analysis
  • Ratio and Proportion method uses the formula: Volume (mL) x drop factor (gtt/mL) / Time (min)
  • Dimensional Analysis method uses units of measurement to set up an equation and solve for X.
  • To determine flow rate, first identify the unit of measurement needed (gtt/min or mL/hr).
  • Next, determine the total infusion time in minutes or hours, and the volume to be infused in milliliters (mL).
  • Conversion factors may be needed to make sure units of measurement cancel out.
  • It's crucial to double check if the flow rate is correct and makes sense based on the requested volume and infusion time.
  • Round up to the nearest whole number for gtt/min and mL/hr.
  • Leading zero is required for flow rates, to ensure accuracy.
  • Trailing zero is not used.
  • Examples:
    • Calculating IV flow rate with a drop factor of 10 gtt/mL
      • 100 mL to be infused over 45 min
      • IV flow rate = (100 mL x 10 gtt/mL)/45 min = 22.22 gtt/min rounds to 22 gtt/min
    • Calculating IV flow rate with an IV pump
      • 100 mL to be infused over 30 min
      • IV flow rate = 100 mL x (60 min/hr)/30 min = 200 mL/hr

Dosage Calculation Methods

  • Using Ratio and Proportion
    • Sets up a proportion between the dose available and the desired dose
    • Requires identifying the units of measurement and the quantity of the dose available
    • Solves for the unknown quantity using cross-multiplication
  • Using Desired Over Have
    • Calculates the desired dose divided by the dose available
    • Requires identifying the units of measurement and the quantity of the dose available
    • Multiplies the result by the quantity of the dose available
  • Using Dimensional Analysis
    • Sets up an equation with the unit of measurement being calculated on the left side
    • Identifies ratios containing the same unit of measurement
    • Places relevant ratios and conversion factors on the right side of the equation, ensuring units cancel out
    • Solves for the unknown quantity
  • Key Steps for Each Method
    • Identifying the desired dose and the dose available
    • Determining the units of measurement
    • Setting up the equation
    • Solving for the unknown quantity, including rounding if necessary
    • Determining if the calculated amount is logical and makes sense

Examples

  • Administering Furosemide (80 mg)
    • Dose available: 10 mg/1 mL
    • Calculated dose: 8 mL (using all three methods)
    • Administration: 8 mL PO (by mouth) daily
  • Administering Haloperidol (2 mg)
    • Dose available: 1 mg/tablet
    • Calculated dose: 2 tablets (using all three methods)
    • Administration: 2 tablets every 12 hours
  • Administering Amoxicillin Suspension (200 mg)
    • Dose available: 250 mg/5 mL
    • Calculated dose: 4 mL (using all three methods)
    • Administration: 4 mL PO every 12 hours
  • Administering Heparin (15,000 units)
    • Dose available: 20,000 units/1 mL
    • Calculated dose: 0.8 mL (using all three methods)
    • Administration: 0.8 mL by injection
  • Calculations for Clients with Varying Weights
    • The example provides calculations for administering a medication based on weight, adjusting the dose based on the client's weight in kilograms.
    • The calculation involves converting the client's weight from pounds to kilograms using the conversion factor 2.2 lb/1 kg.

Importance of Dosage Calculation

  • AccurateDosage calculation is crucial for safe medication administration
  • Improper dosage calculations can lead to serious adverse effects
  • Nurses are responsible for accurately calculating and administering medications
  • It's recommended to use multiple methods for dosage calculation to ensure accuracy and verify results.

Dosage Calculation Methods

  • There are three primary methods for calculating drug dosages: ratio and proportion, desired over have, and dimensional analysis.
  • All methods aim to determine the correct amount of medication to administer.
  • Ratio and proportion involves setting up a ratio of the desired dose to the available dose, then solving for the unknown quantity.
  • Desired over have similarly sets up a ratio of desired to available dose, but multiplies this ratio by the quantity of the available dose.
  • Dimensional analysis utilizes a series of ratios with units to cancel out unwanted units and arrive at the desired unit of measure for the calculation.
  • All methods use the following steps:
    • Identify the unit of measurement being calculated.
    • Identify the desired dose and available dose.
    • Determine if unit conversions are required.
    • Identify the quantity of the available dosage.
    • Set up the equation based on the chosen method.
    • Solve for the unknown variable.
    • Round the final answer as needed.
    • Review the answer to ensure it makes logical sense in the context of the medication and patient needs.

Examples

  • Example 1: Calculating Heparin Dosing

    • Desired: 15,000 units of heparin
    • Available: Heparin solution containing 20,000 units/mL
    • Calculation: X mL = (15,000 units/mL) * (1 mL/20,000 units) = 0.75 mL
    • Result: Administer 0.8 mL of heparin subcutaneously every 12 hours

  • Example 2: Calculating Acetaminophen Dosing

    • Desired: 650 mg of acetaminophen
    • Available: Acetaminophen liquid containing 500 mg/5 mL
    • Calculation: X mL = (650 mg/500 mg) * 5mL = 6.5 mL
    • Result: Administer 6.5 mL of acetaminophen liquid orally every 6 hours as needed for pain.

  • Example 3: Calculating IV Infusion Rate

    • Desired: Infuse 750 mL of D5W solution
    • Total Infusion Time: 6 hours
    • Calculation: X mL/hr = 750 mL / 6 hours = 125 mL/hr
    • Result: Set the IV pump to deliver D5W 750 mL IV at 125 mL/hr.

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Description

Test your knowledge of dosage calculations relevant to nursing practice. This quiz covers topics such as IV flow rates, unit conversions, and dosage rounding for medications like cefixime and cefotaxime. Perfect for nursing students and professionals looking to refresh their skills.

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