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Discussion

HELP!!!!! Math is KILLING me!

Ok, so here are my questions, I just need someone to show me the formulas, and I can work them out myself...

1)

Order: Infuse 1 unit (250ml) PRBCs in 3 hours. You remember that the blood should infuse at a rate of 50ml/hr in the first 15 minutes.

Available: Blood tubing with a drop factor of 15gtt/ml

How many gtts/min should the PRBCs infuse for the first 15 minutes?

How many gtt/min should the remaining blood infuse?

2) The DR orders to start an Aminophyllin drip @ 5 mg/hr. The aminophyllin you have on hand has a concentration of 25 mg/ml. How much aninophyllin would you add to a 500ml bag of d5 1/4 NS to infuse at 10ml/hr?

Like I said, I only need formulas, Id prefer to figure it out on my own. I really gotta learn this, my test is Wednesday.

Featured Replies

For problem #1 the formula is: Volume/Time X drop factor

Can't help with the second problem, but I'm curious as to the formula to use. Good luck on your test.

  • Author

so the answer to the first part of #1 would be 15 because gtt/min is equal to gtt/ml right?

That's what I get

ML/hr x DF =

gtts

Ml x DF =

mins

50 / 15 x 15 = 49,9

So the rest of your blood would be 200 / 165min. x 15 = 18gtts

I believe ??

For Aminophyllin

D (dose or Dr.'s order)

Hand (what you have on hand)

V (volume or quantity)

D x V = 0.2

H

This one is a little tricky, because the MD's order is 5mg, per hour. Meaning he would get 0.2ml so...a 500cc bag, to infuse 10ml and hour

The bag will run for 50 hours at that rate, if you want to to get 0.2ml of aminophyllin every hour, it's 0.2 x 50, so 10ml is added....

I think, let me know if I'm wrong......good luck! Interested to see

  • Experts
Order: Infuse 1 unit (250ml) PRBCs in 3 hours. You remember that the blood should infuse at a rate of 50ml/hr in the first 15 minutes.

Available: Blood tubing with a drop factor of 15gtt/ml

How many gtts/min should the PRBCs infuse for the first 15 minutes?

Here is the set-up by dimensional analysis:

50ml/1hr
(amount to be given)
x 1hr/60min
(time conversion factor)
x 15gtts/1ml
(drop factor of tubing)
= 750gtts/60min
, and simplifying further and rounding,
13 gtts/min.

How many gtt/min should the remaining blood infuse?
Amount of blood remaining is 200ml. Amount of time remaining is 2.75 hours.

200ml/2.75hr
(amount to be given)
x 1hr/60min
(time conversion factor)
x 15gtts/1ml
(drop factor of tubing)
= 3000gtts/165min,
and simplifying further and rounding,
18gtts/min.

The DR orders to start an Aminophyllin drip @ 5 mg/hr. The aminophyllin you have on hand has a concentration of 25 mg/ml. How much aninophyllin would you add to a 500ml bag of d5 1/4 NS to infuse at 10ml/hr?

This is a ratio problem:

10 ml
(final solution concentration per hour)
/5 mg
( final Aminophyilline concentration per hour)
= 500 ml
(total amount of D51/4NS)
/X mg of Aminophylline

Cross multiply. Answer is

250 mg Aminophylline
needs to be added to the 500 ml bag of IV fluid. If you think I'm wrong, check it. Dose desired (5mg) divided by dose on hand (250mg) times the amount the dose is in (500ml) = 10 ml

Here is the set-up by dimensional analysis:

50ml/1hr
(amount to be given)
x 1hr/60min
(time conversion factor)
x 15gtts/1ml
(drop factor of tubing)
= 750gtts/60min
, and simplifying further and rounding,
13 gtts/min.

Amount of blood remaining is 200ml. Amount of time remaining is 2.75 hours.

200ml/2.75hr
(amount to be given)
x 1hr/60min
(time conversion factor)
x 15gtts/1ml
(drop factor of tubing)
= 3000gtts/165min,
and simplifying further and rounding,
18gtts/min.

Actually, for the second part of the question the blood remaining is not 200 ml. But 237mL. Blood already infused (mL) = {infusion rate (13gtt/min) x 15 min (time elapsed)} / 15 gtt/mL = 13 mL

250mL -13mL = 237 mL (blood remaining)

50 mL is the amount that would infuse in 1 hour, not 15 minutes.

237ml/2.75hr (amount to be given) x 1hr/60min (time conversion factor) x 15gtts/1ml (drop factor of tubing) = 3555gtt/165min, and simplifying further and rounding, = 22 gtt/min.

Hope this helps! :)

  • Author

Thanks you all, I got some formulas from class mates and using your all's so that I can figure out which way is the best way for me.

  • Experts
Actually, for the second part of the question the blood remaining is not 200 ml. But 237mL. Blood already infused (mL) = {infusion rate (13gtt/min) x 15 min (time elapsed)} / 15 gtt/mL = 13 mL

250mL -13mL = 237 mL (blood remaining)

50 mL is the amount that would infuse in 1 hour, not 15 minutes.

237ml/2.75hr (amount to be given) x 1hr/60min (time conversion factor) x 15gtts/1ml (drop factor of tubing) = 3555gtt/165min, and simplifying further and rounding, = 22 gtt/min.

Hope this helps! :)

Wow! You're right! Incident report for me!

OMG, I'm so glad I've taken my last math test. Just reading those problems made me start sweating. LOL I know I will always need to have the knowledge of how to do the math, and I passed all my math tests, but it still makes me very nervous!!

  • Author

100% baby!!!! In other words, no more math tests for Melanie!!!! :balloons:

100% baby!!!! In other words, no more math tests for Melanie!!!! :balloons:

That's great! Congratulations!!

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