Dialysis pump speed question

[Panda_9]

The left side of my heart is slightly enlarged which is due to having such a high flow rate coming from the fistula. I am going to find out about pump speed before I say anything on that matter.

[Panda_9]

When everyone here talks about their dialysis machines pump speed, example: I run at pump speed of 400, what unit of measurement is this?

ml/min

If you've processed 100 liters of blood at the completion of a hemodialysis session, that's good.

If I run at 225 for 10hrs how much is processed. Im confused when you say 100L? It doesnt seem much. Or am I calculating wrong lol

[angieskidney]

Well I asked a different nurse at Dialysis yesterday and they absolutely refused to go above 350 on the machine. *sigh*

I couldn't go above 350 myself on Friday as my fistula kept spasming..

[Zach]

If I run at 225 for 10hrs how much is processed. Im confused when you say 100L? It doesnt seem much. Or am I calculating wrong lol

225 ml/min x 600 minutes= 135 L of blood processed.

1 L = 1000 ml

In my original post on the subject, I was using 100L as a goal, regardless of the pump speed.

[AlasdairUK]

The left side of my heart is slightly enlarged which is due to having such a high flow rate coming from the fistula. I am going to find out about pump speed before I say anything on that matter.

I found this description of the left ventricle on the internet:

The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.

The increase in size of your left ventricle is due to the extra fluid dialysis patients have between sessions. This is true for all HD and PD patients. The extra fluid increases the volume of your blood and your heart has to work harder to pump the blood. The extra work causes the left ventricle to increase in size. Pump speed does not have any effect on increasing the size of the heart.

Well I asked a different nurse at Dialysis yesterday and they absolutely refused to go above 350 on the machine. *sigh*

I couldn't go above 350 myself on Friday as my fistula kept spasming..

Your pump speed itself can be limited if your fistula flow is not sufficient as you are trying to pull too much blood out of the fistula compared to what is flowing in. It could have been down to the positioning of the needles on the day.

[angieskidney]

Well I asked a different nurse at Dialysis yesterday and they absolutely refused to go above 350 on the machine. *sigh*

I couldn't go above 350 myself on Friday as my fistula kept spasming..

Your pump speed itself can be limited if your fistula flow is not sufficient as you are trying to pull too much blood out of the fistula compared to what is flowing in. It could have been down to the positioning of the needles on the day.

I really think it might have been the position of the needle since when I have the access flow test done I can get a flow of up to 800+ml/hr through my fistula! 

I found this description of the left ventricle on the internet:

The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.

The increase in size of your left ventricle is due to the extra fluid dialysis patients have between sessions. This is true for all HD and PD patients. The extra fluid increases the volume of your blood and your heart has to work harder to pump the blood. The extra work causes the left ventricle to increase in size. Pump speed does not have any effect on increasing the size of the heart.

And AlasdairUK, thank you for your very informative post. What link did you get that from?

[sandman]

I found this description of the left ventricle on the internet:

The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.

The increase in size of your left ventricle is due to the extra fluid dialysis patients have between sessions. This is true for all HD and PD patients. The extra fluid increases the volume of your blood and your heart has to work harder to pump the blood. The extra work causes the left ventricle to increase in size. Pump speed does not have any effect on increasing the size of the heart.

That is very good to know.  Can you post a link to where you found this information?

[Panda_9]

If I run at 225 for 10hrs how much is processed. Im confused when you say 100L? It doesnt seem much. Or am I calculating wrong lol

225 ml/min x 600 minutes= 135 L of blood processed.

1 L = 1000 ml

In my original post on the subject, I was using 100L as a goal, regardless of the pump speed.

I get it now, I was just a bit confused

[AlasdairUK]

I found this description of the left ventricle on the internet:

The left ventricle is the largest and strongest chamber in your heart. The left ventricle's chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.

The increase in size of your left ventricle is due to the extra fluid dialysis patients have between sessions. This is true for all HD and PD patients. The extra fluid increases the volume of your blood and your heart has to work harder to pump the blood. The extra work causes the left ventricle to increase in size. Pump speed does not have any effect on increasing the size of the heart.

That is very good to know. Can you post a link to where you found this information?

Sorry, I only just read this now. I googled it at the time. I'm not sure what search string I used to find the description. I just tried again and could not find it.

[Bill Peckham]

I've been complaining lately about blood pump speed and the way the NxStage ties treatment length to pump speed and I thought for sure there would be articles supporting the idea that high pump speeds are bad in and of themselves - either by damaging the fistula or by enlarging the left ventricle. However, I could not find any articles - as has been written in this thread heart health is all about fluid management (another reason to go daily). Still the question of fistula health remained.

I asked Chris Blagg and Joe Eschbach both Nephrologists who were there in the early '60s when chronic dialysis was just starting. They said just what Bigsky has been saying - because the day to day flow through the fistula is - they said upwards of 600 ml/min, medical conservatism - that it was hard for them to think of a contraindication based on Blood Flow alone. Subject of course to overall fistula health. I still do not like the way the System One cycler ties blood flows to treatment length but high pump speeds do not in and of themselves cause a problem from what I can tell.

One issue that was discussed is how much blood would be lost if a needle dislodged with a Qb=450 v Qb=250 but that isn't really a clinical contraindication. And the idea was floated that a high pump speed may be more damaging to the individual blood cells but I think if that is a consideration that would only be a factor in mechanical roller pumps as opposed to the System One's bladder method.

[BigSky]

I've been complaining lately about blood pump speed and the way the NxStage ties treatment length to pump speed and I thought for sure there would be articles supporting the idea that high pump speeds are bad in and of themselves - either by damaging the fistula or by enlarging the left ventricle. However, I could not find any articles - as has been written in this thread heart health is all about fluid management (another reason to go daily). Still the question of fistula health remained.

I asked Chris Blagg and Joe Eschbach both Nephrologists who were there in the early '60s when chronic dialysis was just starting. They said just what Bigsky has been saying - because the day to day flow through the fistula is - they said upwards of 600 ml/min, medical conservatism - that it was hard for them to think of a contraindication based on Blood Flow alone. Subject of course to overall fistula health. I still do not like the way the System One cycler ties blood flows to treatment length but high pump speeds do not in and of themselves cause a problem from what I can tell.

One issue that was discussed is how much blood would be lost if a needle dislodged with a Qb=450 v Qb=250 but that isn't really a clinical contraindication. And the idea was floated that a high pump speed may be more damaging to the individual blood cells but I think if that is a consideration that would only be a factor in mechanical roller pumps as opposed to the System One's bladder method.

I do not know if this is true or not but I have heard that blood pumps speeds nearing the 600 and  higher range can cause blood cells to be crushed as they get pulled into and pushed out of the needles.

If that is the case I would think as long as one had a big enough needle and had the fistula to support the increased blood flow, one could run at much higher speeds than what we are allowed to run at now.

[Bill Peckham]

It would be interesting to see a study on fistula blood flow correlated to heart health. There may not be a correlation since the blood flow would grow over time and the heart may be able to accommodate a permanent increase in demand.

Is there an opportunity to design a high flow needle? One that would minimize cell damage.

[BigSky]

It would be interesting to see a study on fistula blood flow correlated to heart health. There may not be a correlation since the blood flow would grow over time and the heart may be able to accommodate a permanent increase in demand.

Is there an opportunity to design a high flow needle? One that would minimize cell damage.

I do not see a possible correlation myself as no matter what the pump speed is there is no more increased blood volume in the tubing or kidney.  But lacking a degree in science to study that stuff my opinion doesn't much matter to doctors.

It may well depend on what type of pressures the kidney and tubing can withstand and what type of back pressure may occur with higher speeds and that affect on the fistulas.

I do not see why I couldn't run a bigger needle than 15 gauge.   My fistula currently maxes out the equipment we use to test fistula flows and says its over 3000.

[renal30yrs]

I personally think 400cc per minute is the optimal number.

[Panda_9]

Straight from the horses mouth...

It's not so much the pump speed that is bad for the heart, but having
a fistula itself is bad for the heart.

Upper arm fistulas are running at 1 - 1.8L per min. Lower arm ones are
going at about 800ml per min. Grafts flow at speeds approaching 2L per
min I think. That sort of flow in a vein, which is a low flow/low
pressure system is not too good. It does put pressue on your heart,
which is already strained by the extra fluid you all carry about.

Pump speeds of 450mls/min can provide better CLEARANCE, but can leave
you feeling washed out. You would also need to increase the speed of
your dialysate flow to about twice the speed of the blood flow to get
the best out of it. For this pump speed, you would need a dialysate
flow of 800. We top out at 500, because increases above this doesn't
provide great improvements and you use so much more water.

To achieve pump speeds of 450+, you also need a fistula working at its
peak, or you run the risk of just recirculating. You would also need
to use 14G needles to reduce the pressure.

You only need these speeds when you are doing short runs. Nocturnal
goes the other way. Doing longer at slower pump speeds, with lower
pressures. We have the luxury of being able to do it long and slow.
Nocturnal also provides better clearance of molecules that are slow to
come off. The bigger molecules cause more long term harm.

[Bill Peckham]

Panda that conventional wisdom is what I use to hang my hat on but that was preNxStage. Before the NxStage came along we saw pump speeds toping out at 400 to 450 with many people (myself for one) opting to decrease Qb and increase my treatment length i.e. keeping total blood processed roughly the same but moving from Qb=450 to Qb=350 increasing my time from 4 hours to 4:45.

Now we have the NxStage and Qb determines ones treatment length directly, from treatment to treatment. If I now run at Qb=350 my run is about 4:30 hours with a Qb=450 my run is about 3:45 - so it is no wonder that we are now hearing about Qb=500 and higher! The biggest carrot available from the dialyzor's point of view is run length and the System One by connecting Qb and run length, incentivizes a high Qb.

I'm not sure what the marginal effect is of changing Qb from 350 to 450 or 450 to 550. What Bigsky and I have been trying to puzzle through is what exactly is the downside? More recirculation could be considered more of a needle placement issue. Perhaps one could say the a high pump speed makes the fistula larger therefore increasing the total flow which then increases the baseline stress to the heart. That seems pretty thin. I have changed my mind from agreeing with the previous conventional wisdon, I now think if the fistula is robust and needle placement does not invite recirculation that a high(er) Qb is ok. It feels strange to say but I think that is right.

[Zach]

I'm not sure what the marginal effect is of changing Qb from 350 to 450 or 450 to 550. What Bigsky and I have been trying to puzzle through is what exactly is the downside? More recirculation could be considered more of a needle placement issue. Perhaps one could say the a high pump speed makes the fistula larger therefore increasing the total flow which then increases the baseline stress to the heart. That seems pretty thin. I have changed my mind from agreeing with the previous conventional wisdon, I now think if the fistula is robust and needle placement does not invite recirculation that a high(er) Qb is ok. It feels strange to say but I think that is right.

What about the type of filter that NxStage uses?  Is it as good as the Fresenius F-80 or Optiflux-180 in removing the middle molecules? And what is the dialysate flow?  Panda is right about blood pump speed  ( Q_B ) vs. dialysate flow ( Q_D ).  How is a Lactate-based dialysate different than a Bicarb-based dialysate?  Not much info about these basic questions on their web site.     

[Bill Peckham]

I agree. I'd like to see a lot more information about the impact of Qd less than Qb. But I'm on it right now and at 30 liters it feels like good dialysis. I'm hungry when I wake up which I take as a leading indicator. My hemoglobin has declined - 11.8 from the 13s - I take a high natural hemoglobin as a sign of enough dialysis. I don't know if the NxStage cycler can deliver enough dialysis other than through nocturnal.

They call the System One a cycler for a reason. It uses lactate dialysate like PD and like PD the dose of dialysis is based on the amount of dialysate. They explain the NxStage works by increasing the "dwell time". By using slow dialysate speeds the dialysate spends more time along the membrane is the explanation. Basically the cycler gets the most dialysis out of a unit of dialysate. A Qd 2x Qb gets the most dialysis out of a unit of time.

My time is worth more than a unit of dialysate, I can't see the advantage of a cycler other than transportability. It seems to me the System Two should be able to switch between low Qd and high Qd, from a cycler to a hemodialysis machine.

[BigSky]

I'm not sure what the marginal effect is of changing Qb from 350 to 450 or 450 to 550. What Bigsky and I have been trying to puzzle through is what exactly is the downside? More recirculation could be considered more of a needle placement issue. Perhaps one could say the a high pump speed makes the fistula larger therefore increasing the total flow which then increases the baseline stress to the heart. That seems pretty thin. I have changed my mind from agreeing with the previous conventional wisdon, I now think if the fistula is robust and needle placement does not invite recirculation that a high(er) Qb is ok. It feels strange to say but I think that is right.

I do not think there is a downside if one has a good working fistula.  However the exception seems that many may not have the fistulas to support higher flows.  Kinda easier to do what works for most than to venture into uncharted ground for the view in this industry.  Also one thing might be as with the filter I use there is only a 10% greater urea removal between 400 and 500, my thinking is this might hold true for other filters also.  But hey lets get bigger and better filters to overcome this IMO.

[napala turki]

By simple calculation: example

Pump speed = 400 mi/min
so 1 hour = 400 x 60 = 24000 (24 litres)
so if 4 hours = 24 x 4 = 96 litres of blood out and returned.

An average our body has 4.7 litres of blood = 96 / 4/7 = 20.4
that mean the blood circulation has been process 20.4 times in 4 hrs.

I will try to create a table for a reference to everybody.... 

[napala turki]

As attached

[Bill Peckham]

By simple calculation: example

Pump speed = 400 mi/min
so 1 hour = 400 x 60 = 24000 (24 litres)
so if 4 hours = 24 x 4 = 96 litres of blood out and returned.

An average our body has 4.7 litres of blood = 96 / 4/7 = 20.4
that mean the blood circulation has been process 20.4 times in 4 hrs.

Dialysis cleans the fluid in the body. A person with 4.7 litters of blood would have over 30 liters of fluid. As a general rule for every liter of blood you have two liters of fluid between your cells and 4 liters in the cells.

Just quickly cleaning the blood - using a super efficient artificial kidney and a 600 blood pump speed - does not get you to where you want to be. You've only cleaned one seventh of the fluid in the body. You need time for the fluid and waste to transport between the compartments.

There is no substitute for time. The majority of the fluid is in the cells - four sevenths of the fluid you need to cleanse. But you only have access to the blood which is two semipermeable membranes away from the cell's liquidy cytoplasm.  The dynamics of the body's three fluid chambers are a bitch.

[Lucinda]

In Australia they don't encourage us to have a pump speed over 300.  Richard's clinic is pretty generous at 350.  I still have good residual function so I only do three hours every second day on a 280 pump and I don't need to take off fluid.  A lot of people say I shouldn't bother doing it at all but I have a lot of potassium buildup issues so it is enough time to lower my potassium.  We are also heavily encouraged over here not to take off more than two litres per session.  Four litres sounds like and awful lot to be dragging off in one session.

I have always been told to keep the pump speed down and take off as little fluid as possible to keep the heart healthy and put as little strain on it as possible.

[KICKSTART]

Hmm im finding all this very interesting and learning as i go ! Lucinda you regime sounds very similar to what we do as a standard practice over here , except for the time. I do fours hours , 3 times a week , with a pump speed of 300 and even though im overloaded have to fight to get them to take off more than 2l. (they will do it when im gasping for air tho !)

[Hanify]

I asked yesterday about this to my renal nurse to get a NZ perspective.  We're similar to Australia, but we also insist of 5 hour shifts because we believe it's better dialysis.  They would like to do every second day as well, but there's not the funding for it, so there's always that couple of days off each week.  If you do haemo at home you do every second day, but, for example, we're not able to do what Aleta and Del do - 5 nights on, two off, cos it's not funded that way.  I guess you might be able to if you were prepared to pay the difference.