Help With Weight dosage problem

Mike R, ADN, BSN, RN · Aug 13, 2011

You'll set it up like this:

(4.4mg/1kg) x (1kg/2.2lbs) x (80lbs/1) x (250ml/200mg) x (1/4hr) = answer

Docs ordered dose X conversion factor X pt's weight X available meds= ml's to give. The last one sets up the rate.

I have the answer but I want to see if you can figure this out, given I basically showed you all the work

MN-Nurse, ASN, RN · Aug 13, 2011

Hi I have a problem that I need help with . My teacher uses the DA way an I do not . Can someone help me please !!!
Vibramycin 4.4mg/kg IVPB daily is ordered for child weighing 80 lbs The premixed bag is labled 200mg/250 ml D5W to infuse in 4 hrs calculate the flow rate ml/h

The reason your teacher uses the DA way is so they don't have to monkey around with formulas. It is OK if you want to use the formula method, but you have to know how to apply it and figure out what you need.

On this problem, there is no single formula to drop numbers into, so lets look at the problem and see what information you need.

It looks like it's asking for a flow rate. So what's that? It's volume/time right? Good. So what do we know? Looks like they gave us the time - 4 hours. Neat. Halfway there.

What else do we need for the rate? Oh yeah, the volume. Now how do we get that? Well, we could use a formula for that, and I think it's one you know: D/H * Q = G (Desired / Have x Quantity = Given)

So what do we know in that formula? Well we sure know what we have: 200mg/250ml. (200mg is the Have, 250 ml is the quantity)

We just need to know what the Desired dose is. You figure that out by converting the weight to kg then multiplying by the factor you are given (4.4mg/kg). That gives you the D.

You now have everything you need to solve the problem. Plug in your D, H, and Q to get the Given amount (which will be in ml) then divide that by the time they already gave you and you have your answer.

Now your other option is to learn DA and do the problem all in one step like a previous poster did.

Good luck!

LadyinScrubs, ASN, RN · Aug 13, 2011

hi i have a problem that i need help with . my teacher uses the da way an i do not . can someone help me please !!!
vibramycin 4.4mg/kg ivpb daily is ordered for child weighing 80 lbs the premixed bag is labled 200mg/250 ml d5w to infuse in 4 hrs calculate the flow rate ml/h[/quote]
i prefer working it out the long way. this provides me more control, but i can understand why some use da. i read the question completely and then find out what the question wants. it wans the flow rate in ml/hr. then i work the question.
1. convert the pt's lb weight to kg weight
2. i plug in the pt's kg weight into the formula: 4.4 mg * pts weight in kg. answer is: ___ of mg's
3. i use ratio and proportion to solve the formula.
200mg/250ml * ___mg (from answer to #2 above) / x ml
solve for the missing x and
you will have ______ ml
4. you need to do the flow rate
answer: ___ml's (answer from 3 above) to infuse 4 hrs
how many mls per hour: __ml (answer from 3 above) / 4 hrs = ____ ml flow rate per hour via iv pump

trudiegrl · Aug 14, 2011

Just out of curiosity (only because I've been practicing DA with online questions like these, is the answer 50 mL/hr?

Missjlockettspn · Aug 14, 2011

thanks my problem is with the time how do i know the 4 is on the bottom ?

Missjlockettspn · Aug 14, 2011

thanks for the help , i kno its a lot of work but i understand this better

Missjlockettspn · Aug 15, 2011

thanks for the response when i did it this way i got the answer an understood the process

trudiegrl · Aug 15, 2011

thanks my problem is with the time how do i know the 4 is on the bottom ?

It's indicated in the problem that the bag has 250 mL per 200 mg infused in 4 hours.

When I set up my solution. I always start with the ANSWER unit which is mL/hour. And conveniently the problem gives you 250 mL (goes on the top) and 200 mg/4 hours (goes on the bottom).

This is how I set up my problem

(250 mL/ 200 mg/ 4 hours) x (4.4 mg/ 1kg) x (1 kg/ 2.2 lbs) x (80 lbs) = 8800/1760 = 50mL/Hr

All units crossed out except the answer units which is ml/Hr for rate of infusion.