When it comes to life and death situations, we want to have confidence in those that are taking care of us. How do they know when to give us medicine, or exactly how much we need? Rebecca Paisley has been a registered nurse for five years and describes her use of practical math in the workplace. 

Can you explain what you do for a living?

I work on an inpatient trauma unit. We take care of the patients once they are seen in the ER. The patients either go to the Intensive Care Unit, the Operating Room or come to our floor. We have a variety of patients – from car wrecks, falls, gun shot wounds, stab wounds, motorcycle wrecks, traumatic brain injuries and some very intense medical surgical patients with complex diagnosis. We care for these patients throughout their stay which can be from 1 day to months. We are constantly on the go, getting patients out of bed, doing procedures at the bedside (extensive dressing changes, chest tube insertions, general patient care), occassionally transfering patients to ICU, if they need a higher level of care. We also admit and discharge patients throughout the day. Needless to say, we are busy!

When do you use basic math in your job?

I use math every single day at work. It’s basic math (simple multiplication, division, addition, subtraction), but I have to use it to take care of my patients. Mainly it’s medication related. For example, you’ve got Tylenol 1000 mg ordered, but the patient needs to use a liquid form (650 mg in 20.3 mL) of the medication, you then have to figure out how many milliliters you need to give the correct dose. Once you do the math a couple of times, you remember the mLs that you need. It’s easy to do it that way with a rountine medication, but sometimes we are doing the math extremely fast in an emergent situation (like a chest tube insertion or code situation). We always double check the medication during these times with a second nurse. Another example is when we give pain medication. Say the patient has diluadid ordered our standard protocol is 0.3 mg to 0.9 mg per dose. Using our judgement, we decide on the dose amount. The medication is stock in 2 mg per 1 mL vial. By using basic division I know that the concentration is 0.2 mg per 0.1 mL. I also use it to figure out the drip rate for IV fluids and antibiotics. Ancef is ordered, it comes in a 50 mL bag, it needs to infuse in 20 minutes. Here is the math in my head: 60 minutes (1 hr) divided by 20 is 3. Multiply 3 by 50 (the mLs needed to infuse) and you get 150 ml/hr. Or if we need to bolus some IV fluids, but the doctor wants them over a certain amount of time. Say 500mL over 4 hours, (500 divided by 4 equals 125, so 125 ml/hr). I also use math to estimate my time spent with my patients in the morning (15-20 mins a patient, totaling 1 hour to 1 hour and 20 minutes ), so I can grab my morning cup of coffee! 🙂  However, this math is not always correct!

Do you use any technology (like calculators or computers) to help with this math? Why or why not?

We have certain medications that are continuous drips, like heparin or insulin. The pharmacy has calculators for these high risk medications for us to use. We just have to plug in the correct numbers, and we get the new dosing rate. The formulas for these calculations are available on our protocols, so if the calculators are unavailble (which rarely happens), we have the formula to use to get the new dosing rate. These calculators are used to reduce human error on these high risk medications. They are extremely important for safe patient care, ONLY as long as the nurse is plugging in the correct values! That’s why there is always a second nurse verification! Some of the medications (like the Tylenol example) will have the milliliters needed for the dose in the order information, but I like to challenge myself, and calculate the dose myself.

How do you think math helps you do your job better?

It makes my patient care more efficient. When I am able to do basic math in my head, I can administer medications faster, especially in an emergent situation where time is everything.

How comfortable with math do you feel? Does this math feel different to you ?

I feel pretty comfortable with math, but just basic math. The math I use at work has become “second nature,” so I’m able to use it and not really think about it. More complex calculations require good ‘ole paper and pencil!

What kind of math did you take in high school? Did you like it/feel like you were good at it?

I took geometry, and trigonometry, and I’m guessing Alegbra. I honestly hated math in school, but was fairly good at it. I never wanted to aspire to take calculus or advanced Algebra.

Did you have to learn new skills in order to do the math you use in your job? Or was it something that you could pickup using the skills you learned in school?

In nursing school, we had a pharmacology class, the whole first portion of it was math. We had to pass a math exam to even continue in the class. Everyone was so stressed out about it. We had to hand calculate drip rates, dosages, and do conversions. This math wasn’t foreign to me, as far as proportions and basic alegbra, but it was definitely stressful! Once we learned the “easy” ways to figure these calculations out, it was all good. I had to learn these new ways of solving these problems, it obviously did not come naturally!

Do you have a question for Becca? Send me your question and I will forward it to her.

Elizabeth Hanes, RN

Beth Hanes is a registered nurse in a plastic surgery center.  She takes care of patients before, during and after their surgeries.  Here’s how she uses math everyday.

What kind of math do you use in your job?

I use basic math for a lot of things, but probably the most important calculations are the ones related to medication use. Sometimes I dilute medication before giving it. For example, Promethazine needs to be diluted before it’s given in an IV. Using a 10mL syringe, I draw up 1mL of Promethazine and then add 9mL of normal saline (0.9% sodium chloride) to create a 10% Promethazine solution.

I also use basic math to determine, based on body weight, how much medication to administer. Medications are generally given on a milligram per kilogram basis. So, I convert a person’s weight in pounds to weight in kilograms (divide pounds by 2.2 to obtain kilograms), then I multiply this number of kilograms by the number of milligrams per kilogram to get the correct dosage. For example, Lidocaine might be ordered as 1mg/kg. A 220-pound patient weighs 100kg, so the correct dosage is be 100mg of Lidocaine.

How do you do your calculations?

I do use calculators because they’re typically faster, but I think it’s important to know how to do math by hand. I usually don’t have a calculator on hand in the operating room! Also, it’s critically important for me to have basic formulas memorized (such as how to convert pounds to kilograms). Without that knowledge, having a calculator or not is irrelevant.

Why is math important for your job?

Math skills help me ensure patient safety. There was a highly publicized case a few years ago in which actor Dennis Quaid’s infant twins were administered a very high dose of Heparin. This error occurred for many reasons, but one key factor was doing the math involved. This is a classic case of calculating dosage based on weight, and obviously errors were made in that calculation. In nursing, if you misplace a decimal point, you can kill someone.

When it comes to math in nursing, I think the main thing is to be very careful about calculations, double-check them, and then have someone else double-check them. No matter how good you may be at math, anyone can misplace a decimal point when calculating on-the-fly. It’s much better to take the extra seconds to have someone review your calculations and keep patients safe than to have any sense of ego about your math ability and endanger a patient.

What kind of math did you take in high school?

I had a rather sketchy math education, because my parents moved around a lot, and I only made it through Algebra II. On the other hand, advanced math was not yet common at the high school level when I was that age. Calculus, for example, was a college course. I did not feel I was good at math in high school. However, this “low math esteem” led me to focus on practicing real-world math skills.

These days, I am fairly comfortable with math, in general, though I frequently have to think through conversion problems, which are common in nursing. I find I often want to divide when I should multiply, for instance, so I have to be careful about that! Once I have a formula memorized, however, I feel very comfortable substituting variables with real values and arriving at the correct answer.

If you have questions for Beth, ask them in the comments section.  Oh, and today, June 20, is her birthday!  So take minute to wish her a happy day!

Read other Math at Work Monday entries in the archive.  And if you or someone you know wants to be interviewed for this regular, Monday feature, let me know.