Mastering dosage calculations is absolutely necessary in nursing school. If you are just starting your program, you will most likely have a dosage calculations exam sometime in the first weeks of class…if your program was like mine, you had three attempts to get 100% on this exam or you were out of the program. And since your ability to accurately give your patient the ordered dose of any medication could mean the difference between life or death, you can see why this is a pretty crucial skill. So, if you need to learn (or re-learn) how to do dosage calculations the 100% foolproof way, check out this post. Then come back here and take this quiz to put your skillz to the test. Ready?
Question #1 (easy)
You are working night shift with a nurse who makes the strongest coffee ever. The good news is, this rocket fuel concoction keeps you alert and cheerful all night long. The bad news is, it wreaks havoc on the digestive system of anyone who dares drink it. The last time you worked with this nurse (and drank his coffee) you had to use a patient’s bedside commode in order to prevent a sizable and embarrassing situation from occurring all over the floor. It is 2am and your eyelids are getting heavy. You want to drink the coffee, but you’re also wearing your favorite scrubs and don’t want to risk any accidents. You talk to one of the GI docs about your dilemma and she prescribes 15mg GutLove to be dissolved in each pot of coffee. GutLove comes in 3mg tablets. How many tablets of GutLove will you sneak into the coffee pot?
Question #2 (easy)
You get home from a long shift to find your roommate binge-watching Real Housewives. She barely acknowledges you and you go straight to your room to hang out with your cat. The next morning, she is still watching the housewives do whatever it is they do. She’s in the exact same position, drooling out one side of her mouth and babbling incoherently. You call 9-1-1 and the paramedics arrive with a state-of-the-art medication called BrainRenew. You’ve read about this drug and know that the standard dose of BrainRenew is 50mg/kg IV. Your roommate weighs 132 pounds. How many mg of BrainRenew will she require?
Question #3 (easy-ish)
You are taking care of a patient with the most impressive back hair you have ever seen. The problem is, it’s the only hair on his entire body. From the front he looks like an undefined blob of flesh. From the back, he looks like Sasquatch and it’s starting to terrify the children in his neighborhood. You see he’s been prescribed 1500mg/kg HairGoThere IV, q 6 hr in an attempt to get his body hair to grow in the appropriate places. HairGoThere comes in a vial of 4000mg to be reconstituted with 10ml D5W. Your patient weighs 116 pounds. How many ml of HairGoThere will your patient receive in a 24 hour period (round to the nearest tenth)?
Question #4 (a little trickier)
You receive report on a 16 year old girl admitted to the hospital for temporary blindness secondary to rolling her eyes repeatedly. It seems she has managed to roll her eyes so far back they’ve become stuck and it’s up to you to save her. The opthamalogist on call prescribes 25mcg/kg/min EyeRollz via continuous IV infusion until vision is restored. EyeRollz is available in a 500ml bag containing 500mg of medication. Your patient weighs 112 pounds. For how many ml per hour will you program your pump, rounded to the nearest tenth?
Question #5 (last one!)
You are keeping VERY strict I/O on a critically ill patient in renal failure and heart failure. The physician has ordered a total of 100ml per hour of ALL fluids, including a maintenance fluid of D5 1/2NS to be run at a variable rate to maintain 100ml/hr TOTAL. She weighs 143 pounds. At what rate will you run the NS during the 1600-1700 hour (rounded to the nearest whole number)?
Below are the patient’s current IV medications:
- KidneyLove to start at 5mcg/kg/min titrated by 2mcg every sixty minutes to a max dose of 15mcg/kg/min. The dose started at 1400 and it is now 1630. KidneyLove comes in a 250 ml bag containing 500mg of medication
- HeartLove 150mg q 4 hours. The last dose was given at 1615 and consisted of 150mg medication in a 50ml bag.
- PainBeGone 4mg IV. PainBeGone comes in a 10ml vial containing 20mg of medication. You give her the prescribed dose, flushing her PICC before and after with 10ml NS.
Answers below….no peeking!
To ensure you don’t accidentally peek at the answers, here’s a picture of some kittens…answers below the cuteness!
#1: 5 tabs
#2: 3000 mg
#3: 791 ml
#4: 76.4 ml
#5: 10 ml/hr
I’ve gotten a lot of questions about #5, so I’ll talk you through it…ready? The first thing to know is that your TOTAL IV fluids are not to exceed 100ml/hr. Yes, you will sometimes get orders like this on very critically ill patients who are fluid overloaded or have serious heart failure or kidney failure. In order to do this question, we must figure out how much of each of her meds she is getting for that hour.
Step #1: Figure out how much KidneyLove she’s getting per hour. Note that this is a med that has been titrated at regular intervals. So, if the dose started at 5mcg at 1400 and is going up by 2mcg every sixty minutes, how much will she be getting in the 1600-1700 hour? Well, at 1400 it was 5mcg, at 1500 it was 7 mcg and at 1600 it’s 9 mcg…so figure your ml/hr based on 9mcg/kg/min. Do your dimensional analysis and you’ll see she’s getting 17.55ml/hr of this medication.
Step #2: Determine how much HeartLove she’s getting in the 1600-1700 hour. This one is easy…just count the 50ml bag that the medication comes in.
Step #3: Calculate how much fluid she received with her PainBeGone medication. Do your dimensional analysis to figure out how many ml of PainBeGone you will draw up (the answer is 2ml). So add all those up! 2ml for the med, plus a 10ml NS flush before giving it and a 10ml NS flush after giving it…a total of 22ml.
Step #4: Add all those up: 17.55 + 50 + 22 = 89.55, rounded to the nearest whole number is 90.
Step #5: Take your TOTAL allowed IV fluids and subtract her meds. 100-90=10. You will run her maintenance fluid at 10ml/hr for that hour.
Tada! Got another dosage calc question that’s tripping you up? Maybe this is the problem…or, send it to me in the form below and I’ll walk you through it!