Re: OSCE Fluid therapy task

Phrin Vernon RVN — Sat, 05 Nov 2011 22:40:12 GMT

I find it easier to do it like this - Say you have to work out drops per min for a 20 kg dog.

So maint = 50ml/kg/24hrs x BW

= 50ml x 20 kg

= 1000mls/24hrs

Divide by 24 to get mls /hr, so

1000mls / 24hrs = 41.67 mls/hr

Divide this again by 60 to give you mls per minute, so

41.67mls/hr / 60mins = 0.69 mls / min

Now you need to factor in which type of giving set you are using - most are 20 drops/ml (the ones they use in pracs are 20drops /ml)

So, 0.69 mls/min x 20 drops/ml = 13.89 drops/min, round up to 14 dpm

You don't need to go any further than that in your OSCEs You do need to remember all the units though

What I do in practice at this point is divide the dpm by 2, giving the no of drops required every 30 secs, and then sit and count, twiddle the dial, count again and so on until it is correct!

This is the way I was originally taught, and so the seconds/drop thing has always confused me lol

I can however do the dpm calculation in my sleep, and it got me through my OSCEs just fine :)

Re: OSCE Fluid therapy task

thebeestingbutterfly — Fri, 04 Nov 2011 23:13:41 GMT

I always used to get confused with fluid calculations, the way I was taught never stuck in my head, until someone showed me a different way of working it out (see the following example)

The basic principle is to:

1. Calculate the total fluid requirement for your patient.

2. Calculate the total fluid you aim to out in over 1 hour (so divide the total fluid requirement by lets say 24 hours for ease of use)

3. This answer tells you how much fluid you will administer over the hour.

4. Divide this again by 60 (as there are 60 seconds in a minute)- giving the total amount of fluid you wish to infuse over a minute.

This is the tricky bit!

Remember the answer you got in stage 4.

5. Switch the sum- you are now going to divide your 60 seconds by the answer( ml) you got in stage 4

6. The answer you now have is seconds NOT mls- this is where it gets confusing!!!!- remember we switched the sum so now our answer has changed.

7. Now we have to put our drip factor in! By dividing the answer (seconds) by our drip factor we get our answer! The answer being seconds between drips! – Clear as mud right??

I work things out differently to this method, you might find this easier: see the second calculation!

Example: 20 kg dog needs maintenance fluids over 24 hours, using a 20 drop giving set.

20kgx50ml=1000mls

1000mls/24hours= 41.66mls per hr

41.66mls / 60mins= 0.69mls per min

60 seconds / 0.69mls = 86.95 seconds

86.95 seconds / 20 (giving set factor)= 4.3 seconds between drips

20kg x 50ml= 1000mls

1000mls x 20 drop set= 20000 drops to go in over 24 hours.

20000 drops / 24= 833.33 drops to go in over 1 hour

833.33 drops/ 60 seconds= 13.88 drops to go in over 1 minute.

60 seconds / 13.88drops = 4.3 seconds

1 drop every 4.3 seconds

I hope this helps and hasn’t confused the matter more!!?? xx