Haemodialysis

Part One

There are two main dialysis options

1. Haemodialysis

            This is the focus of this website and will be discussed hereafter in detail

2. Peritoneal Dialysis

            NB. Although this website does not discuss peritoneal dialysis in any detail, it is an excellent dialysis choice for many patients.

            In our own program, 20-25% of our patients use peritoneal dialysis. Of these, a little over half now use overnight, automated peritoneal dialysis.

            Peritoneal dialysis, though NOT the focus of this website, is both a home therapy and, at least potentially for most, an overnight one too. You should discuss the peritoneal dialysis options with your dialysis unit.

            Further useful information on it can be found at:

                http://www.kidney.org/kls/patients/plu_pd/pd_3.cfm

            Or, to learn about overnight home peritoneal dialysis (APD), try…

                http://kidney.niddk.nih.gov/kudiseases/pubs/peritoneal/

            From now on, however, the focus of this website is entirely on haemodialysis. This is not intended to represent bias – simply that this site is intent on one task alone – to explain the processes of haemodialysis and to introduce you to nocturnal home haemodialysis.
 

Haemodialysis

There are several haemodialysis options. It is important to note that …

            Terminology varies from country to country

            Choices also depend upon both availability and geography

            … That having been said, the three main choices are:

Centre-based haemodialysis

Limited care ‘satellite’ haemodialysis

Home-based haemodialysis

For most patients on dialysis, haemodialysis has, by ‘convention’, always been:

            4 hours, 3 times/week (or some near variant). From here on at this website, this will be called ‘4x3 HD’

            Worldwide, dialysis time per session varies significantly

The average sessional duration in the US is still less than 4 hours and closer to 3 ½ hours.

In other countries and regions, sessional duration is more commonly in excess of 4 hours and in Australia, closer to 4 ½ hours while Japan is closer to 5 hours.

Individual facility-based treatment duration is rarely greater than 5 hours

            Worldwide, dialysis is routinely prescribed only three times per week and thus forces a ‘long break’ on all facility-based patients doing conventional  3x4 HD

BUT … have you ever asked yourself – WHY?

There are three important questions

            1. Is haemodialysis practice based on good science?

            2. Are there smarter, newer technologies around?

            3. Might newer approaches produce better outcomes for patients?

And … there is a fourth and important question – at least, it is a key question for governments and funding agencies …

            4. Can better dialysis be delivered yet at lower cost to the provider (ie:governments and taxpayers)?

When kidneys fail

            They almost always fail permanently and fail in all their functions …

            Little or diminishing waste excretion occurs

            Little or diminishing fluid excretion occurs

            Little or diminishing ‘other functions’ occur

This means that all (or most) wastes ‘stay on board’ and all (or most) fluid swallowed stays inside the body which inevitably …

            Swells the blood volume

            Raises the blood pressure

            Stretches the heart and blood vessels

So … how do we replace the functions of this usually continuingly functioning ‘vital’ organ?

Answer …

At the moment, we use artificial kidney treatment (standard, conventional dialysis) for an average total of 12 hours out of the 168 hr week

            … or 7% of the time

This is to replace the function of an organ system used to running, in the background, 24 hours a day, 7 days a week

            … or 100% of the time

Question …

            Is this enough?

Standard dialysis practice - (4x3 HD)

Is currently performed, in most places round the world, for 4-5 hrs dialysis on Mon/Wed/Fri or Tues/Thurs/Sat … with Sundays off!

This means that …

In 4-5 hrs, all wastes and fluids gained must be removed

This results in a 2nd/3rd daily ‘assault’ on body biochemistry and blood volume

No wonder so many on 4x3 HD feel like they have been run over by a steamroller every other day

So … what governs good dialysis?

Dialyser surface area (m2)

Blood flow rate (pump speed)

Dialysate flow rate

… these factors are easy and popular to adjust … but are relatively ineffective

Dialysis Time

Dialysis Frequency

… these factors are also easy but unpopular to adjust … but are very effective

In my view … ‘optimal’ dialysis should be …

            24 hrs/day, 7 days/wk – just as a pair of normal kidneys would provide - but no-one wants to depend on a machine like that!

            Humans must live, react, inter-act, work, play, love, laugh, weep, enjoy, thrill … all in their waking hours

            Yet, currently, we hook our patients up to dialysis machines in their waking hours, just when they should be doing their ‘living’ things

            So, it stands to reason that optimal dialysis can only be provided for long and often enough if it is provided during sleep, and thus ensuring optimal ‘living time’

… But how?

Let us think about

‘time’ and ‘frequency’

The Key Question

If better dialysis means increasing time, frequency or, best of all, both … is there a way to do that that is not lifestyle-intrusive?

Time

Daytime dialysis time beyond 4-5 hrs is ‘unacceptably intrusive’ for most patients so … the only viable way to increase dialysis time is to perform dialysis during body ‘down-time’ … i.e. during sleep

            Haemodialysis while asleep has long been ‘off-limits’, but …

            Improvements in technology with more creative thinking

            Solutions to the instability of blood pressure … have made night-time dialysis safe

            ... see  SAFETY ON NHHD and DIALYSIS ISSUES

Frequency

Daytime dialysis frequency beyond 3-4 treatments/wk is also ‘unacceptably intrusive’ for many patients so, the best way to increase frequency is to dialyse more often.

This can be done either …

            by shortening the duration of each dialysis … i.e. short (2hr), daily (6days/wk) dialysis (6x2 HD)

            by doing dialysis at night, while asleep, so that the higher frequency of dialysis sessions is masked by being done during sleep

With short, daily dialysis, dialysis exposure/wk is the same as for conventional 3x4 HD - it just turns the 4x3 = 12 hrs into 6x2 = 12 hrs

Short, daily HD (6x2) has both advantages and disadvantages

            As dialysis efficiency is maximal at the start of dialysis, 6x2 HD is more efficient than 4x3

            But ..

            Greater travel time to and from the dialysis centre limits the appeal of short, daily HD unless it, too, is done at home

Time and Frequency

Increasing daytime frequency and time makes during-the-day dialysis totally impractical but … using the night and dialysing while asleep is the clear and only practical way to increase both time and frequency

AND

This use of ‘nocturnal’ or ‘overnight’ time

is now possible and safe due to better equipment and safety options

see SAFETY ON NHHD

            Nocturnal haemodialysis (NHHD) is both safe and practical yet leaves the waking hours undisturbed 

            Increasing time and frequency raises dialysis efficiency. Doubling both the number of treatments/wk from 3 to 6 and the duration of each treatment/wk from 4 to 8 increases the efficiency of waste/fluid removal 4 fold

            This 4 fold increase in efficiency allows:

                        The blood flow rate (pump speed) to be reduced

                        The dialysis fluid flow rate to be slowed right down

                        Dialysis becomes almost ‘subliminal’

And … your circulation sighs a heart-felt ‘thank you’

            The following graphs show the effect that increasing the duration and/or frequency of dialysis has on the build-up and removal of fluid and wastes.

            I have used S.Creatinine measured in mmol/l (SI units) as the ‘y’ (or vertical) axis … but it could represent any waste (or fluid volume) which accumulates and then requires removal during dialysis

Schematic diagram (4hrs x 3/wk) = Conventional (4x3) Haemodialysis

            Waste levels and blood volume fall rapidly over each 4 hr HD (represented    by the red bars) then rise again over 44 hrs (midweek) or over 68 hrs (weekend) … the cycle recurring the next week

Schematic diagram (2hrs x 6/wk) = Daily (short hour) Haemodialysis

            Waste levels and blood volume fall rapidly over each 2 hr HD (represented    by the red bars) then rise again over 22 hrs (midweek) or over 46 hrs (weekend) … the cycle recurring the next week

(continued in the next ‘Part’)