IV Infusion & Dilution Calculations
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Questions and Answers

In the intravenous infusion example, what is the prescribed volume of dextrose saline solution?

  • 160 mL
  • 1 L
  • 2 L (correct)
  • 100 mL

What is the flow rate set at for the intravenous infusion in the example?

  • 160 mL/h (correct)
  • 200 mL/h
  • 150 mL/h
  • 100 mL/h

In the intravenous infusion example, why is it necessary to convert liters to milliliters?

  • To decrease the volume
  • To confuse the calculation
  • To match the units used in the flow rate (correct)
  • To increase the volume

In the dilution example, what is the final volume of the morphine infusion required?

<p>30 mL (C)</p> Signup and view all the answers

What conversion factor is used to convert liters to milliliters?

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

What concentration of morphine is required after dilution?

<p>1 mg/mL (A)</p> Signup and view all the answers

How much morphine is contained in each stock ampoule?

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

In the first example, what is the initial volume used in the calculation?

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

What is the estimated final volume in the first example?

<p>150 mL (C)</p> Signup and view all the answers

How many stock ampoules are needed to obtain 30 mg of morphine?

<p>3 (D)</p> Signup and view all the answers

What is the total volume of solution from the morphine stock ampoules before dilution?

<p>3 mL (D)</p> Signup and view all the answers

What is the purpose of providing a "rough answer" estimate in the intravenous infusion problem?

<p>To provide a check on the final answer (D)</p> Signup and view all the answers

What formula is used in the intravenous infusion example to calculate time?

<p>$Time = Volume (mL) / Rate (mL/h)$ (D)</p> Signup and view all the answers

In the dilution example, what is being diluted with normal saline?

<p>Morphine (C)</p> Signup and view all the answers

How much normal saline is needed to dilute the morphine to the final volume?

<p>27 mL (C)</p> Signup and view all the answers

What calculation determines the amount of saline needed for dilution?

<p>Final volume - Volume of morphine (D)</p> Signup and view all the answers

What should be the initial step when solving drug calculations?

<p>Estimate a rough answer using common sense. (B)</p> Signup and view all the answers

Which of the following is a helpful strategy for solving drug calculation problems?

<p>Drawing a visual representation of the problem (A)</p> Signup and view all the answers

What does 'DPM' stand for concerning intravenous infusions?

<p>Drops Per Minute (C)</p> Signup and view all the answers

What should you do after calculating an exact answer to a drug calculation problem?

<p>Check if the final answer is close to the initial estimate. (C)</p> Signup and view all the answers

A patient requires a drug with a 'strength required' of 50mg. Which other value is needed to calculate the volume required?

<p>The stock strength (C)</p> Signup and view all the answers

Which formula is used to calculate the drip rate in drops per minute (DPM)?

<p>$DPM = \frac{VOLUME (mL) \times DROPS/mL}{TIME (h) \times 60}$ (A)</p> Signup and view all the answers

To calculate the time of infusion, which values are needed?

<p>Volume and rate (B)</p> Signup and view all the answers

What is the formula for calculating the volume (mL) of an intravenous infusion?

<p>$VOLUME (mL) = RATE (mL/h) \times TIME (h)$ (B)</p> Signup and view all the answers

What is the volume in mL if you have 1.5 L of fluid?

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

If a solution has a drip rate of 20 drops/mL, what fraction is used in the simplified drip rate calculation?

<p>1/3 (C)</p> Signup and view all the answers

What does 'dpm' stand for when calculating IV drip rates?

<p>Drops per minute (C)</p> Signup and view all the answers

What is the drip rate (DPM) if the volume is 1500 mL, the drops/mL is 20, and the time is 10 hours?

<p>50 dpm (C)</p> Signup and view all the answers

When administering tablets, what is the 'volume of stock' typically considered to be?

<p>1 (C)</p> Signup and view all the answers

What is the formula to determine the volume required when administering tablets?

<p>$(\text{Strength Required} \div \text{Stock Strength}) \times 1 $ (B)</p> Signup and view all the answers

If a doctor prescribes 750 mg of ciprofloxacin and you have 500 mg tablets, how many tablets should you administer?

<p>1.5 tablets (B)</p> Signup and view all the answers

In the tablet calculation formula, what does 'SS' stand for?

<p>Stock Strength (B)</p> Signup and view all the answers

If a patient requires 750mg of a drug and the stock strength is 500mg per tablet, how many tablets are needed?

<p>1.5 tablets (D)</p> Signup and view all the answers

What formula is used to calculate the total volume of fluid received by a patient intravenously?

<p>VOLUME (mL) = RATE (mL/h) x TIME (h) (A)</p> Signup and view all the answers

A patient receives an intravenous solution at a rate of 100 mL/h. How much fluid does the patient receive in 1.5 hours?

<p>150 mL (C)</p> Signup and view all the answers

If a patient is receiving 50 mL/h of a solution for 3 hours, what is the total volume of fluid the patient will receive?

<p>150 mL (C)</p> Signup and view all the answers

If a tablet contains 500mg of a drug, what fraction of the tablet provides 250mg of the drug?

<p>One-half (B)</p> Signup and view all the answers

A patient is prescribed a solution to be administered at 75 mL/h over a period of 2 hours. What is the total volume of solution administered?

<p>150 mL (D)</p> Signup and view all the answers

What does 'mL/h' represent in the context of intravenous infusions?

<p>The infusion rate (D)</p> Signup and view all the answers

If a patient needs 1000mg of a drug and each tablet contains 500mg, how many tablets should be administered?

<p>2 (B)</p> Signup and view all the answers

If a medication's stock strength is 10g in 200mL, what is the equivalent stock strength in mg?

<p>10,000 mg (A)</p> Signup and view all the answers

What does DPM stand for in the context of IV infusion calculations?

<p>Drops Per Minute (D)</p> Signup and view all the answers

What is the first step in calculating the volume required for a medication?

<p>Convert all values to the same units. (A)</p> Signup and view all the answers

A teenager needs 1.5 L of rehydration fluid over 10 hours. How many mL is 1.5L?

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

What formula is used to calculate the drip rate (DPM) for an intravenous infusion?

<p>Volume (mL) x Drops/mL / Time (h) x 60 (B)</p> Signup and view all the answers

If the strength required of a medication is 70mg and the stock strength is 10,000mg in 200mL, what is the volume required?

<p>1.4 mL (D)</p> Signup and view all the answers

What is the purpose of converting grams (g) to milligrams (mg) in medication calculations?

<p>To ensure the calculation is correct due to the units being the same (A)</p> Signup and view all the answers

If a giving set delivers 20 drops/mL, what information does this provide?

<p>The number of drops equivalent to one milliliter of fluid (C)</p> Signup and view all the answers

Flashcards

Drug calculation first step

Estimate a rough answer before calculating precisely.

Drawing a picture

Visually represent the problem to better understand the relationships between variables and make the problem easier to solve.

Volume Required Formula

A formula to calculate the volume required for oral or injected drugs.

The Volume Required Formula

VOLUME REQUIRED = (STRENGTH REQUIRED / STOCK STRENGTH) x VOLUME OF STOCK

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Drip Rate Formula

Drip Rate (DPM) = (VOLUME (mL) x DROPS/mL) / (TIME (h) x 60)

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Volume Formula

VOLUME (mL) = RATE (mL/h) x TIME (h)

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Rate Formula

RATE = VOLUME (mL) / TIME (h)

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Time Formula

TIME = VOLUME (mL) / RATE (mL/h)

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Strength Required

The amount of medication needed by the patient.

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Stock Strength

The concentration of medication available in the current stock.

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g to mg conversion

Converting grams (g) to milligrams (mg) involves multiplying by 1000.

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mg to g conversion

To convert milligrams (mg) to grams (g), divide by 1000.

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Volume Calculation Formula

VOLUME REQUIRED = (Strength Required / Stock Strength) x Volume

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Drops/mL

Number of drops delivered per mL of fluid.

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Drip Rate (DPM)

The rate at which fluid is administrated, measured in drops per minute.

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Calculating Tablets

If the ordered dose is 750mg and tablets are 500mg, you need 1.5 tablets.

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Volume of Fluid Formula

Calculates the total fluid received during an intravenous infusion over a period of time.

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Volume (mL) Calculation

The rate of infusion (mL/h) multiplied by the time (h).

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Given Values

Rate is 100 mL/h, Time is 1.5h.

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Estimation

If a patient receives 100 mL/hr, in 1.5 hours they receive 150 mL.

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Intravenous Infusion Calculation

With a rate of 100 mL/h over 1.5 hours, the patient receives 150 mL.

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IV Infusion Example

To solve: 100mL/hour multiplied by 1.5 hours equals 150mL.

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What is Drip Rate (DPM)?

Drip rate is measured in drops per minute, abbreviated as dpm.

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How to convert L to mL?

Multiply Liters (L) by 1000 to get milliliters (mL).

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What is the Drip Rate formula?

Volume (mL) / Time (hours) * Drops/mL / 60

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What is the Dosage Calculation formula?

Strength Required (SR) / Stock Strength (SS) * Volume of Stock

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What is 'Strength Required' (SR)?

The amount of medication needed for the prescribed dose.

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What is 'Stock Strength' (SS)?

The concentration of medication in the available tablets or solution.

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What is 'Volume of Stock' for tablets?

For tablets, the 'volume of stock' is always 1 because tablets aren't a solution.

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Why is estimating a good way to answer?

Estimating the answer helps verify if the calculated dose seems logical.

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Volume Calculation Example

Volume (mL) = 100mL x 1.5 = 150mL

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Infusion Time Formula

To determine infusion time: Time = Volume (mL) / Rate (mL/h)

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Intravenous Infusion Scenario Values

Key figures: Volume = 2 L, Rate = 160mL/h

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2 L in mL

Convert 2 L to mL: 2 L x 1000 = 2000 mL

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Liters to Milliliters

Converting Liters to Milliliters

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Calculating Infusion Time

Determining the answer.

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Volume Units

A milliliter is a smaller unit than a liter.

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What is Dilution?

To weaken the concentration of a solution by adding a solvent.

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Morphine Infusion Goal

Morphine infusion preparation to a final volume of 30 mLs, containing 30mg morphine.

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Morphine Concentration

Ampoules containing 10 mg of morphine per mL.

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Ampoules Needed?

3 ampoules needed to get 30 mg of morphine (3 x 10 = 30).

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Volume of Morphine

The 3 ampoules contain a total of 3 mL of solution (1 mL + 1 mL + 1 mL = 3 mL).

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Saline Volume?

Add 27mL of normal saline to the syringe.

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Final Volume

Final mixture of 30mg morphine in 30mL solution.

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Study Notes

  • To solve drug calculations, identify the type of calculation needed.
  • Estimate a rough answer as a first step, possibly with a visual aid.

Tablet/Oral Drug Calculation Formula

  • An easy way to remember this formula is SUNRISE (SR) / SUNSET (SS)
  • The formula to find out how many tablets to take (or for a drug taken orally or injected) is:
  • Volume required = (Strength required / Stock strength) x Volume of stock

IV Infusion Calculation Formula

  • The formula to determine drops per minute (DPM) for an intravenous infusion is:
  • Drip rate (DPM) = (Volume (mL) x Drops/mL) / (Time (h) x 60)
  • DPM stands for drops per minute

Intravenous Infusion Calculations (Volume/Rate/Time)

  • For IV infusions, these formulas help calculate volume, time or rate.
  • Volume (mL) = Rate (mL/h) x Time (h)
  • Rate = Volume (mL) / Time (h)
  • Time = Volume (mL) / Rate (mL/h)

Post-Calculation Check

  • After using the formula or calculating an answer, check if the answer is close to the initial estimate.

Example 1: Drug Made from Stock Solution

  • An example looks at finding the mLs to inject when the drug comes from a stock solution.
  • Question: Find the volume required, if a patient is ordered 70mg of pethidine, and the stock solution has 10g of pethidine per 200mL.
  • Need to use the formula: Volume Required = (Strength Required / Stock Strength) x Volume of Stock/1
  • Strength Required is 70mg, Stock Strength is 10g in 200mL
  • A rough answer to expect is more than 1mL, but less than 200mL
  • Convert 10g to mg to match units: 10g = 10,000mg
  • Substitute values: Volume Required = (70 / 10000) x 200/1 = 1.4mL
  • Final answer: 1.4mL

Example 2: Intravenous Infusion

  • An example illustrates how to calculate how many mLs to give over a time period, and how many drops per minute a patient receives.
  • Question: A teenager needs 1.5L of rehydration fluid over 10 hours via IV, with a giving set of 20 drops/mL. Calculate the drip rate.
  • Use the formula Drip Rate (DPM) = (Volume (mL) x Drops/mL) / (Time (h) x 60)
  • Volume is 1.5L, Drops/mL is 20, and Time is 10 hours.
  • Since drops per mL is 20, there are 60 minutes in an hour, fluid per hour x (20/60) = 1/3
  • Therefore, one third of mL per hour (150 mL) should be the answer i.e. 50 mL (rough estimate).
  • Convert 1.5L to mL: 1.5L = 1500mL
  • Substitute values: Drip Rate (DPM) = (1500 x 20) / (10 x 60) = 50 dpm
  • Final answer: 50 dpm, which matches the initial estimate

Example 3: Tablets Taken Orally

  • This example shows how to calculate tablets for a certain dose.
  • Question: If 750mg of ciprofloxacin is prescribed and 500mg tablets are on hand, how many tablets should be given?
  • The formula to use is: Volume Required = (Strength Required / Stock Strength) x Volume of Stock
  • Strength Required is 750mg, Stock Strength is 500mg
  • Expect to need more than one tablet but less than two because tablets are 500mg each.
  • Volume of stock is 1.
  • Substitute values: Volume Required = (750 / 500) x 1 = 1.5 tablets
  • Final answer: 1.5 tablets

Example 4: Intravenous Infusion Amount

  • This example shows calculating fluid amount a patient receives.
  • Question: A patient receives 100mL/h of a solution for 1.5 hours. How much fluid do they receive?
  • Use the formula Volume (mL) = Rate (mL/h) x Time (h)
  • Rate is 100mL/h, Time is 1.5h
  • If the patient gets 100mL in an hour they would get half of that (50mL) in half an hour so expect 150mL
  • Substitute values: Volume (mL) = 100mL x 1.5 = 150mL
  • Final answer: 150mL (matches initial estimate)

Example 5: Intravenous Infusion Time

  • Another example of how to calculate how long an infusion will take.
  • Question: Find how long infusion will take, if a patient is prescribed 2L of dextrose saline solution, and the flow rate is set at 160mL/h.
  • Solve with formula Time = Volume (mL) / Rate (mL/h)
  • Volume is 2L, Rate is 160mL/h
  • Convert 2L to mL: 2L = 2000mL
  • Since 2L = 2000mL and the flow rate is 160mL per hour, roughly between 10 and 15 hours.
  • Substitute values: Time = 2000 / 160 = 12.5 hours

Example 6: Dilution

  • This example shows how to dilute a drug to the required concentration.
  • Question: Prepare a morphine infusion, get 30mg to a final volume of 30mL. Stock ampoules of morphine contain 10mg/mL. How much normal saline is needed?
  • Each stock ampoule has 10mg morphine, so 3 ampoules needed for 30mg
  • 3 stock ampoules is 3mL of solution (1mL each) i.e. 30mg morphine in 3mL solution from stock.
  • Because you need 30mg morphine in 30mL solution, add 27mL of saline to the syringe: 30 - 3 = 27.

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Drug Calculations PDF - Flinders University - Practice Questions

Description

Examples of calculating intravenous infusion rates and drug dilutions. Includes determining prescribed volumes, flow rates, and morphine concentrations after dilution. Provides step-by-step solutions for healthcare professionals.

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