Improved understanding of current dialysis modalities may hold greater value than technological advances

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understanding dialysis modalities
Mark Lambie

There are several different types of dialysis treatment available to kidney disease patients—with the three major players, in-centre haemodialysis (ICHD), home haemodialysis (HHD) and peritoneal dialysis (PD) all holding their own benefits and drawbacks. Mark Lambie, a senior reader and consultant in renal medicine at Keele University/Royal Stoke University Hospital in Stoke-on-Trent, UK, discusses these modalities in greater detail and assesses whether an improved understanding of each could hold tangible benefits within the wider landscape of dialysis care.

What is the current state of play between the different types of dialysis?

The first thing to note is that we do not tend to think of it as a competitive thing—they are different therapies with different pros and cons, and almost all modality selection is now being done via shared decision-making involving the patient. For a patient who is young, fit and healthy, and has got a job, a home dialysis modality is probably going to be easier than an in-centre regime. And, HHD is more likely to be used by patients who have had a previous transplant, or have been on dialysis before, while PD is often used at an earlier stage, as it is more suited to patients with some residual kidney function.

Ultimately, discussions about any of these being considered as the standard of care are difficult, because it is almost impossible to compare them. This is partly down to the fact nobody will ever be able to do a randomised controlled trial in this area, so we will never know, definitively, how they compare, but it is also because outcomes for each modality are dependent on the context they are being used in. For example, death rates in PD have fallen continuously since the 1990s in the USA—highlighting that any comparisons we could make are specific to the time, place or healthcare system in question, as opposed to being intrinsic to the modality itself.

What are the pros and cons of in-centre and at-home dialysis options?

There is definitely a significant proportion of the population for whom ICHD is the best option—it removes much of the burden on the patient of managing their own treatment and, if you are old and frail, and at risk of becoming isolated, leaving your house regularly for a social environment where you can talk to nurses and other patients holds no small value. On the other hand, ICHD, at least in the UK, tends to be pretty rigid and inflexible, as patients have to undergo four hours of treatment, on three different days, each week, and they have no control over when those slots are. The other big downside is travel. For many patients, transportation to the dialysis centre involves long waits and uncertainty over what time they are going to be picked up or dropped off. This is by far the most common thing patients complain about.

PD and HHD have the same major advantage, which is that they can be done at home, giving the patient more autonomy and flexibility regarding their treatment regime. PD is also a continuous therapy, for the most part, meaning the intensity of the treatment is reduced—as are the fatigue and cardiovascular side-effects that come with regular dialysis sessions—while HHD has the potential to achieve massively greater fluid clearance in patients who have lost their residual renal function. Peritonitis is a significant downside to PD, although it is balanced to some extent by the infection risk of septicaemia in haemodialysis. There is also a storage problem associated with home dialysis modalities, because the amount of dialysate required takes up a lot of space in the patient’s home, and the ongoing responsibility of managing your own treatment, for both PD and HHD, can lead to a sense of burnout over time.

How do you assess the feasibility of a hybrid approach that incorporates the two?

I think it is technically achievable, but the challenges here are less medical and more patient-related, or healthcare expenditure-related. The only country that currently practices that joint model is Japan—whereby, if patients on PD are encountering problems relating to solute or water clearance, they will often be switched to the hybrid therapy to undergo one haemodialysis per week alongside PD. No other country really does that right now, and that is mainly driven by concerns around what you are asking the patient to do by exposing them to the added responsibility, and downsides, of both approaches. The fact healthcare providers will also have to fund both modalities simultaneously makes it very costly as well. We have known for quite a long time that this hybrid approach is an option—and, purely in terms of clinical outcomes, it is going to give the patient more control and improved clearance—but increased expense and treatment burden have prevented physicians and patients alike from embracing it to date.

Do you think new technologies are likely to change the current landscape in dialysis care?

There have been attempts to innovate and improve each of these modalities, and these attempts have been going on for quite some time. Hopefully one of them will come good—but, as yet, none of them have. There are concepts for enabling continuous haemodialysis using a wearable device and there are sorbent technology-based artificial kidneys designed to enhance clearance with PD as well. While these technologies look very good on paper, however, there are still some major technical challenges to overcome, and more proof is needed that they can demonstrate sufficient real-world advantages compared to existing options, with no additional downsides, to justify their use.

One thing that I am personally more interested in right now is the possibility of manufacturing dialysate onsite, as this could help to overcome the storage problem associated with PD especially. While it appears to be technically possible to develop dialysis machines that can manufacture dialysate themselves, the commercial incentives of the companies that make their money selling dialysate is a challenge that we will have to navigate over the next few years. Recently, the most exciting development in haemodialysis has been the introduction of HHD machines that are smaller, more portable and easier to use for patients. Examples of these include the SC+ device (Quanta Dialysis Technologies), the Tablo machine (Outset Medical) and the NxStage system (Fresenius Medical Care). Each comes with its own pros, cons and unique features but, overall, the hope is that they will all facilitate a greater uptake of HHD and enhance the existing benefits associated with this modality.

Where should the focus be for future research relating to dialysis?

One of the bigger issues at the moment is to do with healthcare, and how it is delivered. We know that there is huge variability internationally in how these different modalities are deployed—and we know that, even within the UK, there is huge variability between centres as well. I am a co-investigator for the ongoing Inter-CEPt study, which is a study specifically designed to find out what is driving these UK-wide differences, particularly in home dialysis usage. We will have to wait for the results of this study, of course, but my own personal belief is that these discrepancies are likely to reflect the cultures and attitudes within different units—and how strongly the senior clinicians within these units believe in the benefits of home dialysis modalities. And, following on from this study, one of the main things we need to be focusing on is reducing this unwarranted variation between dialysis units by supporting the centres where home dialysis usage is lower and, ultimately, helping them to increase rates of HHD and PD compared to ICHD.

Expanding this outside of the UK, I think all countries need to be looking at how their long-term interests are best served in terms of dialysis service because, in developed countries at least, it will be cheaper for them to use PD more widely, meaning they need to think about how they are incentivising home dialysis usage. I believe that, for the most part, people have moved away from thinking that increased benefits from dialysis are going to be driven by the next gadget or technical tool. The focus is more likely to be on better understanding what we have already got and trying to improve patient outcomes that way.

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