Do You Know Your Ultrafiltration Rate (UFR)?

John, I was discussing what I believe may be the most important dialysis lobbying issue with Rich Berkowitz earlier today. I recommended that they lobby congress/CMS to add UFR to the monthly dialysis reports since it has much better correlation to mortality than Kt/V. Rich felt it would be good to include in the QIP and decided to place a UFR calculator on his website.

It is probably a long shot to get congress or CMS to do such a thing unless there is already a demand for this information at the patient levels. I sent a copy to Chris Blagg and recommended that as a topic for the next ADC.


By Peter Laird, MD

Dialysis patients know their monthly hemoglobin levels, albumen, phosphorus, potassium and Kt/V but today, ultrafiltration rates are not published for the patients to review and understand. Sadly, excessive ultrafiltration rates are one of the major sources of morbidity and mortality for dialysis patients, yet CMS does not require dialysis units to report these figures to patients. Many recent studies articulate the risks of taking off too much fluid too rapidly leading to myocardial ischemia and stunning.

Fluid Removal During Dialysis and Cardiovascular Mortality: Results

Associations between UFR and All-cause and CV Mortality

Overall, 871 deaths occurred during 5,233 patient-years of at-risk time; 343 of these deaths were due to CV causes. The median survival time was 2.5 years. Compared with UFR ≤10 ml/h/kg, UFR >13 ml/h/kg was significantly associated with all-cause mortality: unadjusted hazard ratio (HR) (95% confidence interval (CI)) 1.20 (1.03–1.41) (Figure 1). When multivariable adjustment was used to account for baseline differences between groups, this association was greatly potentiated: HR (95% CI) 1.59 (1.29–1.96). UFR 10–13 ml/h/kg bore an intermediate association with CV mortality that was not statistically significant: adjusted HR (95% CI) 1.06 (0.87–1.28). Results were similar when UFRs following the long interdialytic break were excluded from consideration, when the referent group was restricted to participants with UFR 8–10 ml/h/kg (data not shown), and when flux and Kt/V treatment group assignments were included as covariates in the statistical model (Supplementary Table SA online).

The effect on mortality of ultrafiltration rates increase dramatically once it is above 10 ml/hour/kg. The calculation is quite easy to do. Using an example of a dialysis patient who weighs 70 kg, dialysis for 4 hours and takes off 2 liters of fluid, we have: 2000 ml/4hr/70 kg = 7.14 ml/hr/kg. However, if we look at a 70 kg patient who dialysis for 3 hours taking off 3 L of fluid, the calculation changes drastically: 3000 ml/3hr/70 kg = 14.3 ml/hr/kg. Shortening the dialysis time and increasing the amount of fluid taken off with ultrafiltration now places the patient in a higher risk of cardiac and all cause mortality.

Secondary Analysis

In order to more fully examine the threshold(s) at which UFR may become harmful, we
conducted analyses in which we examined the association of UFR, represented as a cubic spline, with CV and all-cause mortality. As demonstrated in Figure 3, the HRs for both CV and all-cause mortality rose sharply at values between 10 and 14 ml/h/kg, and to a less pronounced degree at higher values. Consistent with results of the primary analysis, the HR for CV mortality was greater than that for all-cause mortality at all values of UFR.

Just as all dialysis patients receive a monthly report showing URR, Kt/V, Alb, Potassium, Phosphorus and Hemoglobin levels, I believe that the UFR should be a monthly reported matrix as well that should also be tied into the QIP measures. After all, having normal labs and an “adequate” Kt/V and normal URR are meaningless if the patient undergoes concurrent dialysis sessions with excessive ultrafiltration rates that patients can easily calculate for themselves in the comfort of their own homes.

UFR and CV and All Cause Mortality ADjusted Hazard Ratio Calculator

Research has proven there is a definite relationship between how much fluid is removed per hour per kilogram of weight. This simple calculation will allow you to easily see how you compare to the Adjusted Hazard Ratio per the graph below. You can link to the specific Kidney International research paper HERE.

If your ultrafiltration rates exceed 10 ml/hr/kg, then please discuss these issues with your medical team on how you can avoid excessive risk of cardiovascular and all cause mortality. In addition, if you have an excessively high untrafiltration rate, you are most likely also at risk of feeling nauseous, vomiting, experiencing severe leg cramps and at risk of passing out during dialysis. In addition, if your ultrafiltration rate is high, many nephrologists will place you on a “sodium modeling program” where they add salt to your cleansing fluids that most patients retain after dialysis leading to severe thirst and headaches. In many ways, excessive ultrafiltration rates not only increase your risk of death, they also add greatly to the burden of symptoms associated with dialysis.

There is a better way to do dialysis and it all starts with longer, slower and gentler dialysis regimens. Short, fast and violent dialysis sessions leave patients feeling drained and at increased risk of heart attacks, chronic damage to the heart and severe discomfort during dialysis. The simple answer is to reduce ultrafiltration rates so that they don’t exceed 10 ml/hr/kg. This simple calculation could save your life and make your dialysis sessions easier to tolerate.

Dear Peter

I couldn’t agree more! I think your post is hugely important … but, dare I say with pessimism, not enough will read it or give it thought!

And, while I can only hope that the CMS might listen, the problem might be that it is a ‘soft’ figure to verify.

But, it is well worth thinking about, as it would mean much more than any waffle about Kt/V.

Just to legitimize and credit the authours of this nice study, the graphs you have reproduced and the data and quotes in your post come from a paper in:-

Rapid fluid removal during dialysis is associated with cardiovascular morbidity and mortality. Jennifer E. Flythe, Stephen E. Kimmel, and Steven M. Brunelli. Kidney International 2011: 79(2): 250-257

It is a very, very nice paper. It is spot on … and I only wish we had written it!

It certainly vindicates and proves the point about what I and others have been saying - and saying - all these years … that what matters in good dialysis is volume control and time … and if time and volume management are right, solute clearance will follow.

The (wrong) emphasis has been all about solutes - and the wrong solutes(s) at that! - when what matters most during dialysis is the preservation of circulatory integrity and the maintenance of blood volume.

The rest will follow, as night does day, but only if dialysis membrane contact time is extended to minimize volume disturbance.

Incidentally, Saran et all from the DOPPS Study group showed a long time ago now that when looking at UFR across DOPPS countries, the following observations held … and here, I quote their abstract in full (the spacing into sentence paragraphs is mine) from their paper: Longer treatment time and slower ultrafiltration in hemodialysis: associations with reduced mortality in the DOPPS. Saran R, Bragg-Gresham JL, Levin NW et al: Kidney Int. 2006: 69(7):1222-8.

[I]Longer treatment time (TT) and slower ultra-filtration rate (UFR) are considered advantageous for hemodialysis (HD) patients.

The study included 22 000 HD patients from seven countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS).

Logistic regression was used to study predictors of TT>240 min and UFR>10 ml/h/kg body weight. Cox regression was used for survival analyses. Statistical adjustments were made for patient demographics, co-morbidities, dose of dialysis (Kt/V), and body size.

Europe and Japan had significantly longer (P<0.0001) average TT than the US (232 and 244 min vs 211 in DOPPS I; 235 and 240 min vs 221 in DOPPS II). Kt/V increased concomitantly with TT in all three regions with the largest absolute difference observed in Japan.

TT>240 min was independently associated with significantly lower relative risk (RR) of mortality (RR=0.81; P=0.0005).

Every 30 min longer on HD was associated with a 7% lower RR of mortality (RR=0.93; P<0.0001).

The RR reduction with longer TT was greatest in Japan.

A synergistic interaction occurred between Kt/V and TT (P=0.007) toward mortality reduction.

UFR>10 ml/h/kg was associated with higher odds of intra-dialytic hypotension (odds ratio=1.30; P=0.045) and a higher risk of mortality (RR=1.09; P=0.02).

Longer TT and higher Kt/V were independently as well as synergistically associated with lower mortality. Rapid UFR during HD was also associated with higher mortality risk.

These results warrant a randomized clinical trial of longer dialysis sessions in thrice-weekly HD.[/I]

To put this in simple English … ‘the longer the treatment time and the lower the UFR, the lower the relative risk of dying’.

I will bring up the inclusion of UFR as a ‘national’ marker with my ANZDATA colleagues here and see how we go.

I suspect here in America, the academic nephrology community, CMS and congress will ignore this issue, but patients can know and understand how easy this is to calculate and understand. The graph says it all. This truly is an issue where a picture is worth a thousand words.

Please let us know how that is accepted “down under.” Thanks for the response John as always. And yes, that is a study a whole lot of folks wish that they had done as well. Unfortunately, it has not received the attention it deserves.

UFR and CV and All Cause Mortality ADjusted Hazard Ratio Calculator can be found HERE on

An excellent service …

I will work to ‘adjust’ my ‘Good Dialysis Index’ to include this data-point. Thanks Richard. Well done.

As a point of maybe interest using the given UFR formulae I find that with a UFR of greater than 7 then I beginn to feel quite “rough” after dialysis and my Bp will begin to drop heading toward going flat.
I now dialyse at home but previously whilst “in-unit” staff would contradict my observation and insist that Bp even at 85/45 (my norm being abt 140/80) is quie aceptable; this despite I and others having difficulty in walking out the unit after treatment
If only staff would take note of patients instead of the attitude that patients are not knowledgeable and staff know best maybe we could acheive bettethan “adequate” dialysis

David … I absolutely agree!

But, the problem is a two-way one (a double-edged sword) … or indeed, it is even more complex, and is a 3-step process …

(1) not only do we NOT listen to our patients enough (or, dare I regret, at all) but then, when the clear answer and solution is to lengthen the dialysis treatment …

(2) you, the patient(s), must listen to us and accept our wisdom and advice of slower, lower, gentler UFRs … a concept that we, the dialysing team(s), must better learn about, properly understand (many/most do not) and recognize as the means to the end of ‘better dialysis’.

then …

(3) we must adjust our schedules and practices to accommodate longer treatment times to make you better than you (collectively) are.

The crux of the problem is … how to overcome the two competing forces: the ignorance of ‘us’, the dialysing team vs the resistance ofyou, the dialyzor, to accepting longer therapy times.

The answer, of course, to the latter, is home therapy - where time can be easily, comfortably lengthened.

The answer to the former … well, it just gives me a headache thinking about it - let alone trying to change ‘our’ ways.

Will ever the twain meet?

I hope so … but no-one should hold their breath!

For those who see the merits of the argument … demand home dialysis - for there, and only there can you do to and for yourself what your body tells you should - no, must - be done … but isn’t … in facility care.

Why else do you think I have a passion for advising home, home, home whenever and to whomever I can?

John - you are exactly right. I have had renal nurse tell me that they will not do as I request in changing m/c settings because no renal nurse should be told by a patient what to do and conversely as a fan of HHD when visiting a unit patients say “you look very well” and I reply that I now do about 3.5 hrs pd but gain personal time because I feel so much better. Then 90% of reaction is “Yes well I wouldn’t spend all that time on a dialysis m/c” So yes with such attitudes makes one despair - but non deparendum !

Thanks David … and stay the course

We, as doctors and nurses …

Can I speak for the nurses?

Well, perhaps not for my own - for they are wonderful … and they listen!

But, back to the central theme …

We, as doctors and nurses are trained to ‘care for’ … to think that we have all the healthcare answers, that we have (almost) some ‘special right’ to guide and prescribe … and to be listened to. You, the patient, should listen - and do …

I have come round to the view that we … I … shouldn’t subscribe to that view.

My patients still surprise me, teach me, grow me.

And I love it.

More strength to your questioning arm!

Unfortunately, my relationship with most dialysis nurses and techs is very much an adversarial one. Two days ago, I went in-center for an iron infusion which I don’t do very often. They won’t let us do our own iron at home in America. This is the second iron infusion I have had since January. In January, I ran at my usual 350 ml/min BFR, but felt terrible when the session was over. I discussed this with my nephrologist a short while back and he stated that they use ultra-pure dialysate in his unit.

With that in mind, I paid closer attention to what the techs did when they set me up this time. I truly have no dry weight since I still urinate up to 2 L a day depending on how much fluid I drink. For convenience and because hardly anyone in dialysis can grasp the simple concept that I still pee just like they do, I have set my dry weigth at 91.5 Kg. I usually weigh about 89 Kb at home, so I set a dry weight that they won’t drop me like a rock if I can’t yell at them myself.

I told the tech and the nurse, I STILL PEE. Don’t take off any more than 500 ml just to tell the machine something. After making that statement at least 4-5 times, after I got hooked up, I looked at the setting. They had it on 1200 ml, 300 ml/hour. I frankly YELLED At them to put it on 500 ml and DEMANDED that they COMPLY. One shook his head and muttered under his breath to me, but that is the MINIMUM UFR. By the way, my weight that day at the unit with all of my clothes and shoes on was 91.2,below my alledged “dry weight” yet these ***** still set me for a “minimum” UF of 1200 cc.

Some techs and nurses are still adhering to the urban legand that you can prevent backfiltration with UFRs minimum of 300 ml/hour. When the shift changed, the second RN came over to “educate” me about minimum UFRs and backfiltration. I instead informed her that you get backfiltration at all UFRs and the minimum levels of 300 ml/hour does not prevent backfiltration. I have read some opinions that you would need an UFR of 4500 to prevent that. In addition, since this Kaiser unit has ultra-pure dialysate, it is a moot issue anyway.

After three hours of dialysis and after drinking a full can of Sprite, I was getting VERY thirsty and having a severe headache. I called the nurse back and asked what the sodium was set at. The techs had left it at the default setting of 140 instead of what the doctor ordered at 138. My usual serum sodium is 136, so I did in fact get a large salt load in those three hours. My wife had 1 L of water and I drank about 700 ccs right then and turned the sodium down to 138. That did help my symptoms greatly quite quickly. They won’t let me confirm my own settings since I am “only” a patient.

After I came off, I drank a total of about 3 L of fluid including the 700 cc during dialysis which does not count the 450 cc in the soda and still had very dark and concentrated urine of very low volume. I didn’t pee off most of this excess fluid until last night and this morning.

My relationship with dialysis staff is ADVERSARIAL in every regard because of time after time after time of mistakes on their part and NOT listening to what is my usual prescription. I STILL PEE techs. Get it through your thick head. I STILL PEE. YOU don’t have to dry me out like a bone every time I do in-center dialysis.

My wife gets mad at me for speaking up and yelling at them, but at this point, I could really care less if I hurt their feelings.

Well, I better stop before I really get ticked off about the whole situation.

Do SPEAK up. Do Correct the techs when they are out of line. It is an entire profession out of control in America and I am sick and tired and fed up with that lack of professionalism.

I now know why I felt so absolutely horrid in January. It won’t happen again.

In general, it is protocols, and not nurses, that impose problems of inflexibilty.

I would hate to see this post change direction toward nurse-bashing. I really don’t think they are the problem.

I strongly believe that the vast majority of nurses … and here, except for one single unit which does use highly trained non-nurse technician staff, all facility-based dialysis is performed by nurses if the patient isn’t self-dialysing in the facility … and/or technicians (as you commonly use in the US) … all have their patients best interests at heart.

No, it isn’t the nurses at fault … it is the practices and protocols to which they are taught to dialyse that are more commonly the problem. There are ‘unit protocols’, or ‘guidelines that have become rigid rules’ … always my ‘beef’ about guideline documents which, in genesis, are meant to guide (hence ‘guideline’) but when put to practice, become set in stone a ‘rules’. But then, that’s a whole different story.

Who sets the practices and protocols? Who writes the ‘guidelines’ that then become ‘rules’? We do … us! … the nephrologists. We are the ones that can (and should) change things. Don’t shoot the messengers!

Lost in the smoke has been ‘individuality’.

Dialysis should be individualised. But, that’s hard to do within the confines of a set of guidelines that have become a set of rules. Patients do need different settings, different UFRs, different sodium settings, different dialysis fluid composition, longer (but also different) time settings for dialysis length, different kidneys (read dialysers) … individuality and personal settings - settings which for any one patient may also need variability according to day to day circumstance. You do this at home. It is why you do well. We don’t do it (or do it enough) in units - which has a lot to do with why patients in units do (relatively) badly.

But, Peter, please … don’t bash the nurses too much. It’s commonly not their fault. They are doing what they have been told or taught to do … its just that they have been told or taught inflexibility and incorrect protocols. Rigidity never works. Flexibility is the way forward. I once wrote a paper on exactly that - flexibility in dialysis - for Nephrology - a journal unknown and unread in the US but which is the official Journal of the Asia-Pacific region and which encompasses all the Asian and pan-Pacific nations … NB: their the ones that are doing well in the world right now!

Bash the system - yes! It has drifted to be, in the main, a bad system … and it needs individuality, in big dollops!

The nurses? … be kinder. Yes, I know that inflexibility breeds conflict - especially when confronted by an individual patient who understands that … but they are, in the end, doing what they have been told to do and what they have been taught is right. It is the telling and the teaching that needs to change. A good nurse will change if the system within which she/he works permits that change. Bash the system.

And … one windmill to tilt at is the (very) odd habit you have over there of not allowing patients at home to self-administer iron! To me … that’s very odd!

The issue is more than just inflexible protocols which are at times based on faulty assumptions such as the “minimum UFR” issue. But there is more John. I had Dr. Rasgon write specific orders for my dialysis so I wouldn’t have to be confrontational with the techs. These doctor orders included UFR total of 500 mls only and Sodium of 138. They ignored the doctors orders, they ignored my information telling them I still pee and cannot have more than just a little bit of Ultrafiltration essentially equal to the amount of saline used to prime and they further did not change the sodium. That is more than just adhering to rigid protocols. Dr. Rasgon does not have a rigid protocol for minimum UFR that I am aware of.

In addition, don’t get me started about their hand hygiene two days ago either. Dr. Rasgon has gone to extraordinary lengths to improve hand hygiene and it is my impression after three sessions in this unit that they give it lip service only.

Sorry John, but the dialysis industry and the techs and nurses need to clean up their act very much so. That is not nurse bashing, that is just a pure statement of facts. I have indeed not gone into the entire retaliation aspects of dialysis units either which is a major problem in American units that is hid under the rug so to speak. I have experienced that myself but will not go there at this time.

I agree with your point John, but my goodness, the entire industry needs to wake up and act in a professional manner across the board. That is not happening today.

No other medical specialty seems to know so little, yet pretend to know so much, all the while making such a huge amount of money on junk science. No John, it is not a matter of “making ourselves more aware”–it is finally being held accountable for deplorable behavior.