How does KT/V get calc'd 6x's per week ?

[Don]

Does anyone know how kt/v is figured on 6x txs with NxStage?

Don

[Don]

 

I found a site that will calc it for you -

http://www.hdcn.com/calcf/ley.htm

Don

[Sluff]

I found a site that will calc it for you -

http://www.hdcn.com/calcf/ley.htm

Don

Thanks for the link Don. 

[Black]

I checked that site and did not see anything about the NxStage.

[jbeany]

The formula is in the nxstage manual, in the section labeled Appendix B, Conversion Tables and Formulas.  It is NOT explained at all, only the formula they want you to use is given.

[Black]

Thanks, beany -- will look for that tonight while Mike is on.

Just looked at it.  Daugirdas formula?  Anyone know what these letters stand for or how to do this?

spKt/V = Ln (R-0.008*t) + (4-3.5*R) * UF/W  (* means multiplication) so it could be written as

spKt/V = Ln (R-0.008 x t) + (4-3.5 x R) x UF/W

[jbeany]

Who'd a thunk I'd ever actually use my algebra class. . .
I'm guessing here on some of this - some of it is in the book, but not all.
Ln - has got to be length - how many days a week - so 5 or 6
R is your post BUN divided by your pre-BUN
t is time in minutes
UF is how much fluid removed during the session
W is post dialysis weight.

My nurse asked me to send her the following for the day I take the pre and post bun labs -
: date, length of tx time in minutes, #days per week, FF, dialysate volume, post wt and UF volume (goal)..

I'm not sure what formula she's using that needs to know the fluid fraction . . .

If I remember correctly from high school - do all the math in parenthesis first, then work right to left with the rest.

[Bill Peckham]

I like algerbra.
Ln (R-0.008 x t) + (4-3.5 x R) x UF/W
first solve the stuff over W starting with inside the parentheses. then multiply Ln by the first parentheses, then add the second parentheses, then multiply by UF. Finally divide by W. I think if it was written (4-3.5 x R) UF then you'd multiply UF and the second parentheses before adding. But don't worry about it because it's all a hoax.

It is measuring the easiest to remove molecule - urea - which also happens to be non-toxic. Urea is besides the point, so why focus on it? The question is how does the person feel? And if you increase the dose of dialysis by changing this piece of the prescription or that piece what is the impact? It'd be nice if we had a meaningful number (I think average blood cell life span in hours would be ideal) but we don't. All we can do is listen to the person on dialysis.

[Black]

... But don't worry about it because it's all a hoax.
... All we can do is listen to the person on dialysis.

I agree with you but the clinic is trying to use Mikes declining Kt/V as a reason to get an arteriogram on his fistula.  They say it can't be the computations of the Kt/V because they are using the computer software NxStage recommended.  Mike says he feels fine and doesn't want to do anything different, and will refuse anything being done to his fistula, except a Doppler ultrasound.  He says running at 500 blood speed with no alarms is sufficient proof to him that his fistula is not the problem with the Kt/V.

He's around 270 pounds, running 3 hours, 25L of dialysate, processing 88 to 90 L of blood.  With residual kidney function he doesn't have to remove much fluid -- went for 1.2 a few nights ago (which includes the .3 prime and rinseback saline) and he had cramping, so we backed off at .8.  I think we should try more dialysate and/or longer time.

We're new at this, so how important is the decline over several months from 2.2 to 1.8?   Actually, as discussed in another thread, the scale may be partly responsible.  Sometimes he has to weigh 5 times to get the same weight twice.  And, he usually snacks and drinks while on the machine, which could affect his ending weight, and also possibly the difference between his pre and post BUN.  Maybe the night he is doing the blood draw he shouldn't eat or drink anything during dialysis?  But if he eats shortly before starting dialysis wouldn't that have a similar effect?  Will he have to dialyse in the morning on an empty stomach to get a good Kt/V?  Or does food and fluid intake not affect the Kt/V?  As I said, we're new at this so we need the opinions of those more experienced.

The only time he has felt bad is when he was anemic a few months ago, so maybe we should ignore the lower Kt/V?

[Black]

After doing some more reading I have come to the conclusion that the Kt/V should be pretty much ignored as long as Mike feels well.  (Thanks to Bill Peckham for the comments which led me to do some more reading.)  At 270 pounds Mike was initially expected to have to do close to 4 hours but started at a shorter time because 20 to 40 pounds of that 270 is his PKD kidneys.  We both wish he could take off some weight, but we all know how hard that is to do.

But, since the clinic staff and the neph will be looking at the Kt/V and expecting it to go up, so can anyone answer the questions about food/eating/diet on the previous post?  Or is there anything else we can do to change the numbers?

[Bill Peckham]

I think the consensus is that what one eats during dialysis does not show up in the blood stream unless we're talking about nocturnal runs, then it's a maybe. In Europe in the 90's I would sometimes be given orange juice or a banana right at the start of the run - their thinking was that the potassium would be available to dialyze out during treatment. I heard that this approach was quite common in the early days of dialysis but you don't hear this much anymore. Generally I think it is recognized that the digestive process takes longer than a normal treatment. For a banana to be broken down/processed into a potassium molecule that is available to be removed by dialysis takes more like a day than a hour. Salt may be an exception to this - you might be able to eat those chips during treatment and have the sodium available for removal but salt has other problems - causes fluid to be harder to remove from between the cells.

Urea is even further along in the body's use of nutrition. Urea results from the breakdown of large molecules (think proteins) to smaller molecules (think amino acids). So my answer to your question: does eating during lab day impact the labs? is no. The more likely reason for a decline is a decrease in native output/native kidney efficiency or an increase in overall appetite and physical activity. Have you ever tried 30L for a couple days to see if Mike feels a difference? Feeling fine is fine but feeling great is great.

[JerseyGirl]

Has anyone done a recirculation calculation on his fistula?  At 500cc/min there could be a fair amount of recirc - meaning the same blood is being dialyzed because of the speed of the flow.  Recirculation calculations can be done by drawing a peripheral, arterial and venous blood value in the first ten minutes of tx and placing the results into a formula - I have the formula in my desk at work.  I think 500cc/min is too fast, and a fair degree of recirc may be occurring here.

[Black]

Has anyone done a recirculation calculation on his fistula?...

No, that hasn't been mentioned.

... Recirculation calculations can be done by drawing a peripheral, arterial and venous blood value in the first ten minutes of tx and placing the results into a formula ...

I assume the arterial and venous are drawn from the cannulation sets, but from where is the peripheral drawn?

... I think 500cc/min is too fast, and a fair degree of recirc may be occurring here.

According to our original training nurse most NxStagers use a blood flow of between 450 and 650.  Due to Mike's weight, we stopped increasing at 500.  Recirculation was not mentioned as being a problem at that speed but since you mentioned it I will contact the home dialysis nurse by e-mail now to ask her about that. 

JG, really appreciate your input.

[JerseyGirl]

The peripheral is drawn from a vein - the non fistula arm.  You draw them simultaneously within the first ten minutes.  It's a two person draw.  If they can't find the calculation I'll look it up for you next week.

[Black]

Thanks, Bill.  Being new at this it is very nice to have benefit of your knowledge and experience.  He will be soooo grateful to know that his snacking during dialysis is probably not responsible for the lower Kt/V.  He tries to watch what he eats and by snacking often he tends to not get so hungry that he over eats.

He is more active and is eating better than he was in Jan before he started dialysis.  He had reached the point where there were few foods that "tasted right" and he was not eating anything near a balanced diet.  His diet now is MUCH better.

I like the idea of trying 30L.  We have considered that before and it makes the most sense to try the easy things first.

Thanks again, Bill.

[Black]

The peripheral is drawn from a vein - the non fistula arm.  You draw them simultaneously within the first ten minutes.  It's a two person draw.  If they can't find the calculation I'll look it up for you next week.

Thanks, JG.  I'm pretty certain that someone at the clinic would know how to calculate that but if they don't I may be back in touch with you.  Actually, I wonder how we will do this since he does dialysis here at home and the clinic is 200 miles away.  I've never drawn blood from a normal vein and I'm not sure I could do it (or if he would even let me try    ).  Maybe we can schedule dialysis in the clinic one day and they could do it then.  If the Kt/V continues to be a problem this will definitely be done.  Thanks again for the input.

[Bill Peckham]

When I've had recircs done they've always used my arterial and venous cannulation sites as they would be during a normal treatment - the idea being that they are testing what is happening day to day. It's been a while since I've had them done - 5 or 6 years - but as I recall we did them when I came into the center to get iron. Rather than just getting iron I did a run too. You can be on any of the machines (the standard incenter machine, for instance) because they are testing the fluid dynamics of your access at a given pump speed.

If the needle tips are two or more inches apart there shouldn't be much recirc unless there is a narrowing downstream in the access. I've gone back and forth on Qb - choosing to run longer incenter back in the day so I could lower Qb to 350. With the System One a high Qb is greatly incentivized since it reduces treatment length/increases Qd and we now hear about Qb up to 500 (the System One can not go faster than Qb 500). There is not much data on cardiac impact of high Qb - I've looked (Dori just posted one article at HDC which I skimmed but it didn't look to be conclusive).

I talked to some of the Seattle neph doc luminaries at a social function a while back  - a little renal cocktail talk - and their thinking was that the native flow of a fistula was likely in the 800 range in a healthy fistula so no one could come up with a dynamic where a high Qb would impact much. One possibility that was mentioned was that a high Qb could lead to a larger fistula which could then have a cardiac impact but that was smart people thinking out loud not a proper study. I now try to run at 450; if I do end up doing nocturnal on the weekends come December I'll slow Qb way down but for System One logistic reasons not cardiac health reasons.

[JerseyGirl]

Yes you do get the value from arterial/venous samples but you need a true peripheral stick to compare for the results to be accurate.  The goal is 15% or less recirc.  If it is >15% it would be an indication for intervention.  Snacking on dialysis should not be a problem for KT/v calc either, so as long as his blood pressure doesn't drop go for it - just not too big of a meal just in case.  And no you wouldn't be expected to draw the peripheral on your own Ms.Black, and I had no idea your clinic was so far away!  Yikes!  I still think 500 Qb should be the max, and yes a good working fistula should have a flow of 800cc/ minute on testing.  Now there are studies coming out that a high Qb could lead to left ventricular overload cardiac wise. While I know there is alot of new data coming out, I am thankful for all these studies as in the old days we didn't have any!  Goes to show us that thankfully dialysis research has come a long way.

[kruep]

Hey guys,
If someone wants me to email them the spread sheet that I was given from NxStage to do all of my calculations for the clinic I can.   I saved it on a disc for just such things.  It has all of the formulas imbedded in it so all you have to do is plug in numbers. 

If someone can tell me how to put it on the web site I will be happy to do it so it will be available for all of you.

kruep