fluid calculations

RE: fluid calculations

Chris Geddes — Wed, 24 Jan 2018 14:51:54 GMT

Won't help with exams, but for real life, if you download the Norbrook app (search for Norbrook on Apple or Android app stores), there is a handy little calculator for working these calculations out.

I don't work for them (any more) so I have no commercial benefit, but I did develop the calculator when I did as I find it quite handy!

RE: fluid calculations

apache — Wed, 24 Jan 2018 14:30:24 GMT

Are you sure? If this is how you are taught for OSCEs then ignore me, but from the question I'd assume the cat was going to be on OVFT for 12 hours, therefore I'd want to give the 12 hours of maintenance (2 x 12 x 4 = 96ml) plus the entire deficit (240ml).

336ml required

336/12 = 28ml/hour

20 drops per ml so 20 x 28ml = 560 drops per hour

60X60 = 3600 (six sixes are thirty six so easy to remember) seconds in an hour

560/3600 = 0.156 drops per second

I use the inverse button (1/x) on the calculator to divide by 1 and gets 6.43, so one drop every 6 and a half seconds.

NB use a paediatric giving set in cats and it's a much more sensible 1 drop every 2 seconds!

RE: fluid calculations

anne ahern — Wed, 24 Jan 2018 13:10:19 GMT

A 4kg cat is presented suffering 6% dehydration from chronic losses. There has been no vomiting or diarrhoea and the cat's temperature is normal. The giving set to be used for fluid administration delivers fluid at a rate of 20 drops per ml. Work out the fluids required over a 12 hour period and show the rate of infusion in drips per minute.

ANSWER

Maintenance requirements

Weight of animal

4 x 50 = 200mls (per 24 hours)

Deficits

4 x 6 x 10 = 240mls (per 24 hours)

Ongoing losses

None

Total fluids required over 24 hours

200 + 240 = 440mls

Total fluids required over 12 hours

440 divided by 2 = 220mls

Minutes in 12 hour time period

60 x 12 = 720mins

Volume of fluid required per minute

220 divided by 720 = 0.31ml/min

Drip rate per minute

20 x 0.31 = 6.2 drips/min (This figure is usually rounded up to the nearest 10; so 6 drips/min)

This figure is usually rounded up to the nearest 10, so 6 drips/min.

Hope this helps!

Re: fluid calculations

Sandra Taylor RVN, MBVNA — Sun, 12 Sep 2010 15:06:07 GMT

[quote user="Carolyn Edwards RVN"]

[quote user="Sandra Taylor RVN, MBVNA"]

Jeez you guys make that so complicated!!!

[/quote]

I'm useless at remembering formulas so I need to know the reasoning behind calculations!

I have had to work it out backwards before now - someone else had started a drip and I knew when it had started and what the gap between drips was. From that I was able to work out how much the dog had been given. Don't know whether it was more accurate than guessing how much was left in the bag!

[/quote]

Just weigh the bag. That tells you how much is left.Whatever it says in grams... is pretty much what mls are left in the bag. You could be super accurate and weigh and empty drip bag, and take this away from whatever the weight says.

As to the formulas that one I use is

24x60x60.......24 is your hours, so if you need to give deficit over 6 hours say, you do the same calculation but replace the 24 with the 6

the x60x60 is obviously your minutes and seconds. So in most calculations you would divide these down, but that is time consuming , so you multiply them and divide the fluid amout by drip factor instead.... it's much quicker

Re: fluid calculations

Carolyn Edwards — Sun, 12 Sep 2010 14:22:03 GMT

[quote user="Sandra Taylor RVN, MBVNA"]

Jeez you guys make that so complicated!!!

[/quote]

I'm useless at remembering formulas so I need to know the reasoning behind calculations!

Re: fluid calculations

Sandra Taylor RVN, MBVNA — Sun, 12 Sep 2010 13:30:57 GMT

No Nick..... do the sum, you will see

Re: fluid calculations

Nick Shackleton — Sun, 12 Sep 2010 06:53:44 GMT

Sandra is it not times by drip factor NOT divide by drip factor???

Re: fluid calculations

Sandra Taylor RVN, MBVNA — Sun, 12 Sep 2010 03:17:13 GMT

Jeez you guys make that so complicated!!!

50mlxbw=total maintenance for a day. \divide by 24 gives you your ml/hr

use the formula

24x60x60/divide by total maintenance, then divide by drip factor. this gives you drops per second.

if you want dehydration etc let me know!

Re: fluid calculations

Catherine Raymond — Sat, 11 Sep 2010 23:26:38 GMT

Using Daily Allowance of 50ml/kg/day

Total daily allowance= 50mls/kg/day x bodyweight = A mls/day

Hourly Rate = A mls/day / ........ hours = B mls/hour

Drops per minute = (B mls/hour / 60 minutes) x .... drops/ml = C drops per min

If you then want to work out drops per second 60 / C

This would be for a straight forward case for prac exam for example. If there is vom/diarr then you would include this losses in the daily maintenance calculation (4ml/kg/episode)

If you are told that a patient is x% dehydrated then the fluid deficit would be calculated as

Deficit (mls) = (bodyweight (kg) x % dehydration ) x 10

So a 2kg cat that is 10% dehydrated the deficit would be (2kg x 10) x 10 = 200mls
this would then be added to the total daily allowance.

Well, that is how I do it!!

Re: fluid calculations

SharonSP — Sat, 11 Sep 2010 21:50:52 GMT

Carolyn has pretty much nailed it for you...Is this for an OSCE exam because the calculation is more basic.

i.e. calculate maintenance 50mls/kg but if the task states to be given over x amount of hours i.e. 8 hours, then you divide it by this number which you have mentioned. You don't need to calculate any 2 x maint etc, but in reality as Carolyn has stated, you would take all factors in to account, i.e. dehydration status. The OSCE exam keeps it simple.

Re: fluid calculations

Steph Worsley — Sat, 11 Sep 2010 17:36:14 GMT

i find the easiest way to work out maintenance fluids is 2ml x kg this gives you the mls per hour

then multiply as required for twice maintenance etc

Re: fluid calculations

bongo — Sat, 11 Sep 2010 17:20:28 GMT

Maintenance requirements are 50 X bodyweight DIVIDED by 24 (you multiplied it) to get your mls/hr

Re: fluid calculations

Carolyn Edwards — Sat, 11 Sep 2010 08:51:28 GMT

Daily Maintenance (DM) = 50ml x bodyweight (kg)

Total Fluid Requirement (TFR) = DM x Maintenance Factor (ie: 2 for twice maintenance, etc) OR TFR = DM + calculated deficits based on dehydration factors, etc

ml per hour = TFR divided by 24 (if giving TFR over a shorter period you must be very careful that you don't overinfuse by exceeding maximum bolus rates)

ml per minute = ml per hour divided by 60

drops per minute = ml per minute x 20 (most giving sets deliver 1 ml per 20 drops, paediatric sets deliver 1ml in 60 drops)

seconds between drops = 60 divided by drops per minute