# CRRT question

1. Our facility has just started using CRRT in the past couple of weeks. We are having a huge debate amongst each other about how to calculate the patients fluid balance. Our educators insist that we just take the total fluid removed off the prismaflex and then subtract any other losses or gifts (ie pleural tubes or boluses) and that is our balance.

However, everyone else is thinking that we have to subtract our intake from our fluid removed to get a true patient fluid balance.

So far with the existing calculation we are getting a fluid removal of around 3 to 8 Liters for every 12 hour period. This seems really excessive, but we are told that it is correct. How can this be correct when we are supposed to be taking off around 600mls of fluid per shift?

Can anyone share how their facility calculates the 24 hour fluid balance?

Thanks!
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3. you have to add all input.(iv fluids, parenteral feeding, blood products-whatever) Then subtract that from all out put (urine, ng, chest tubes etc). the answer is howmuch you actually took off or not
4. Same with regular I/O total in minus total out, iv fluids, tube feeds, etc, minus crrt minus ct, ng output, urine output if they're having any
5. Quote from gizdo
So far with the existing calculation we are getting a fluid removal of around 3 to 8 Liters for every 12 hour period. This seems really excessive, but we are told that it is correct. How can this be correct when we are supposed to be taking off around 600mls of fluid per shift?

Thanks!
The other posters made mention of adding up every drop of output and input, including it in your calculations and all of that, and i'm sure you're doing it. To me it sounds more like you're confused because the effluent bag (and thus your 'output') is filling up so rapidly...

From your question, it seems like you're measuring 3-8 liters of EFFLUENT every 12hrs (and NOT patient fluid removal). EFFLUENT is the amount of fluid removed from the patient PLUS the DIALYSATE (and/or replacement fluid) that's running into the crrt machine. (it all ends up in the effluent bag). The dialysate (and/or replacement fluid) never goes into the patient (and thus is not an INPUT), but because it drains into the effluent bag WITH the patient removal, many people assume the entire bag is an 'output'. If you were trained properly, you'll be able to see on the machine display what the actual fluid removed is/was per hour...and be able to manipulate it depending on the hourly circumstances... (should be about/around 600 cc/8hrs for this pt, right?). The effluent needs to be recorded...but it's not an ouput. IF your institution insits on you recording the dialysate and replacement fluids as input (which technically they arent), then your i&o's should be roughly correct if you're also considering the entire volume of the effluent bags as output.

Anyway...
IF i'm wrong and your ARE pulling 3-8 liters of actual patient removal in 12 hrs you will kill the patient eventually...or at least make an already unstable patient VERY unstable...fast. Or if you ARE pulling that volume off the patient and she/he is tolerating it (MASSIVE FLUID SHIFT/LOSS) , he/she does NOT NEED crrt...and should be on standard dialysis...and you need to STOP pulling so much so fast...
6. Quote from Dinith88
The effluent needs to be recorded...but it's not an ouput. IF your institution insits on you recording the dialysate and replacement fluids as input (which technically they arent), then your i&o's should be roughly correct if you're also considering the entire volume of the effluent bags as output.
I think Dinith is right-on with the math and explanation. These volumes aren't REALLY going into the pt or coming out of them. Make sure your net is correct.

I think most institutions should require all volumes on CRRT to be documented (dialysate, replacement, effluent). These are usually high volumes, and will show mathematical errors very easily, thank God! If you're performing CRRT yourself, you should understand the mechanism and how the fluid and solutes are shifting. You should be very involved with what the fluid goal of your shift should be, and making sure you're meeting the goal on an hourly basis. If your goal is to make your pt -1 liter on your shift, I sure hope your math doesn't show they're -6 liters!
7. Thank you, everything you guys have said is exactly what I was thinking too. I kept telling our educators that there is NO WAY we were taking off that much fluid in a 12 hour shift. Now I just have to convince them! Sheesh...it's just simple mathematics...I can't believe we are having this much trouble with this.

Thanks!
8. We also recently initiated CRRT at our institution and were not inserviced very extensively prior to starting it. My biggest debate with my co-workers is about how to calculate your next hours pt fluid removal rate. Here is a hypothetical, please let me know what each of you would program in as your next removal rate for the following previous hour:
Net Goal Removal 50cc/hr
Current Pt Fluid Removal Rate 100cc/hr
This hours total Intake 350cc
Non Prisma total Output 100cc
Actual pt fluid removed for this hour 150CC
What do you program the next hour Removal Rate as? Across the board in my unit we are calculating this quite differently and it's very frustrating.
9. Oh I should mention that our Trauma Surgeons have been initiating and ordering the prescribed rates for our CRRT patients as opposed to getting a nephrologist involved. Unfortuntalely several of them are "old school" and therefore not up to speed on this form of therapy and therefore we have many discrepencies in our orders day to day based on who is rounding.
10. I pulled this from the prismaflex site:

Q: How do I calculate fluid removal rate?A: The patient fluid removal rate is the net amount of fluid the PRISMA system removes from the patient each hour (after accounting for any replacement solution being used). Net fluid removal occurs whenever the operator sets the patient fluid removal rate to a value above zero.
Calculating the desired patient fluid removal rate:
The PRISMA Control Unit software does not measure or account for non-PRISMA sources of patient fluid intake (such as hyperalimentation, blood, or drug infusion) or fluid output (such as urine and wound drainage). It also does not account for anticoagulant solution infused via the PRISMA anticoagulant syringe pump. The operator must account for these other sources when calculating the patient fluid removal rate, as well as when calculating the patient's input/output totals. The following formula may be useful:
Non-PRISMA fluid input (ml/hr)
- Non-PRISMA fluid outputs (ml/hr)
+ Prescribed patient fluid loss (ml/hr)
---------------------------------------------------
= Patient fluid removal rate to be set on the PRISMA Control Unit (ml/hr)
The patient fluid removal rate must be adjusted if the weight loss prescribed by the physician is changed or if the patient's non-PRISMA fluid inputs or outputs change.
Machine Control of Patient Fluid Removal Rate:
The PRISMA software automatically calculates the ultrafiltration rate needed to achieve the patient fluid removal rate. Any PRISMA replacement solution additions are automatically accounted for. During operations, software controls the effluent pump speed to maintain the required ultrafiltration rate
11. Quote from gizdo
Our facility has just started using CRRT in the past couple of weeks. We are having a huge debate amongst each other about how to calculate the patients fluid balance. Our educators insist that we just take the total fluid removed off the prismaflex and then subtract any other losses or gifts (ie pleural tubes or boluses) and that is our balance.

However, everyone else is thinking that we have to subtract our intake from our fluid removed to get a true patient fluid balance.

So far with the existing calculation we are getting a fluid removal of around 3 to 8 Liters for every 12 hour period. This seems really excessive, but we are told that it is correct. How can this be correct when we are supposed to be taking off around 600mls of fluid per shift?

Can anyone share how their facility calculates the 24 hour fluid balance?

Thanks!
Your post is really confusing---I won't even start with what I can't figure out from what was posted so I'll tell you what we do.

Here is a summary of our calculation form:

Line one: Desired patient fluid removal rate (for example, 50 ml/hr---this is the prescribed desired loss from the orders)
Line two: Difference between previous hour's total desired removal rate and actual fluid removed that hour (plus or minus)---this is added or subtracted to or from line one (see below to help make this easier to understand)
Line three: total NON-PRISMA fluid intake from the previous hour---IVF, PO fluids, tube feeding, blood products UNLESS there is an order not to include blood products (or fluid boluses) in CRRT calculations. Total is added to the above number.
Line four: Total NON-PRISMA output: drains, U/O, etc. This is subtracted from the above number.

The number you get after calculating the above is the number you put into the Prisma as your hourly removal rate.

At the end of the hour you get your "actual fluid removed" number from the machine and subtract it from the number you put in as your hourly removal rate. This plus or minus number is carried over to the next hour's "line two" and factored into the next hour's calculations.

The "actual fluid removed" number is ultrafiltrate and counted as output. The big effluent bag is just dumped and is never counted as anything except contributing towards a massive backache after a few twelve hour shifts of Prisma.

The ultrafiltrate is counted as a separate output on our I&O fluid balance sheets. It is factored in along with U/O and any other measured drainage when calculating total output. Intake is what it always has been---IVF, PO intake, blood products, etc. Dialysate and Prisma replacement fluid are never counted as intake just as effluent is never counted as output.

Fluid balance is calculated as it always has been too---the only difference is the addition of the Prisma ultrafiltrate as one of the categories of output.
12. Quote from Go UT Vols
We also recently initiated CRRT at our institution and were not inserviced very extensively prior to starting it. My biggest debate with my co-workers is about how to calculate your next hours pt fluid removal rate. Here is a hypothetical, please let me know what each of you would program in as your next removal rate for the following previous hour:
Net Goal Removal 50cc/hr
Current Pt Fluid Removal Rate 100cc/hr
This hours total Intake 350cc
Non Prisma total Output 100cc
Actual pt fluid removed for this hour 150CC
What do you program the next hour Removal Rate as? Across the board in my unit we are calculating this quite differently and it's very frustrating.
Okay. I can't believe you guys are not using a standardized calculation formula. Are you just winging it??

You want a net output of 50cc from the patient each hour.
You take that, add the total intake. We are up to 400 cc here.
Your non-Prisma output is 100 cc. You subtract that from the 400cc and now we are at 300.
The Prisma fluid removal rate was set for 100cc/hr but took off 150cc---so you are negative 50cc for that hour. In order to achieve balance you must factor that into your next hour's calculations so you subtract the 50cc from the number 300 that we arrived at above.
And that's the number you put in for your next hour's removal rate---250.
13. Quote from Summitk2
I think Dinith is right-on with the math and explanation. These volumes aren't REALLY going into the pt or coming out of them. Make sure your net is correct.

I think most institutions should require all volumes on CRRT to be documented (dialysate, replacement, effluent). These are usually high volumes, and will show mathematical errors very easily, thank God! !
Why would you document those fluid volumes on an hourly basis? To me that just seems like non-functional information clutter.
In all the years that I've done CRRT, always in teaching hospitals, I've never had to document the volume totals of dialysate, replacement, or effluent. Yes, the hourly rates of dialysate and replacement fluids are MD orders and plugged into the PRISMA touch screen but we do not "document" them on an hourly basis. They are usually the same for the entire course of treatment and are not factored into the equations for hourly operation. As you stated, the dialysate and replacement fluids are not patient intake and the effluent is not considered patient output.
If they are being documented as such I shudder to think what the daily I&O totals would be.
We do document filter, access, return and effluent pressures, and TMP. Also Prismatherm temp
What "math errors" would show up by documenting dialysate, replacement and efflluent volumes? I'm confused.
14. Thanks everyone for your input. Just to clarify we do not record hourly set prisma volumes (i.e. replacement, dialysate, etc.). But unfortunately we also do not have a standardized formula for calculating hourly fluid removal rates. I think most of the concern is that many people do not believe you need to take into account your current removal rate to calculate the next hours rate (at the top of the hour), while others, like myself, think it has to be a factor in your calculations in order to obtain a cumulative shift targetted removal rate. Unfortunately we are still the blind leading the blind and our physicians are Trauma Surgeons not Nephrologist when this therapy is implemented which adds to the confusion (seems wiser to consult an expert in the field but that's a whole other thread!!)