The Keys to Nocturnal Home Hemo
One of the problems I keep returning to in response to so many of the things people write about nocturnal dialysis is the variability of the beast we try to pigeonhole as one single modality. In reality, it is as variable, changeable, and different as the weather!
A recent post at the DaVita site is, in my view, one such case in point.
The term “nocturnal hemodialysis” (NHD) or “nocturnal home hemodialysis” (NHHD)” tends to be applied as if they are one single entity. This can be potentially dangerous if it is not appreciated that nocturnal treatments…
- …can be delivered either at home, in a sleep-over centre, or just about anywhere there is a protected power source and access to water and a drain (unless using a pre-packed dialysate system like NxStage).
- …can be performed on and or by any dialysis system/machine, and that undertaking nocturnal dialysis using a low-flow system like NxStage (the most common US option) is totally different from overnight dialysis using a single pass platform like Fresenius, Baxter/Gambro, B-Braun, Nikkiso, Belco, etc.—totally different—and that the settings, flows, and “biochemical mindset” of the dialysate all need to be individualised.
- …can range anywhere from 6 to 9 hours per session (NB: most—but not all—of our patients at home trend to 8 hours).
- …can be run with dialysate flow rates ranging from 100 ml/min (the Uldall/Pierratos original model, and a NxStage trend) up to 500 ml/min (though a DaVita clip quotes up to a whopping 800).
- …can be 3 nights a week in a centre with a long break built in, or up to 6 (or even some still 7) nights at home (NB: most of our patients trend to a 4 or 5 night/week profile, with many using the mix and match option of a 2 nights on, 1 night off regimen).
- …can be run at a giddying array of pump speeds from 200 ml/min to (ye gods) 450+ (NB: all of ours sit fairly and squarely at 225-250 ml/min).
- …demand an individually determined dialysate composition. This is an area that can be seriously misinterpreted or confused by the dangerous schism between modern SI units (used by the whole world, ex-US) and the older mg/dL units (used by the US, ex-everyone else).
Using the vastly more common SI unit practice, this may mean that:
- Calcium (commonly here 1.6 mmol/L) can be anywhere from 1.5 to 1.75 for NHD, determined by biochemistry checked pre- and post-bloods, taken each 6 weeks.
- Phosphorus may, or may not need to be added to the dialysate—usually only in frequent and long NHD … (NB: quite commonly, but not always, from 10 - 40 ml Fleet enema pack is added to the dialysate pre-dialysis by our patients). Again, this must be determined, individualised and varied according to biochemistry checked pre- and post- bloods, taken each 6 weeks.
- Potassium (NB: commonly here 3K) should also be individualised. It would only rarely be set as low as 2K, as with long, slow, gentle dialysis, transcompartmental K+ equilibration balances DURING, not after, dialysis, and using a 2K bath can lead to potential hypokalaemia. The more frequent regimens commonly used at home prevent pre-dialysis hyperkalaemia, but the K+ dialysate may also need to be varied, determined by biochemistry checked pre- and post- bloods, taken each 6 weeks.
- Dialysate is buffered by bicarbonate (preferred), or by lactate (like the NxStage) …a buffer that I believe to be less ideal.
- And, I haven’t (and won’t) even mention sodium, or my old head might spin…but that matters too.Having the ability to modify the dialysate is, in my view, a major advantage, though it can also introduce error and should be practised with care.
- Volume removal was quoted in the DaVita article as “up to 7 L” (yes .. seven) litres!??? Seven litres is a simply astronomical volume load to need to remove … and, in my view, it is unforgivable if that quantum of volume gain is being accepted as “OK”. To me, it is simultaneously both dangerous and frightening! Removal should commonly be at an ultrafiltration rate of no more than 150-250 ml/hr. (See this blog post, too.) Let me just do the maths: at 250ml/hr, that means 1L per 4 hours, or 2L in an 8 hour run. So, where does 7 litres get a look in? Two litres is pretty much line-ball with a healthy person’s average daily fluid intake, so to take 2L off on dialysis the following night is no issue. If there is a 2-day break, we would then suggest scaling back the fluid intake to 1.5 litres/day (plus an additional amount to match in volume any urine output for the period). This should not be too draconian, or difficult, and would still only lead to 3 litres to remove in the next 8 hour dialysis, and require a removal rate of 1.5 litres each 4 hours or around 350 ml/hour: a rate that remains inside the average plasma refill rate!
- Here in Australia, I talk “interdialytic fluid caution” to my NHD patients if their hourly UFR is creeping towards 300 ml/hr, and I suggest a slightly longer run if it is creeping anywhere up near 350 ml/hr. Most of our patients remove comfortably less than 2.0 litres per 8 hour run, with a 2.5L (max) per run.
Lastly—though it is the most important of all, is the patient him/herself. Dialysis patients come in a myriad of shapes and sizes, ages and gender, experience, courage, anxieties and fears, with or without attendant co-morbidities, and with variable family support. In addition, many are lone individuals. Each of these characteristics tempers patient ability, their treatment site and the possible delivery options, and all must be individually taken into account as a plan to impart the maximum autonomy possible is developed with and for each individual.
And that word—individual—brings me to my final point.
The NHD “prescription”—though I dislike the word “prescription” intensely when used to describe dialysis, as it makes the infinitely personal and individual process of dialysis sound like a pill—must be individualised to each patient.
The sessional length and frequency needs to be varied across the altering timing or circumstances of each individual patient… and within each patient. This emphasises the dictum that must apply in the good management of nocturnal dialysis, a dictum that towers above all others: “know thy patient well.”
To blanket “prescribe” is to court disaster.
And aware, here, that I may step on toes by saying this, it is just this infinite individuality of need and fit that gets my goat when I scan the conversations at the HDC FaceBook site, where utterly well-meaning patients offer their “prescription settings “ as if they are correct and right for others. That simply cannot be.
Everyone is different, and must have their care individualised to and for them, alone. But, unfortunately, many of us—their advisors—don’t seem to get this either.
Here, I have just dealt briefly with NHD and NHHD in all its myriad guises. Centre-based care, is an even greater mine-field, as it must be (or at least should be) individualised too, and this even more demanding and difficult to achieve. That said, it still behoves us to try! However, centre-based variability is a whole different subject.
For now, that is my “take” on NHD, for its two-penny’s worth.