Real World Med Math Problem

[Music in My Heart]

Often times, when "med math" is discussed, someone will pipe in with something along the lines of "well, the pharmacy actually does that... we just verify it," or "we use 'smart pumps.'"

Here's a real-world example from yesterday...

Ambulance delivers a patient who'd taken a header from the third floor balcony... obvious severe head trauma...

The patient gets intubated and needs to go to the scanner STAT. He's just starting to brady down a bit, "Bolus him 75 grams of mannitol and get him to the scanner now."

Our pyxis holds mannitol available as 20% mannitol in 250 mL of D5W.

What do I do?

++++

Think about and I'll post the answer in a bit...

[NewYorkerGirl]

I'm clueless. How many grams are in the 250?

I'm clueless. How many grams are in the 250?

Yep, that was my first question as I'm looking at the bag while the doc's going "alright, let's go..."

What I started with was that, generally, meds are stocked in useable quantities... generally the supplied amount is in the range of what's commonly given (with the notable exceptions of drips like dopamine, heparin, insulin, etc). So I'm looking at the bag thinking... this has to be close...

The answer begins in what means "20%"

[Roman1]

20% mannitol is 20grams per 100ml, so 250ml bag has 50grams mannitol, so would bolus the 250ml bag plus 150ml from another 20% mannitol in 250ml. I think that's it?? But may be wrong

[smf0903]

I say 375 mL for bolus

20% solution would be 50g/250mL so...

250mL/50g * 75g= 375mL

And that's my final answer...

[Madras]

A little help from Dr. Google:

20% Mannitol Injection USP is a sterile, nonpyrogenic solution of Mannitol USP in a single dose container for intravenous administration. It contains no antimicrobial agents. Mannitol is a 6-carbon sugar alcohol prepared commercially by the reduction of dextrose. Although virtually inert metabolically in humans, it occurs naturally in fruits and vegetables. Mannitol is an obligatory osmotic diuretic.

Each 100 mL contains:

Mannitol USP 20 g; Water for Injection USP qs

pH: 5.3 (4.5–7.0); Calculated Osmolarity 1100 mOsmol/liter

:blackeye:Grab more than one bag!!

[smf0903]

And by the way, this post makes me think of first semester when we first started learning med math. Our instructor told us...drilled it into us...that we need to know how to figure things out, even those things the pharmacy "normally does" and gravity drips (even though we have smart pumps). She was a nurse who went to help out after Katrina, and she said there were nurses there who didn't remember how to figure gravity drips (or didn't know...either way couldn't figure them out). So we had it drilled from day one never to say "well the pharmacy does that" or "we just set the pump". Good thread!!

A little help from Dr. Google:

Ah yes... but in the midst of it, Dr Google is decidedly unavailable... as is Dr. Lexi-Comp who is much more reliable and thorough.

Yes, yes!

Y'all get it!!

Percent = per 100...

20% is 20 grams per 100 mL (which is also in fine print on the bag)...

so 200 mL is 40 grams...

so 250 mL is 50 grams...

so 25 grams is 125 mL...

so total vbti is 375 mL or 1-1/2 bags

Real-life stuff here... know your math... it counts...

Oh, and the obvious question...

Why did the doc want him to get 75 grams of mannitol ASAP?

[smf0903]

Oh, and the obvious question...

Why did the doc want him to get 75 grams of mannitol ASAP?

To decrease ICP? Since he had head trauma?

To decrease ICP? Since he had head trauma?

Very good...

So, a few other questions:

1) The guy was GCS 6 on arrival and intubated immediately. ED and Trauma docs didn't order a sedation drip... despite the fact that paralytic and anesthesia were short-acting... why not? (hint... any other assessments needed?)

2) What other meds were ordered in quick succession after returning from CT?

3) What other MD intervention did we need to get set up for?