Dosage calculation question

Published

I'm practicing some dosage calculation questions for my class this question has me confused. Order:Ampicillin 100mg/kg/day IM divided in 2 doses. Weight:3.778kg. Dose on hand:Ampicillin 250mg/3ml. How many ml of ampicillin does the nurse administer for each dose? I answered 2.3ml per each dose but the correct answer is 2.27 ml per each dose. I thought that if the volume was greater than 1 ml the dose can be rounded to the tenths position? I'm sure if they rounded this way because the patient is a pediatric patient. Also it would seem difficult to draw up 2.27ml of medication in one syringe. I just want to know how other people would answer this particular question.

Up Vote Up Vote ×
Specializes in Nurse Leader specializing in Labor & Delivery.

There's the "book" and there's the "real world" answer. The book answer is 2.27 (or whatever is your school's policy on rounding). In the real world, you would administer 2.3 ml, because 2.27 would be impossible to draw up.

Up Vote Up Vote ×
Specializes in SRNA.

If the question specifically state "round to the nearest tenth, whole, etc" then I round. If it doesn't say to round, I don't round. In that question it doesn't say to round so I'd say 2.27 mL.

Up Vote Up Vote ×

Thanks I was confused on that being the answer. I assumed since the volume was greater than 1 ml that it should have been rounded to the tenths position even though it is a pediatric patient

Up Vote Up Vote ×

Your instructor should have provided you rounding criteria for use in her or his class. In the absence of such criteria, he or she should accept responses that will be employed in actual practice. As Klone wrote in her post, in actual practice the volume to be administered would be rounded to the nearest 0.1 mL, the gradation increment in most 3 mL syringes. In the problem you described, the difference in the dose administered, if you rounded to 2.3 mL is 2.49 mg.

If this were being administered IV, using a syringe pump you could use a syringe with 2.3 mL (191.67 mg) and program it to deliver the 188.9 mg (2.2668 mL) dose. As you are delivering this IM, this obviously isn't an option. This does, however highlight the more important consideration. As the maximum volume per injection site for newborns and young infants is 0.5 mL, you would have to deliver this dose in five separate injection sites. And your going to do this twice a day?

When I precept new nurses or nursing students I stress the importance of questioning their answer when it doesn't make sense. Giving an infant a dose of any medication that requires five separate injection sites should be questioned. When students are given problems where this is the "correct" response, they never learn to question answers that just don't seem right.

Just another example of an instructor writing a question that just doesn't make sense.

Up Vote Up Vote ×
Specializes in Pedi.
Your instructor should have provided you rounding criteria for use in her or his class. In the absence of such criteria, he or she should accept responses that will be employed in actual practice. As Klone wrote in her post, in actual practice the volume to be administered would be rounded to the nearest 0.1 mL, the gradation increment in most 3 mL syringes. In the problem you described, the difference in the dose administered, if you rounded to 2.3 mL is 2.49 mg.

If this were being administered IV, using a syringe pump you could use a syringe with 2.3 mL (191.67 mg) and program it to deliver the 188.9 mg (2.2668 mL) dose. As you are delivering this IM, this obviously isn't an option. This does, however highlight the more important consideration. As the maximum volume per injection site for newborns and young infants is 0.5 mL, you would have to deliver this dose in five separate injection sites. And your going to do this twice a day?

When I precept new nurses or nursing students I stress the importance of questioning their answer when it doesn't make sense. Giving an infant a dose of any medication that requires five separate injection sites should be questioned. When students are given problems where this is the "correct" response, they never learn to question answers that just don't seem right.

Just another example of an instructor writing a question that just doesn't make sense.

Yes, this. The patient weighs 3.778 kg so we can assume it is an infant. You cannot administer 2.3 mL IM to an infant in one injection. I've also never seen ampicillin ordered IM in 11 years of pediatric nursing.

Up Vote Up Vote ×

In order to deliver 2.27 ml it would require you use two syringes It makes more sense to round the dose. I was taught round the dose according to the syringe in this case it would call for a 3ml syringe which has 0.1 ml marking so the dose would be round up to 2.3 ml

Up Vote Up Vote ×

When performing my dosage calculations I do not round anything until the end. When I do round, I round according to the equipment i'm Using in this case it you would use a 3 ml syringe and round to the tenths position since a 3 ml syringe has 0.1 ml markings. I'm not sure why the answer was 2.27 ml. I guess they are expecting you to draw up that dose using multiple syringes

Up Vote Up Vote ×
+ Join the Discussion