# Math For Nursing Majors (4 Ways Nurses Use Math)

If you’re considering a career in nursing, read on! Perhaps you think that once you graduate high school, you can leave the math behind. Not so! In practice, nurses use math every day. Keeping your math skills sharp and knowing statistics are essential to doing your job well.

There are several pathways to becoming a nurse. For our purposes, we’ll be focusing on the path that leads to a Bachelor of Science in Nursing Degree (BSN). Those that earn this degree generally take their NCLEX-RN (National Council Licensure Examination for Registered Nurses) in the few months following their graduation. By the way, there are several math questions on the exam!

So the question is, what kinds of math skills do you need to become an RN?

## 1. Dosage Calculations

One of the most important things that a nurse does is administer medication to patients. As you can imagine, it is really important that the nurse gets the doses correct or there could be serious consequences, possibly life threatening.

There are many people involved in a patient’s care – the doctor, the aides, technicians, physician’s assistants, and nurses. Generally though, when it’s time for a patient to take medicine, it’s the nurse who assists with that.

A dosage calculation is important because when nurses prepare medications for patients they are usually pulling from a general dose bottle that may not have the required dosage. A simple dosage calculation might look something like this:

### Example

Nurse Emily has a patient who needs 10 mg. of Medicine A twice per day. But, the pill only comes in 5 mg or 20 mg. What are Nurse Emily’s options?

Solution

Option 1: Split the 20 mg pills in half.

Option 2: Have the patient take two 5 mg. pills for each dose.

Okay, so that math is very basic. But, on the job, nurses will be performing these calculations regularly and for many patients.

Things can get more complicated if the patient’s weight needs to be taken into account. In addition to preparing doses of pills, nurses also administer medicine via an IV, as in the next example.

### Example

A doctor orders 20 units/kg/hr Heparin infusion to be started on a patient. The patient weighs 192 lbs. You are supplied with a bag of Heparin that reads 100 units/mL. How many mL/hr will you administer? (Source: registerednursern.com)

Solution

Immediately, we may notice that the doctor’s order is in units per kilogram per hour but the patient’s weight is in pounds. To accurately determine the mL/hr (milliliters per hour) that you must administer, we first convert pounds to kilograms. We should get a number that is smaller than 192 lbs since 1 kg = 2.205 lbs. Let the variable x represent the number of kilograms the patient weighs.

Set up a proportion, making sure the units match on both sides of the equation:

(1 kg/2.205 lbs)=(xkg/192 lbs)

Cross multiply:

192 = 2.205x

Divide both sides by 2.205:

x = 87.07

The patient weighs 87.07 kg – we’ll round down to 87 kg. The doctor wants 20 units/kg/hr to be administered. So, the patient needs (87)(20) = 1,740 units per hour. You’re supplied with a bag of Heparin that reads 100 units/mL which means that each milliliter is equal to 100 units. How many milliliters do you need? Let’s do another calculation – the variable y represents the number of milliliters needed:

(100 units/1 mL) = (1,740 units/y)

Cross multiply:

1,740 = 100y

Divide both sides by 100:

y = 17.4 mL

At this point, we have our answer! The patient needs 17.4 mL/hr of Heparin administered. (Note: Heparin is a drug that is used to prevent blood clots in patients.) ◾

A lot of the math that’s needed for a nurse falls into the category of statistics. Many BSN programs require nursing majors to take one semester of statistics.

## 2. Use statistics to assess a patient’s health

Nurses need to be comfortable with statistics like mean, median, mode, and standard deviation. They also need to work with percentiles. Nurses will often use these statistics to help identify patterns as well as learn more about the patient.

### Example

A nurse sees that a woman’s weight in a certain age group is in the 93rd percentile. The nurse knows this means that 93% of females of that age group weigh less than the patient. Already, the nurse knows a lot about the patient!

Assuming the patient has been to the practice before, the nurse can compare the woman’s weight percentile to her prior year percentiles. Is the patient gaining a lot of weight as she gets older? Has she always been heavier than her peers?

The nurse may then look at other descriptive statistics for the patient’s weight. Maybe the nurse will calculate the woman’s mean weight over the last ten visits. She may even calculate the standard deviation of the woman’s weight over that same time interval to notice any more trends.

(You can learn about other interesting uses of statistics here!)

## 3. Analyze data from patients

When a nurse is on a shift, he or she may need to observe reports and data on a patient. As part of that, the nurse may want to be alert to any trends in the data. This can help determine how best to care for the patient and it can provide valuable insight into what may be going on with the patient’s health.

The nurse needs to make decisions based on the patient’s data that can help her decide if the patient is getting better, if the patient needs a new treatment, or if the patient is remaining stable without any changes for better or worse. Statistics are all part of that process.

### Example

A 38 year old pregnant female who is 10 days overdue is being induced in the hospital. Nurses check on the patient and the baby and take vital signs, including monitoring the baby’s heartbeat.

The nurses record these findings. After 36 hours of labor, the nurse notices that the baby’s heartbeat has changed compared to the other readings.

While the heartbeat alone was not necessarily dangerous, compared to the other readings, it was a significant enough change that issued a red flag to the nurse. The nurse relays the information to the doctor who then decides to perform a Cesarean Section.

While the nurse likely didn’t whip out a TI-84 calculator to determine the standard deviation of the baby’s heart rate, she knew enough about statistics that the sudden change could indicate a risk. Having 36 hours of the baby’s heartbeat readings was sufficient data to notice the sudden change.

## 4. Interpret findings from clinical trials

Medical science is constantly advancing and nurses need to stay on top of the most recent findings; this includes being able to interpret the results from a clinical trial. In statistics classes, nurses learn how to conduct many types of statistical tests to help determine if a drug or treatment is effective.

There are many statistical tests nurses learn to apply including the one-sample t-test, the two-sample t-test, the paired samples t-test, the one-way ANOVA, and the two-way ANOVA. Nurses can help their patients make decisions on trying a new treatment or taking a new medicine based on findings.

These tests are data-heavy and a bit involved though calculators do the hard work. This is a topic for another day but here is an example of a typical problem a nurse may need to solve, either on the job or in a stats class:

Calcium is an essential mineral that regulates the heart, is important for blood clotting and for building healthy bones. The National Osteoporosis Foundation recommends a daily calcium intake of 1000-1200 mg/day for adult men and women.

While calcium is contained in some foods, most adults do not get enough calcium in their diets and take supplements. Unfortunately some of the supplements have side effects such as gastric distress, making them difficult for some patients to take on a regular basis.

A study is designed to test whether there is a difference in mean daily calcium intake in adults with normal bone density, adults with osteopenia (a low bone density which may lead to osteoporosis) and adults with osteoporosis.

Adults 60 years of age with normal bone density, osteopenia, and osteoporosis are selected at random from hospital records and invited to participate in the study. Each participant’s daily calcium intake is measured based on reported food intake and supplements. The data are shown below.

Is there a statistically significant difference in mean calcium intake in patients with normal bone density as compared to patients with osteopenia and osteoporosis? (Problem taken from sphweb.bumc.bu.edu)

If you want to see the work involved in the solution, check out the link sphweb.bumc.bu.edu

In summary, math can be very important for nurses! A true story that happened to one of my relatives who is a nurse.

She was about to administer a blood thinning medication to a patient in the hospital. She noticed in the chart that the doctor had already prescribed a different blood thinner in addition to the one he had ordered that she was about to give the patient.

She knew the normal dosing for blood thinners. She did not proceed. Instead, she called a pharmacist to double check the dosing with them and they confirmed that the patient should NOT receive both medicines.

She then made a note in the chart in alerted the other caregivers, including the doctor, of the change. Later in the day, he came down to thank her for catching his mistake!