Haemodialysis Part One

Haemodialysis Part One

There are two main dialysis options

1. Haemodialysis

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

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

n 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.

n Further useful information on it can be found at:

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

Or, for a good site for learning 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 …

n Terminology varies from country to country

n Choices also depend upon both availability and geography

… That having been said, the main choices are:

n Centre-based haemodialysis treatment

n Limited care ‘satellite’ haemodialysis treatment

n Home-based haemodialysis treatment

For most patients on dialysis, haemodialysis has always been:

n 4 hours, 3 times/week (or a near variant). From here, this is called ‘4x3 HD’

n Worldwide, dialysis time per session is still often less than 4hrs and rarely greater than 5 hours

n Worldwide, dialysis is routinely prescribed only three times per week

BUT … have you ever asked yourself – WHY?

There are three important questions

n Is haemodialysis practice based on good science?

n Are there smarter, newer technologies around?

n Might newer approaches produce better outcomes for patients?

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

n Can better dialysis be delivered yet at lower cost to the provider (read to government and the taxpayer)?

When kidneys fail

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

n Little or no waste excretion occurs

n Little or no fluid excretion occurs

n Little or no ‘other functions’ occur

This means that all waste ‘stays on board’ and all fluid swallowed stays inside the body which inevitably …

n Swells the blood volume

n Raises the blood pressure

n Stretches the heart and blood vessels

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

n We use artificial kidney treatment (standard, conventional dialysis) for an average total of 12 hours out of the 168 hr week (or 7% or the time)

Standard dialysis practice - (4x3 HD)

Is currently performed, in most places round the world, for

n 4-5 hrs dialysis on Mon/Wed/Fri or Tues/Thurs/Sat … with Sundays off!

… this means that …

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

n This is a 2^nd/3^rd daily ‘assault’ on body biochemistry and blood volume

n 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?

n Dialyser surface area (m²)

n Blood flow rate (pump speed)

n Dialysate flow rate

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

n Dialysis Time

n Dialysis Frequency

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

Optimal dialysis should be …

n 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!

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

n Yet, currently, we hook our patients 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 provided during sleep, thus ensuring optimal ‘living time’

… But how?

Time and frequency

Better dialysis means increasing time, frequency or, best of all, both…

1. Time

n Daytime dialysis time beyond 4-5 hrs is ‘unacceptably intrusive’ for most patients

n The only viable way to increase dialysis time is to perform it during body ‘down-time’ … i.e. during sleep

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

n Improvements in technology with more creative thinking

n Solutions to the instability of blood pressure

… Have made night-time dialysis safe ... see SAFETY ON NHD and DIALYSIS ISSUES

2. Frequency

n Daytime dialysis frequency beyond 3-4 treatments/wk is also ‘unacceptably intrusive’ for many patients

n The best way to increase frequency is to dialyse more often but shorten the time of each dialysis … i.e. short (2hr), daily (6days/wk) dialysis (6x2 HD)

n Dialysis exposure/wk is the same - it just turns 12 hrs (4x3) into 12 hrs (6x2)

n 6x2 has both advantages and disadvantages

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

n Greater travel time limits the appeal of short, daily HD (unless it, too, is done at home)

3. Time and Frequency

n Increasing daytime frequency and time makes during-the-day dialysis totally impractical

But …

n Using the night and dialysing while asleep is the clear and only practical way to increase both time and frequency

n This use of ‘nocturnal’ time is now possible and safe due to better equipment and safety options

see SAFETY ON NHD

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

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

n This 4 fold increase in efficiency allows:

n The blood flow rate (pump speed) to be reduced

n The dialysis fluid flow rate to be slowed right down

n Dialysis becomes almost ‘subliminal’

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

The following graphs illustrate 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’ axis … but it could represent any waste (or fluid volume) which accumulates and 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)