In nocturnal home programs some say they run at 300 and others say 250. In-center we are not allowed to turn the UF off when there is cramping. We can only put the machine into to minimum which is 300 for our unit. What are you trained to do should you experience cramping?

Give saline, pause UFR for 15-30min…then turn UFR back on…

We were told the UF can not be turned off as dialysate can get through the dialyzer. There is a term for it… anyone know what it is?

Weird, never heard that one before, but back when I was in-center that was done…pause UFR for a few minutes then back on and/or decrease UFR…

Perhaps maybe Backflushing? …

In-Center dialysate may not be the best dialysate as our dialysate at home higher quality and in some cases infuseable…so in the case of in-center dialysate(standard form) there’s more risk of getting reactions and infections…like those strange chills or unusual temperature rising…I had all those in-center, but now at home its all gone… :smiley:

I’ve had cramps on short daily, but I’ve never had a cramp on nocturnal. The UF rate is just too low for that, even if more than 3 kg over dry weight. You get cramps when water and salt and potassium are removed faster from the blood than they can be replaced by shifting from the extracellular spaces (where most of it actually is). The speed at which this shifting occurs is about 350-400 ml/hour (fluid). Since the UF rate on nocturnal is almost never higher than this, you don’t get cramping, since you’re not trying to pull the fluid from extracellular spaces faster than it can shift to your blood.

Now, it’s possible a person who isn’t paying attention to low pre and post blood pressures might gain real weight and eventually, get very dry because dry weight has become too low. I guess you might get cramps then, but I think low blood pressure would be your first sign.

The speeds you mention, like 300 vs 250, are blood pump speed, not UF rate. This is little to do with cramping.

On the odd chance that I do get cramping, I’m trained to lower pump speed to 200 and infuse saline for exactly 1 minute (with UF off during that time only). The lower blood pump speed is not for the cramping itself, but to prevent the chest discomfort you get if you infuse saline too quickly - it momentarily deprives the heart of blood (saline is there instead).

When it comes to blood pump speed, it’s not really that there’s a minimum but rather that you need enough blood pumped through the dialyzer to get enough dialysis from your treatment. With the longer nocturnal treatments, it can be slow like 250 and it stills provides all the dialysis a person needs. If you’re running short daily treatments or 3-4 hour conventional treatments, you are very unlikely to get adequate dialysis if you run much slower than 400 for any length of time.


The information sheet on Fresenius dialysers suggest not running at a rate of less than 300. The slower the rate the more back filtration occurs (dialysate flowing into the blood circuit). If you do a linear calculation you can show that the pressure on the blood side is higher than the dialysate side over the to 55% or so of the dialyser, but lower over the bottom 45% for typical nocturnal dialysis settings. “Real world” numbers might be a little different from linear, but back filtration is undoubtedly substantial. I haven’t been able to find out from anyone what the clinical consequences are, but they hopefully are negligible.


My instructions from day one have been to always ensure I end up with a UF rate of 300 ml/hour. I think that early on when I started participating in this group, some of us had discussions about running a slower UF rate. The recommendation for Fresenius dialyzers is to not go under 300 ml/h (UF rate, not blood pump speed). This is necessary for high flux dialyzers, because the membrane fibers are very porous and if you don’t have a high enough UF rate, the transmembrane pressure will be too low and you will have excess backflushing. Low flux dialyzers don’t have that requirement.

During the early years of daily nocturnal, they were concerned that patients might develop deficiencies, and so they ran a low blood pump speed (like 200-250). Over time, they found that no deficiencies occurred. This is why that nowadays, the blood pump prescription for daily nocturnal is usually 300 ml/min. The slower the speed, the less dialysis you get (since you will be pumping less blood through the dialyzer over the same period of time). So, there’s a practical limit. For that reason, unlike nocturnal, the short daily 2 hour treatments require a blood pump speed of 400 or more.

But for those of you who aren’t yet on home hemo, it’s important to get the numbers straight:

UF rate is the speed at which fluid is removed. It is measured in ml/hour.

Blood pump speed is how fast your blood is being pumped. That’s measured in ml/minute.

As far as the patient is concerned, there is no connection between UF rate and blood pump speed.


Pierre wrote:

If you’re running short daily treatments or 3-4 hour conventional treatments, you are very unlikely to get adequate dialysis if you run much slower than 400 for any length of time.

Years ago we read articles which stated that it is not recommended that fistulas be run at more than 350. We conferred with other seasoned patients as to their suggestions for blood pump speed and they agreed 350 is the limit (heart, longevity of access). We also asked about needle size and were told the smallest you can use and get good clearance. Using only 16 ga needles and 4hr txs incenter come out with a kt/v over 2 which is quite good. We found the dialyzer used also figures into the equation and the dfr. And setting up the tx properly including machine and needle placement is very important, because if the machine alarms a lot or needle is up against the wall and has to be readjusted, it definitely affects clearance. Nephs we have had didn’t believe it was possible to get good clearance with the bps and needle size we requested until they saw our labs. Everyone else is put on high speed dialysis. We have never had an access problem.

Measuring Local Ultrafiltration Rates in Hemodialysers using Magnetic Resonance Imaging

Email Corresponding Author (
Research Advances in Artificial Kidney Membranes session

Peter Hardy, University of Kentucky (Corresponding)(Presenting)
Churn Poh, University of Kentucky
Dayong Gao, University of Kentucky
William Clark, Baxter Health Care

Hemodialyzers or artificial kidneys are used to remove excess plasma water and uremic solutes from the blood of patients with renal failure. A typical hemodialyzer contains 10,000 to 12,000 semi-permeable, hollow fibers. The physical characteristics such as wall thickness, porosity and pore shape of the hollow-fiber’s membrane define the molecular cutoff of the uremic solutes to be removed. Small molecular-weight uremic solutes such as urea are removed by diffusion transport, and large molecular-weight uremic solutes such as beta-microglobulin and excess plasma water are removed by convective transport. The blood flows through the lumen side, and the dialysate solution flows counter-currently through the shell side of the hemodialyzer. Countercurrent flow maximizes the pressure across the hollow-fiber membrane and thus enhances the convective solute transport. Along the approximately 20 cm length of the hollow fibers, negative transmembrane pressure from the lumen side to the shell side of the hemodialyzer can occur in high-flux hemodialyzers, which leads to flow of fluid from the shell side to the lumen side, a phenomenon known as backfiltration. Backfiltration is potentially problematic as it could transport endotoxins into the patient’s blood stream resulting in infection. The net flow of fluid from the lumen side to the shell side of a hemodialyzer including any backfiltration is termed ultrafiltration. A typical high-flux hemodialyzer has an ultrafiltration coefficient between 50 to 80 ml/hr/mmHg. The goal of this research was to quantify local ultrafiltration rates along the length of clinical hemodialyzers.


There’s much more to it than kt/v.

Is BP normalized?

Is phosphorus normalized?

What about other things like microglobulins?

We already know that a good kt/v in conventional hemodialysis has proven to not mean much in terms of reducing morbidity and mortality. But even so, if you have to be on conventional hemo 3 times per week, I imagine you would want to maximize the benefits, no matter how you measure that. Larger bore needles weren’t needed once high-flux hemo came along. Everything has pros and cons. What’s worse for the fistula, being stuck with larger needles every other day, or, using smaller needles but running the pump at a slightly higher speed? These are questions which are virtually impossible to answer.


The word you’re looking for is backfiltration. It can happen when the tmp goes into the pluses, which could happen if the uf were turned off too long or the goal was set too low. This happened to me three times when I first started dialysis but staff wouldn’t admit it; they insisted I must be coming down with something, three txs in a row lol It doesn’t happen on the Fresenius machine I’m on now because even when my goal is set as low as 500 the machine still takes off more so I’m guessing here that there is some sort of internal setting to avoid positive tmps. I watch anyway! I’m wondering how it will be for me on the Nxstage machine. Lin.

Hi Lin

From my discussions with machine techs, the Fresenius machines have extremely precise control of ultrafiltration. They have to, because they have to be able to handle just about any type of dialyzer you can hang on them, dialyze children, etc. What I found myself when I did try to run with a low UF rate under 300 ml/hour was that I got a lot of fluctuations in TMP from high to low and back again - enough to trigger frequent TMP alarms during the night. It’s like it had trouble keeping a steady UF rate. At first, to be honest, I didn’t believe my nurse that I had to have a UF rate of at least 300, but then I saw that it says exactly that on the insert that comes in each box of my dialyzers.


I would have to agree that on some Fresenius and other brands of dialysis machine doesn’t cause backfiltration.

In my early years of dialysis there was no fresenius machines around but the one I used always always was getting me dry regardless whether UFR was used or not, several years later the Baxter 1500 was put in place…it was a dream machine…it had volumetric control! …and from there and beyound is where more chills or unusual temperatures occured…then finally in the later years they put place the Althin brand machine which I considered the worsest from previous machines I used…

…so I really think so, todays latest dialysis machines most likely already have control over preventing backfiltration.

NxStage System One is quite unique, never exerpienced any backfiltration at all…even with no UFR at all…perhps the low dialysate rates have something to do with it…

I experienced backfiltration on the Althin which was running + a lot. The Fresenius machines are better at handling things, but that is because they really can’t be set low. Whether they set the machine for 500 or up to 800 the tmps stay pretty steady albeit lower; always negative. However, once in awhile they will put me on a machine that isn’t calibrated as good and it will alarm even if the uf is higher. Keep in mind I don’t need any fluid removed so minimum for me is lower than for anyone else. We (husband’s suggestion when I first started dialysis) was that if we run on a low uf but keep the dfr high the tmp will stay in the good range for me. Most people will need at least some fluid removed so won’t have to worry; I suspect it would come up more for those on slow nocturnal who need little or no fluid removal. Even when the Fresenius machine I’m on is set for 500 (for 3 1/2 hrs) it still removes more fluid. The fever and chills are a whole other ballgame; having that plus diarrhea while on tx. is no picnic, and it goes away once done with tx… Friday they must’ve forgotten to run the extra saline through the dialyzer because I had horrible flu like symptoms after tx… I’m hoping that for a pt. like me the Nxstage will solve at least some of my problems. I think it would be good if centers who offer home hemo would be aware of machine capabilities and drawbacks, and pts. would be put on whatever one suited them better. Unless you’ve ever suffered from backfiltration you really don’t know it exists, and even then someone will always tell you it’s a cold or flu.
Found a really nice arm chair for my home hemo.; it goes all the way back, and is remote controlled and low voltage; even has battery backup in case the power fails I wouldn’t be stuck in my chair; HELP I’m in my chair and get get out lol Lin .

More info please – been keeping an eye out for a new chair for Hubby. He’s over 6 feet tall and over 250 pounds, so he needs a big one. Remote control sounds great!!

Here’s the link.

We went to our favorite local furniture store because we knew they had a few famous maker lines of chairs but the sales person asked what we were looking for and he showed us this chair (more choices in catalog) that I fell in love with. It was the only chair that went completely back and was low voltage with a lift seat. It’s my understanding that they aren’t sold directly but rather in furniture stores but don’t know for sure. Lin.

Make sure it’s stain proof. There’s bound to be some blood on it sometime :slight_smile:

Thanks, Lin. Will check further on these.

I think for these type of questions you really should be asking your HD unit. Each unit may have different protocols. If we are feeling like going flat, we are instructed to turn the UF off, check BP, and if needed, give saline. I try to avoid giving saline if I can. Its a bit hard if you are alone, but we are also intructed to lay flat. It makes it hard to mute the alarm though :?

We have been doing nocturnal going on 6 years. Rarely does dad ever have a UF rate of 300 he just can’t drink enough. I have never had a problem with TMP alarms or backfiltration. I don’t disagree it should be min of 300 but you can’t do what you can’t do and so far it hasn’t been a problem for us. I don’t think the machine is compensating either because if it were when we came off our weight would be way off. Our unit has never insisted we have a minimum UF of 300. All they ever said was be careful when its time to come off because when the time is up the machine will automatically reset the UF rate to 300 and you could take off alot more than you wanted if you mess around to long before you start to rinse back and get off.