A Rational Approach to Dialysis Time and Frequency
Good dialysis depends on the combination of both:
- Optimal frequency: to permit small and large solute removal.
- Optimal time: to allow slow, perfusion-friendly rate of volume removal.
The current Kt/Vurea formula has unfortunately encouraged clinicians to increase one of the two numerator variables (K) in an effort to reduce the other (t). This has resulted in the human body being treated like a multiplication table, where increasing one variable and reducing the other yields an unaltered result. Both 2 x 4 and 4 x 2 = 8.
Short hours, low frequency dialysis
This is the current majority reference point for most dialysis patients, and is how current “conventional” dialysis can best be described. Even conventional dialysis—as the term is loosely used in the dialysis literature—is not a single entity:
- In the US, it is commonly 3.0 - 3.5 hours, 3 times a week.
- In Japan and ANZ, it is more commonly 4.5 - 5.0 hours, 3 times a week.
These are unlikely to be fully comparable, either in the efficiency of solute removal, or in the speed of ultrafiltration. Yet, they are frequently conflated and compared as if they were the same in open discussion or in literature reports. Conventional centre-base dialysis – and especially the US conventional model – offers neither sufficient time for full solute removal, nor sufficient frequency for volume control. While an inadequate sessional duration “seduces us” by providing an apparently adequate cleansing of small solutes like urea, the more insidious middle molecules that depend on time for removal are not sufficiently removed.
Further, the rapid ultrafiltration rates required to remove the accumulated interdialytic volume excess are known to promote intradialytic circulatory instability and hypotension, cramp, nausea, vomiting and—more threateningly to survival—“stunning” of vital organs, in particular the heart and brain. Yet, to our shame, this dialysis model is the option most current dialysis patients are offered, and receive.
Long Hours, Low Frequency Dialysis
This is exemplified by most current in-centre nocturnal dialysis regimens. Longer duration dialysis, especially those regimens (commonly nocturnal) that permit between 7 and 9 hours of sessional duration, encourage deep-compartment cleaning (Eloot). Intercompartmental and transcompartmental “deep cleaning” of time-dependent solutes takes exactly that: time, and time cannot be artificially accelerated. So, while from a solute perspective this model works, its failure lies with poor volume management, as the result of inadequate frequency.
A longer interdialytic period will inevitably bias towards a larger interdialytic fluid gain. The more hours without dialysis, the greater the time a patient has to eat, drink, and accumulate excess fluid volume, albeit patients who retain the benefit of a residual urine volume will be at greater advantage under this modality than those who are anuric. Thus, while in theory the longer sessional duration of this model should permit a slower ultrafiltration rate, this theoretical benefit may be effectively cancelled out by the larger accumulated interdialytic volume that requires removal.
High(er) Frequency, Shorter Hours Dialysis
This modality is typified by the (largely US-centric) “short daily hemodialysis” (SDHD) model. Current SDHD broadly favours an increase in treatment frequency to 5 or 6 treatments per week. But, as this model concurrently trades-off a reduction in sessional duration against an increase in frequency, it still does not provide the wisest or most appropriate answer.
- Re solute removal:
- Higher frequency dialysis benefits small solute clearance by more frequently providing a maximal concentration gradient for small solute clearance.
- But…most so-called “middle molecules,” (or PO4 with its hydrophilic skin) are characterised by linear diffusion over time and, rather than moving down a concentration gradient (like urea), exhibit time-dependent removal patterns.
- Thus, while high frequency combined with time-reduced dialysis may deliver better small solute clearance (as measured by Kt/Vurea), high frequency combined with truncated time does not significantly improve larger solute clearance (e.g. β2M, homocysteine, PO4).
- SDHD, like its name, thus falls (all solute) short!
- Re volume control:
- Higher frequency dialysis may reduce the interdialytic fluid accumulation period.
- But…if concurrently combined with a reduction in sessional duration, the shorter available intradialytic time for ultrafiltration will effectively enforce an unchanged (and still excessive) volume removal rate, despite any potential reduction in volume accumulation that might result from the shorter interdialytic period.
- Volume removal above all else needs time, and time is the one universal constant that cannot be abbreviated.
Long Hours and High(er) Frequency Dialysis
This is the model sometimes referred to as “intensive,” or “high intensity,” or “extended hour and frequency” dialysis. It is the model first developed in its modern form by Uldall and Pierratos (Canada) and later spread by Lockridge to the US, and by Agar to ANZ. This model delivers both optimal solute clearance and gentle volume correction:
- Deep-compartmental cleaning is possible, as the long sessional duration allows for time-dependent extraction as well as optimal concentration-gradient driven diffusion.
-
A lower ultrafiltration rate—and the abolition of the volume-linked symptoms of rapid dialysis—is achieved through both:
- A shorter interdialytic accumulation period, and thus a lesser volume to remove.
- A longer sessional duration in which to remove a lesser-accumulated volume.
Both time and frequency matter in both target domains
What is abundantly clear is that longer and more frequent dialysis makes sense, no matter from what angle dialysis is viewed. Perhaps the “key” variable for solute clearance is sessional duration, though, clearly, an extended interdialytic period will also bias to greater solute accumulation. Perhaps the “key” variable for volume management is sessional frequency, though, clearly, the greater the abbreviation of sessional duration, the higher the ultrafiltration rate will have to be for any given accumulated volume, even if this is lessened by increasing the frequency of sessions.
So, the final question is…what matters more: solutes or volume?
While both matter, I would contend that volume pips solute at the post. Volume is the cardiovascular bête noir. With the possible exception of potassium, morbidity and mortality in dialysis patients is driven by either (or both) an excessive load of volume accumulation, or an excessive speed in volume contraction.
Rationalising this, 'f' beats 't' by a whisker.
Perhaps this is why, when a decade and a half ago, the two giants of 20th century dialysis (Scribner and Oreopoulos) were pondering their proposal for a measure of good dialysis - the Hemodialysis Product (the HDP) - they decided to square 'f' as they arrived at HDP = t x f2 and not simply HDP = t x f.
While squaring 'f' may be overemphasising its importance, giving it equal value to 't' may also be undervaluing 'f'. Perhaps the truth lies somewhere in between? What is certain, in my view, is that time and frequency are the only two factors that really matter. The rest is noise.
Comments
Dial A Home Doctor
Oct 26, 2020 10:34 AM
greg francis
Apr 15, 2016 4:30 AM
This situation was like this for 17 years I kept active played table tennis, swam twice a week and always walking. My kidney results finally failed and I was on dialysis three times a week for 4 hour sections for just over two years when I decided to only go on for two days a week. Two years later this is still the same much to my Drs disliking. I do very slow dialysis, a pump speed of 280 and a UF rate of 88ml/h , ie I take off 350 mls. Off course I still have full kidney function and on three occasions went for a week without dialysis. This was because I stayed a few days overseas from a Dialysis at Sea cruise in Budapest. Have enjoyed Dr Agar posts wish I had a Dr I could talk to without some harsh words being said . Greg Francis
Dori
Apr 18, 2016 7:17 PM
Corlyn Altier
Apr 02, 2016 10:53 AM
amanda
Apr 15, 2016 2:32 PM
Currently I am fighting this 3 months incenter nonsense. I tried making an appointment with the Director at her office but her office manager ran intereference and has told me she'd call me back and never has. My doctor says I am a good candidate for HHD so I don't know why he won't stand up for me. I have called Davita several times to see if this is a policy with them, no answer. I am frustrated and angry at being treated like a bad child. I am 35 and have a child to take care of. I CANNOT AND WILL NOT LIVE MY LIFE A ZOMBIE! If and when you feel like it shoot me an email maybe we can join forces, apetty74041@yahoo.com
John agar
Apr 16, 2016 12:28 AM
Your two experiences raise the issue of 'when does any one individual patient NEED TO START DIALYSIS?'
This is such an individual decision that it is hard to lay down rules, but one rule that CAN be set for that decision is that it should NEVER be made in response to the eGFR alone ... yet, oddly, the idea that an eGFR should somehow trigger the 'start' response still seems to permeate the thinking of some nephrologists and/or renal services. That said, and while you do not state either your eGFR at start, or that your eGFR was a considered factor in the 'start' decision in your case, I am making an educated guess that it may have been.
Why? ... well, there has been a very disturbing trend - especially in the US - to start dialysis earlier and earlier, long before it is needed, and while considerable residual renal function remains. Was this the case with you? I don't know. Might it have been? Very likely.
Many 'wear' quite severe renal impairment very well. Greg clearly has. Others do. Many will function quite well down to eGFR levels of 5-7 without major symptoms beyond fatigue - a symptom often primarily driven by the accompanying renal (read EPO/Fe++) related anaemia = another component I personally think is under-corrected for in the US because of a strange reticence to adequately restore the Hb.
My guess is that, like Greg, you may be one (of a great many) who have been started too early, both when dialysis was neither necessary or likely to result in 'feeling better'. It may explain why you have been considered 'naughty' where, in truth, you may have simply recognised that you were 'not ready'.
I may be being a little 'out there' on this as I do not know your individual circumstances, so while these comments may not apply to you, there is certainly data that confirms they apply to many.
Back in 2014, I was given the honour of presenting the Opening Plenary Address to the ADC in Atlanta on the topic: 'When to Start Dialysis'. My address, in part, explored the wealth of literature (and this includes not only the IDEAL trial but many similar studies from all around the world:Canada, Sweden, Austraia and New Zealang, Turkey, France and the UK) ... all of which confirm that dialysis often started way too early ... and this is particularly true of the US ... often when the eGFR is still a quite healthy at 12+ or, even worse, at a bouncing 15 or 15+. Why this is so is complex, and I would rather not point fingers here, but simply attest that it is so.
I don't know if this applies to, or was not, 'you' ... but if not 'you' specifically, then there are others who DO fit this picture. While it is true that some patients ARE difficult - often as a combination of reticence, fear, and denial - the decision regarding 'when to start dialysis' requires individualised nuance. It must incorporate a combination of factors that will vary, from patient to patient: it needs mutual trust in the decision and its timing: and it needs mutual cooperation with the planned program. Starting will neither proceed smoothly nor succeed without theses planks in place.
And ... note ... eGFR does NOT figure in that list.
amanda
Apr 17, 2016 3:18 AM
My eGFR is 7%.
Henry P Snicklesnorter
Apr 11, 2016 12:37 PM
As John pointed out, as an Australian, I was trained to dialyse taking care of everything myself. With the excellent training we receive, it has allowed me a trouble free run for all the years I have been on HHD and I have done all of that without a care partner. As a single man, I take care of all my own household chores as well, cooking, cleaning, shopping, laundry etc, ....... and ..... I currently work driving a truck 7 days a week in excess of 80 hrs weekly. In amongst that, I have somehow found time to embark on a new relationship. It's a busy life, but a very satisfying one.
I write this to encourage both you and your man to take steps have him take control of as much of his treatment as he is capable of, relieving you of much of the load you now carry and enhancing both your lives. My description of my personal experience is meant as an example to show what is possible. I wish you both well.
John Agar
Apr 06, 2016 4:29 AM
No ... you don't come across as negative ... you are, just like all dialysis carers and dialysis doers, whether patient or carer or significant other, forced into a situation you didn't ask for, that you didn't expect, and that you hate for the impact it has had on your life, your lifestyle, your dreams and the 'future' you thought you'd have ... and you (as do others like you) rightly feel a dull resentment at having to be there, though you are because of the love your share with and for your husband who is now dependent on your care. As to that last statement - here in Oz, we ensure that the home patient does their own dialysis ... all of it ... and that a carer (as the doer) is NOT required. Slef-care dialysis is our mantra, and we believe it is a far better model ... so encourage your husband to do as much of his own care as you can ... and all, if possible. You have other skills to bring to your partnership - full time demanding work, cooking, buying in, home management and more - and your post demonstrates the very reason why US home dialysis fails so often and so recurrently. The US home dialysis 'failure rate' is several times the rate seen in other countries where the patient is trained as the doer and develops the self-sufficiency and self-pride that accompanies self-care. Dependence on a carer at home simply extends and transfers the learned dependence of a centre-based program into the home = never a good look, nor an effective option. I hear your loneliness and your lack of support, and that saddens and shocks me that your post represents such a persistent and prevalent theme coming from the US. If you have the energy, teach your husband (if no-one else will) to do his own dialysis - as much as he is able. Know that elsewhere, while he self-dialyses, you would be ding the parts of your partnership he cannot - work, income, the other side of caring ... while he manages his own illness. HHD remains the best option (by far) and in my view, NHHD remains the best option in HHD. So ... you are part of the way there. It does get easier with time ... but will be easier still if you care for the home while he cares for his home dialysis.
Henning Sondergaard
Apr 06, 2016 7:48 AM
I concur with Dr. Agar. I think it is extremely important for you and your husband to find a way to share the work. Just like in Australia nobody in my country gets to go home unless they can do their own home treatment by themselves. The US model where a so-called care partner is needed is outdated and it's time to change it. Having someone by your side should always be a 'nice to have' feature, not a 'need to have.'
Most HHD failures in the US is due to care partner burn-out and that is not fair to either the person on dialysis or the care partner.
I think we should start taking the term care partner seriously. You are not a care giver but a care partner - one who can be there as an equal partner, not the person who takes care of everything for him.
I know you guys have only been at it for 3 months now and things might start to get better, but I am pretty sure if you don't let him take over most of his treatment regime things might actually get worse for you. It is an unbearable burden you have put upon yourself with all that you are doing. I know how much energy you put into food and nutrition and into your business. There are only so many hours in the day and that is why I am urging you to find a way where he can do his own treatments and not be so dependent on you.
John agar
Apr 07, 2016 9:26 PM
Ernie Suguitan
Mar 31, 2016 8:15 PM
Dori
Apr 18, 2016 8:13 PM
John agar
Apr 01, 2016 2:46 AM
Amanda Wilson
Mar 31, 2016 12:58 AM
Henry P Snicklesnorter
Mar 29, 2016 1:14 PM
John Agar
Mar 29, 2016 9:58 PM
Beth Witten
Mar 30, 2016 3:03 PM
Amanda Wilson
Mar 26, 2016 2:09 AM
Carol Chamney
Mar 25, 2016 7:31 PM
Debra Null
Mar 25, 2016 3:50 PM
Nieltje Gedney
Mar 25, 2016 2:23 PM
Colin N Mackay
Mar 25, 2016 2:23 PM
Mary Beth Callahan
Mar 24, 2016 10:27 PM