How do I read the volume markings on a ringer's lactate solution bottle?

October 9, 2022 12:47 PM

Am at a milestone in my life as a pet owner: i have to administer daily subcutaneous drip. I have the target dosage, i have the instructions, but the vet overlooked to review how to read the volume markings for me, and I forgot to double check, because as it turns out, there are two rows of volume markings. For something so basic, my search results are giving too little information or too much about IV management. If I have to give 200ml, which row should I be reading?

Description: The sodium lactate solution bag has two rows of volume markings. One row header says Open; the other Closed. (I can't provide any online photos that has the back of the bottle.) Maximum volume is 1L. One row is marked equally between each 100ml. The other row isn't but clearly in some kind of calculated increase. When it's positioned correctly to begin the drip, for this row, the first 300ml from the maximum level have the smallest intervals between them. Then the distance to the next 100ml gets longer and longer.

I am very surprised how hard it's been to find this one piece of advice. Search terms I've used:
- how to understand the measurements on the ringer lactate solution
- how to read the measurements on the ringer lactate solution open closed
- why iv bag ml markings different open closed
- why iv bag volume markings different open closed

Bonus answers appreciated on reminding me what's the best medical or physics (for liquid volume stuff) terms I should use next time. And/or the logic for the different rates being marked on the bag so I can work it out next time.

posted by cendawanita to Pets & Animals (7 answers total)

If it were me, I would call up the vet's office and ask.
posted by aniola at 1:24 PM on October 9, 2022 [3 favorites]

Best answer: I am not your vet, but I recently had to give subcutaneous fluids to my dog.

My bags only had the unevenly marked rows. If the bag starts out with 1 L in it, administer down to the 800 ml line to give 200 ml. I believe the rows are marked unevenly because when hanging, the bag is not a uniform cross-sectional shape.

On edit: aniola's advice to call the vet is good
posted by A Blue Moon at 1:27 PM on October 9, 2022 [2 favorites]

A bit of a sideways solution, but if you have a digital kitchen scale and the solution has the consistency of water, a friendly reminder that 1 ml of water weighs 1 gram, so you could, using the tare function, weigh out 200g (i.e. 200ml) of solution and see where that gets you on the bag and figure out which set of markings to use.

(Technically if it's not pure water it won't be exactly 1ml = 1g, but unless it's substantially thicker or thinner it will be close enough, and if you're measuring by volume you'll never get exactly 200 ml anyway.)
posted by andrewesque at 1:43 PM on October 9, 2022 [4 favorites]

You might have a syringe, or a measuring cup marked with metric units. You could drain the bag in a controlled way (marking the before and after levels on the bag in Sharpie), to get a sense of how the output (in your measuring cup) matches the markings (on the bag).

Could you post a photo and/or any exact make/model information you have on the bag?

Alternatively, poke around on YouTube looking for people (e.g. that one guy I found that one time, but more of them) demonstrating how to do this; one of them might have the same kind of lactated Ringer's you do and might explain how to read the markings.
posted by amtho at 2:51 PM on October 9, 2022

Best answer: We've been doing subcutaneous fluids (aka sub-q) for our cats for years. Use the lines that are unevenly spaced. To read, grab either side of the fluid bag, right around where your fluid line is, and stretch the bag horizontally (gently). Your fluid will then show a clear line, which will be your reading for your starting/stopping point. So if you start and the fluid is at or above the 1 line, and then you administer fluids, and after you've given it a few minutes the new line is at 8 then that means you've given 200-ish ml.

We always found that reading it that way was really annoying and was mostly guessing to the nearest 50 ml, so we switched to a hanging kitchen scale (to weight fish, apparently!) and that has worked out to be much easier for us.
posted by tinydancer at 3:21 PM on October 9, 2022 [4 favorites]

Response by poster: Thanks all, and maybe I should look into those weighing scales. In the meantime, the vet is closed on Sundays and today (Monday) is a public holiday, hence my internet search, confusion, and subsequently, this Ask.
posted by cendawanita at 7:26 PM on October 9, 2022

Ditto, if this is a hanging bag o' drug thing. When it's full it will drain faster because there's more there (all shape and pressure wise) so the markings will be closer. When it's near empty it will drain slower (lower pressure and smaller volume) and the lines will get farther apart.

If it's a bottle and not a bag.... same thing applies. One is calibrated for Closed so you can tell about how much you have left. The other is calibrated to show the rate due to volume left and shape of the container.

Are the scales backwards? I'd expect they were with a bottle ((I can't provide any online photos that has the back of the bottle.) ). I would expect them to go backwards to each other, one for on the shelf (Closed) to read what's left, the other (Open) for the inverted case where it's going into the body.
posted by zengargoyle at 8:16 PM on October 9, 2022 [2 favorites]