Medical Dosage Calculations - In Your Head or Calculator?

Katie5 · Oct 21, 2009

If u have a calculator, what's to stop u from using one. And also having someone else verify your answer.

AlabamaBelle · Oct 21, 2009

Every one in our unit uses a calculator. With barely enough time to go to the bathroom, it doesn't make sense to use pencil and paper. I have always been notorious about making ridiculous little mistakes. I love calculators. I can do calcs without a calculator, but it's just so much simpler with one.

miss81, BSN, RN · Oct 21, 2009

I have my calculator in my pocket all the time... if I have it then why not use it??? Then I can be SURE that my "zeros" and decimal points are in the right place. Sometimes technology can be our friend, especially when peoples lives are at stake!

CharlieT · Oct 21, 2009

As my p'cology instructor would say:

"here are some calculators for you to use, you can use mine, use your own, work it on paper, or work it in your head, show me you work or don't show me your work. I don't care. Just give me the right answer."

Somehow I don't think that our patients care either, they just want/need the right answer. At the end of the day, the patient is what we should be concerned about, right? It seems to me that if a nurse needs a calculator to find the answer, then that's ok, as long as he/she gets it right. You can buy a calculator for 3-4 bucks and it only takes a second to plug in the numbers, so there is no real cost savings for not using a calculator. I understand what you are saying about the poor math skills of the current generation, believe me I understand what you are saying. I enjoy this kind of thing sometimes when I pay in cash. I give them a strange amount to see how well the youngster can handle the mental calculation if the register is not one that calculates the change for them. Its fine to torment a cashier with mental math Please, let's not torment the young nurse with mental math before he/she pushes morphine sulfate or some such into me or mine. As Katie said, having someone else to double check is a good practice.

nursemike, ASN, RN · Oct 21, 2009

Paper towels. Unless it's just incredibly simple, like 50mg of a 100mg tablet. The most common calcs I do are heparin gtts, and I wouldn't trust a calculator or doing it in my head. Also, it's supposed to be verified by a 2nd license, so it's a lot easier if I can show them my work.

Sometimes I'll get a piece of paper from one of the printers, but usually it's a paper towel. When I was a carpenter, most of my "blueprints" were on scrap lumber.

readytoroll · Oct 21, 2009

I usually write mine down when I have to calculate something. That being said, whether you use a calculator or not, you have to know the formula. The calculator just speeds things along.

belgarion · Oct 21, 2009

Having a heavy math background I always just looked at the problem on a test and wrote down the answer and never missed a calc problem on a test. I still do them that way at work but I do have enough sense to get someone to verify my answer. So far I've never been wrong there either but I figure the first time I don't get someone to check will be the big one. Why take stupid risks?

TiffyRN, BSN, PhD · Oct 21, 2009

I work NICU, we do a lot of tiny precise calculations. Almost everything that we double check each other on is done some with paper and pencil, some with calculators. We write out our equations and use the calculator for the "heavy lifting". The most important thing is to know the right equation (or some people use dimensional analysis, which I know nothing about). But as someone else said, as long as 2 people arrive at the right answer. . .

A few things we do completely in our heads, one is ampicillin which is mixed 100mg/ml and (typically) dosed 100mg/kg. So we will hold up our med vial showing Amp 100mg/ml then pull up the 0.95ml to show 95mg dose. That is probably one of the few med calculations that most don't use a calculator.

Sometimes if I have an infant several days in a row, I may keep my report sheet (with my equations on the back) when the infant receives the same med over and over and show it when I get someone to check me.

EmergencyNrse · Oct 21, 2009

during my stint in nursing school (1980's) our med dose calc class was about six weeks long, show all work, use formulas provided by instructor only, and totally in our heads (or scrap paper, *lol*), no calculators allowed. the floors/units one worked on at the time as a na rns young and old also did everything in their heads as well, right down to drip rates.
otho am hearing today many schools allow calculators and many hospitals have systems to do the "work" and of course pumps can be programmed. however have also heard that some places do not have these systems and or still require all drips to be calculated out by hand/head regardless of availability of pumps.

there are a couple thoughts here. i hope i can keep them straight and make sense. my mind is going 100 miles/hr.

this is one of my pet peeves.

you know, this is actually a great thread. most recently i have seen a trend to go completely and totally to pump control only. ivac & alaris pumps actually have lockouts where you input sensitive medications into the pump and it controls your drip rate and does your calcs for you.

now, there aren't enough pumps to go around. traditionally we reserved the pumps for micro drips and medicines that require a slow infusion rate right? now the expectation is that all fluids be on a rate controlled pump... um, but there aren't enough pumps :banghead: and... they aren't always calibrated correctly.

not only that but i was going over drip rates with a new grad and she didn't know that there were different drip chambers that control flow. 10gtt/ml vs. 60gtt/ml. no clue about standard sets and vented sets. she told me that they didn't even teach them about drip rates. she couldn't do it. really, i'm not kidding. new trend? i'm thinking wow...just wow. :eek:

next is actually doing calculations. i went through the process of orienting many new grads. the formulas they are teaching are about ratio/proportion. okay, so the math works but can you tell me what the concentration is per ml? no! sure can't. the figures come out right but to draw it up there is no understanding what they are administering.

i keep it simple and am no means trying to "sharpshoot" them while orientating. i'm evaluating their knowledge and attempting to teach them right? so much easier to know your concentration per ml. plez' to lem'me 'splain.

tylenol-

to make it easy here lets say child is 6.4 kg.

pediatric dose is 15mg/kg q4.

concentration is standard 160mg in 5ml tubs.

out comes this scratch paper, a calculator, and a mathematical equation/explanation on paper that would make albert einstein proud... all to come out with an answer of 3. an entire page of ratio & proportion. no concept that there is a specific dose there. how much medicine per ml? dunno she tells me. how much are we giving? 3. no, how many milligrams? dunno. i asked if she ever thought about it? no, i just do the formula. this happen to anyone else out there?

i asked her if she could see that 160mg:5ml was just 32mg/ml and that 6.4 kg child that you are looking at 96mg and 3 ml's? no, i can't do it that way...

soooooooo many additional medications that are easy to does if you know the answer in ml's to include gtt-rate.

no critical thinking whatsoever and absolutely no dosing anything without a calculator. :no:

people are going to go off again about how i'm an us vs. them personality and how i just hate the next generation but this is serious and so am i. there is a knowledge deficit here and it's scary. many new grads are not functional and it's not all their fault. mandated formulas are okay for facts & figures but where is there actual thinking???

i hope some of you pause for a little bit and think about it. calculators are fine but you need to use your head!:spbox:

AugustRain · Oct 21, 2009

Calculators are fine but you need to use your head!

I think this is key. Personally, I know that mental math is not my strongest point, never has been, so I always use a calculator. It makes me more secure to have the double check. That being said, I have to understand the process of what I'm doing in order for the calculator to be of any value. It's also my responsibility to know if my answer makes sense or not. Just because I come up with 100 mL as an answer doesn't mean I should go ahead and give it if I know that 10 mL makes more sense. I still have to know what's safe, the calculator is just a tool.

diane227, LPN, RN · Oct 21, 2009

I always use a calculator and usually double check my dose with another nurse unless it is something simple.