Tuesday, November 28, 2023

# When To Round In Nursing Math

## Body Surface Area Calculations Nursing Review

Medication Math – Decimals and Rounding

This review will discuss how to solve nursing dosage and calculations on body surface area!

Body surface area is used to help calculate the most accurate medication dosage for a patient. For example, some medications ordered for a pediatric patient may be based on body surface area and strong medications, such as chemo agents .

This review will demonstrate step-by-step how to calculate the following:

• Body surface area of a patient based on weight and height
• Calculating the childs dose based on the childs BSA and the normal adult dose
• Calculating the amount of medication you will administer based on the patients BSA and physicians order

Calculating BSA is based on the patients weight and height. It can be calculated using a nomogram or specific formulas, which is what this review will cover.

In addition, its important to know that body surface area is expressed in m2, square meter, which means that body surface is the amount of square meters of a persons body.

When solving these BSA problems you will need a calculator thatconfigures square roots of numbers, round per your programs guidelines, and memorize some formulas.

Therefore, before solving body surface area you need to commit to memory the following formulas below.

**The first two formulas will help you calculate the body surface area and you will select which formula to use based on if the scenario gave you the patients weight and height in the household or metric system.

## Front End Estimations With Addition

Example 1:

64 + 61

Front End Estimation:

Round off the 64 and the 61 leaving the front ends or the front, left most numbers, that is the 6 s, in place when the rounding off uses a number that is less than five, which the 4 and the 1 are. If, instead, the numbers were 67 and 69, for example, the 6 and 7 at the front end would be rounded up one number because both 7 and 9 are more than five.

64 + 61 can be approximated with 60 + 60 = 120

Precise Calculation:

64 + 61 = 125

As you can see, the front end estimation is very close to the precise mathematic calculation.

Example 2:

69 + 69 can be approximated with 70 + 70 = 140 and

The precise calculation is 138

Example 3:

64 + 64 can be approximated with 60 + 60 = 120 and

The precise calculation is 128

Example 4:

60 + 61 can be approximated with 60 + 60 = 120 and

The precise calculation is 121

## Calculating Basic Iv Drip Rates

Whoa, whoa, whoa. Look at you go, girlfriend!

You are just plowin on through this dosage calculation series and ready to rock that exam .

Today were talking about calculating intravenous drip rates.

There are two main reasons that it is super important for you know how to calculate drip rates accurately:

1. Many of the medications you will give in a hospital setting will be through the patients IV. 2. IVs are direct access to the bloodstream, so miscalculating a drip rate can cause dangerous issues very, very quickly.

Luckily for you, drip rates are where the dimensional analysis method really shines!

It makes it super easy to convert multiple units at one time and get to the correct answer quicker. If youre not convinced, check out this post.

Just a little reminder: Be confident!

As long as you follow the dosage calculation steps I laid out for you here, you will be good to go! Even though drip rates have multiple conversions, the same steps still apply. Youve got this!!

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## Measurement System Conversions To The Nearest Estimation Or Approximation

There are many occasions and situations where mathematics is not as precise as we often think it should. An example of this lack of precision is obvious when we consider our different measurements systems, including the household measurement system, the apothecary measurement system and the metric measurement system. There are few precise conversion factors from one measurement system to another most are approximations. These approximations, however, when accurate, are acceptable to use according to the standards of measurement.

Although measurement system equivalents are often shown with an = sign, they should be more accurately shown with the â sign which means about and approximately, rather than equal.

Examples of approximate system measurement conversions include:

1 fluid dram â 4 to 5 milliliters

1 teaspoon â 60 drops

1 kg â 2.2 pounds

## Mathematics Used In Nursing

In essence, math is a critical skill that RNs must master. Nurses have to use addition, ratios, fractions and algebraic equations at work to deliver medications and monitor patients. Math is necessary for calculating medication dosages, IV drip rates, drug titrations, and the patients’ caloric inputs and outputs. Besides that, some medications must be mixed or reconstituted before they can be administered, so the ratios for those must be calculated as well.

The Nest posts that solutions and medications are measured with different measurement systems, such as apothecary and metric there is no industry standard. Nurses must use their math skills to convert between systems as efficiently as possible. They also use the rules of decimals, fractions, number- rounding and Roman numerals, and memorize measurement abbreviations and conversion tables.

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## How Do You Perform Nursing Math

Math is performed with the use of a calculator when administering IV medications/fluids. The number of gtts per min is set on an IV pump through which the medication runs. When using syringes in addition to the IV fluid bag, you will have to manually do all that math with either a ruler or just by sight. There are tables for this purpose available online and it is important to be familiar with these however not necessary to memorize them as most RNs dont even know what they are called! These are used when administering drugs through a syringe.

## The Positions Of Numbers And Their Meanings: Decimal Places

As previously discussed, positional notations are used in whole numbers, decimal numbers and combination whole numbers with decimal places. Positional notations are used in whole numbers, decimal numbers and combination whole numbers with decimal places. These positional notations occur on both sides of a decimal point. The numbers to the left of the decimal point are whole numbers and the numbers on the right side of the decimal point are decimal numbers.

As you can see in the table above, the decimal number positions to the right of the decimal place, in the correct sequential order are:

• Tenths
• 6 is in the tenths place
• 7 is in the hundredths place

Number: 0.967

• 9 is in the tenths place
• 6 is in the hundredths place
• 7 is in the thousandths place

Number: 0.9672

• 9 is in the tenths place
• 6 is in the hundredths place
• 7 is in the thousandths place
• 2 is in the ten thousandths place

Number: 0.96728

• 9 is in the tenths place
• 6 is in the hundredths place
• 7 is in the thousandths place
• 2 is in the ten thousandths place
• 8 is in the hundred thousandths place

Number: 0.129672

• 1 is in the tenths place
• 2 is in the hundredths place
• 9 is in the thousandths place
• 6 is in the ten thousandths place
• 7 is in the hundred thousandths place
• 2 is in the millionth place

The number 45.7589 is 45 and 7589 ten thousandths.

• 3.44 = 3.4
• 987.5328 = 987.533

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## Want To Connect With Other Nurses

Our non-Facebook community is just what you need.

Lets say you need to give 500 ml IVPB Vancomycin over two hours.

500 / 2 hrs = 250 ml/hr

I want 500 mls to go in over two hours, so just divide by two and itll go in at 250/hr! If its going in over more than an hour, your rate will be less than your amount.

## Following Are Some Math Practice Questions That Nurses Can Practice

When to Round Decimals for Dosage Calculations | Nursing & NCLEX || FearlessRN

Here are 20 math practice questions for nurses.

1. The physician orders Wellcovorin 1mg IM. The drug comes in powdered form in a vial containing 50mg. The directions for reconstitution are: Add 5mL of diluent for a final concentration of 10mg/1mL. After reconstituting, how many mL should you draw up?

2. A patient is receiving an infusion of aminophylline. The IV solution contains 250mg of aminophylline in 250 ml of D5W, infusing at 15mL/hr. How many mg of aminophylline is the patient receiving per hour? Per-minute?

3. The recommended dose range for carmustine is 200-250mg/m /dose. What would be the appropriate dose range for a patient with a BSA of 0.83m?

4. A patient is to receive lidocaine 1mg/min IV. You have a solution of 2g Lidocaine in 1000mL D5W. How many mL/hr should the patient receive?

5. The physician orders IV Diprivan 100mcg/kg/min. Your patient weighs 165 lb. How many mcg/min should the patient receive?

6. Your patient is to receive dacarbazine 375mg/m /day IV. The patients height is 72 inches and his weight is 180 lbs. How many mg should your patient receive? .

7. The physician orders D5LR 1000mL/10hr. The IV set drop factor is 20gtt/mL. How many gtt/min should the patient receive?

8. Your patient is to receive an infusion of Pitocin. The drug comes 20U/1000mL in D5W. The doctor orders 0.01U/min. How many mL/hr should the patient receive?

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## Math Exam Tips For Nursing School

I hated nursing school math exams. Im not the best at math, at all. Ive never taken a calculus or physics class in my entire life. However, like many nursing schools, mine had a med math exam in every single course. You had to get a 90% or above or you failed the entire class, no matter what the rest of your grade was. And if that happened, you had to wait until the next year to retake the class.

No pressure.

In the real world, I use a few types of math but nothing like those darn tests. Ill calculate pump rates for IVPB meds and doses for partial dose meds. Thats about it. We always double check our math with a few other nurses prior to administration. Also, the computer typically calculates it as well. However, if you work with babies or in peds, youll be giving everything based on weight. So that means more math!

These are the different things youll need to know for those math exams and how to pass them.

## Why Does 5 Go Up

5 is in the middle … so we could go up or down. But we need a method that everyone agrees to.

So think about sport: we should have the same number of players on each team, right?

 0,1,2,3 and 4 are on team “down” 5,6,7,8 and 9 are on team “up”

And that is the “common” method of rounding. Read about other methods of rounding.

A farmer counted 87 cows in the field, but when he rounded them up he had 90.

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## Front End Estimations With Addition With Larger Numbers

Example 1:

604 + 716

Front End Estimation:

Round off the 604 and the 716 leaving the front ends that are the 6 and the 7 in place when the rounding off uses a number that is less than five.

604 + 716 can be approximated with 600 + 700 = 1300

Precise Calculation:

604 + 716 = 1, 320

As you can see, the front end estimation is very close to the precise mathematic calculation.

Example 2:

680 + 779 can be approximated with 700 + 800 = 1500 and

The precise calculation is 1459

Example 3:

891 + 234 can be approximated with 900 + 200 = 1100 and

The precise calculation is 1125

Example 4:

545 + 894 can be approximated with 500 + 900 = 1400 and

The precise calculation is 1439

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18. The physician orders Cytoxan 425mg IV for a patient weighing 154lb. The recommended dose range is 3-5mg/kg IV twice weekly. Is this an appropriate dose for this patient?

19. A patient is to receive Vibramycin 100mg PO twice a day for 7 days. On hand are 50 mg capsules. How many capsules will the patient receive for the 8 AM dose?

20. The physician orders Zantac 50mg IM every 6hours. The drug comes in a 6mL ampule labeled 25mg/mL. How many mL should the patient receive for the 6 AM dose?

The above-mentioned questions are a classic example of a type of math problem presented to nursing students in the clinical setting. These problems are done most commonly with IVs but can be applicable for other types of medications and fluids given via other routes such as oral, inhalation, rectal, etc. Lets move to some faqs.

## Why Is Math Needed In The Field Of Nursing

Nurses use math to calculate dosages of medicine and to convert between different systems, such as weight, temperature and length. Math is also useful to calculate IV drip rates and drug titration.

The use of fractions, decimals, ratios and algebraic equations is common in the nursing field. When drawing liquid medicine, calculating the exact dosage is essential before administering it to the patient. Nurses also calculate dosage amounts based on a patients weight. Measurements in the nursing field are based on the metric system. Conversion of these measurements requires sharp mathematical skills. Types of conversions include pounds into kilograms, Fahrenheit to Celsius, and inches to centimeters.

The majority of IV bags include instructions to give the patient a particular amount of IV fluid over a certain number of hours. Algebraic equations are used to calculate the amount of IV fluid the patient needs per hour to meet these requirements. IV administration without electric pumps requires nurses to calculate how many drops per hour the patient receives.

## Converting From One Measurement System To Another

You will have to convert from one measurement system to another when the doctor’s order, for example, orders a medication in terms of grains and you have the medication but it is measured in terms of milligrams . In this case, you will have to mathematically convert the gr into mg.

The table below shows conversion equivalents among the metric, apothecary and household measurement systems.

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## Calculating Intravenous Flow Rates Using Ratio And Proportion

The rule for intravenous flow rates is:

gtts/min = / x Drip or drop factor for the IV tubing

Doctor’s order: 0.9% NaCl solution at 50 mL per hour

How many gtts per minute should be administered if the tube delivers 20 gtt/mL?

X gtts per min = /60 = 1000/60 = 16.6 gtts which rounded off to the closest drop is 17 gtts

Rounded off to: 17 gtt/min

Here’s another example:

Doctor’s order: 500 mL of 5% D 0.45 normal saline solution to infuse over 2 hours

How many gtt per minute should be given if the tubing delivers 10 gtt/mL?

X gtts per min = /120 = 5000 / 120 = 41.66 gtts which is 42 gtts when it is rounded off

## Using Clinical Decision Making When Calculating Doses

TEAS Math Tutorial – Estimation and Rounding – Chapter 26

Nurses apply clinical decision making and professional thinking skills to the calculations of dosages and solution rates. There are times that nurses make an error in terms of their calculations and these error can be absolutely ridiculous and, at other times, these calculations can appear to be correct. Although there is no room for errors, a nurse should be able to immediately recognize that a calculation is wrong and incorrect. For example, if the nurse calculates an intravenous flow rate and the answer is that the rate of the flow should be 250 gtts per minute, the nurse should immediately recognize that this answer is ridiculous because it is not possible to accurately count this number of drops per minute. The nurse should recalculate the flow rate in this instance. If you are calculated the number of tablets that you should administer to the client according to the doctor’s order and your mathematics indicates that you should give 1/8th of a tablet or 12 tablets, for example, you should immediately know that your calculations are inaccurate because these answers are ridiculous.

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## The Front End Estimation Strategy

Although precise answers to algebraic, mathematical and arithmetic calculations is necessary, it is highly helpful to take an educated guess about the correct answer to a calculation particularly when the numerical values of the numbers are lengthy and complex.

For example, when you are asked to add or subtract very large and cumbersome numbers, it is highly helpful to take an educated guess about the correct answer to a calculation to avoid large and avoidable miscalculations and careless errors.

A highly useful estimation strategy called front end estimation. Front end estimation entails estimating the answer to an algebraic, mathematical or arithmetic calculation by simplifying numbers. When numbers are simplified and front end estimation is used, it will not give you the PRECISE answer to the calculation, but it will give you an approximate answer. You should, then, be able to compare your precise answer and calculation to the approximate answer that you got using front end estimation.

The front end estimation strategy involves the changing of numbers into zeros with the exception of those in the “front end” which are the beginning numbers starting on the left of the numbers. Below are examples of front end estimations and how these estimations compare to precise calculations.

## Performing The Calculations Needed For Medication Administration

Safe nursing care mandates accuracy in the calculation of dosages and solution rates. In this section you will get a brief review of basic arithmetic calculations and a review of the ratio and proportion method that is used for the calculation of dosages and solutions.

The three measurement systems that are used in pharmacology are the household measurement system, the metric system and the apothecary system.

The household measurement system is typically only used for patients who are in the home and not in a hospital or another healthcare facility. Measurements used in the household measurement system include teaspoons, tablespoons, drops, ounces, cups, pints, quart, gallons, and pounds:

UNIT OF MEASUREMENT
 1 kiloliter

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