Ant de Villiers to John: could you give a perspective on incremental HD? For those of us who have zero interdialytic fluid gain and are keen to retain RRF as long as possible the modality is attractive.
I am not a fan of incremental dialysis.
While I understand the theoretical idea behind it, I think it would end up, for most patients and in the hands of most dialysis services/clinics as a ‘proper stuff-up’.
Firstly (and mainly) I fear the natural reluctance in human nature that will make most - if not all patients - resist, argue, and down-right refuse to accept or agree to the incremental increase in dialysis time and frequency that would need to be added as the native GFR diminishes.
To that add the difficulties of (1) measuring GFR at low levels (= inexact at the best of times), and (2) the complexity (nay, the impossibility) of measuring native GFR in a patient ALSO receiving concurrent dialysis and who is thus in a permanent state of volume and biochemical flux! The summation of native GFR - in flux and thus fluctuating - and dialysis-generated solute and volume clearance would be nigh on impossible to assess … yet this composite would somehow need to be assessed (I can’t see how) in order to assess the inevitable background decline of native GFR and the rate at which to upscale weekly membrane contact time on dialysis in parallel to the diminishing native component.
For all theses reasons and more, I think IC is a recipe for worse dialysis, and not better.
Say someone started dialysis twice a week, 2-3 hrs to augment their native GFR of 8 or 9. Then, after 2 or 3 months, when that patient has just adjusted to a regimen s/he hates but has come to accept, the nephrologist walzes up one day and says - hmmm, my fuzzy formula (which I can’t rely on) says you now have to have 3 treatments a week. I know what would come back … ‘Why, I don’t feel any different? … sod off!’ Try, then saying 4 hours (or the 5+ hours s/he really needs) and it will inevitably be … ‘no way Jose!’.
It just won’t work! Maybe for the occasional very disciplined patient - perhaps. But for most - no!
Add to that the confusion to dialysis services/programs of trying to roster a large number of patients at different stages of ‘increment’ … and yes, logistics in program management IS an important factor … and I think confusion would reign.
Finally, I (we) do introduce dialysis incrementally - though not really for the same reasons - and I (we) always have. While I admit that I do always start with a 3 x week regimen, the 1st and 2nd run = 2.5 hrs, then the 3rd and 4th = 3 hrs … etc … until full 3 x 4.5 to 5 hr regimen is achieved over the first 2-3 weeks or so. OK - that’s not what is meant by incremental dialysis, but it is a mini-incremental start!
As regards RRF, the evidence suggests that the rate of fluid removal is the key determinant of the rate of loss … each episode of dialysis that imposes an excessive rate of volume removal, ergo drops circulating volume, ergo drops organ perfusion (myocardial stun is well understood but so, now, too, is there evidence for reduced RENAL perfusion with each episode of excessive UFR leading to recurrent episodes of mini-AKI). This is the key cause of the more rapid loss of RRF in HD relative to steady-state PD. For those on HD lucky enough to have zero or near zero sum volume status, then your HD regimen - whatever it may be - isn’t likely to be accelerating your loss of RRF at a rate greater than the rate of loss that your native disease dictates
I could say LOTS more, but that’s enough.
Back to the start, while there is a theoretical argument - though hardly strong - the practical application would be a dogs breakfast and would lead to comprehensively worse dialysis for all but the occasional disciplined, well-informed patient who understood their GFR/dialysis interface as well (or better) than I do.