Peritoneal dialysis , guidelines , cases , , history of adequacy , Optimum dialysis , clinical cases , Clinical Questions , practical calculation , CCPD , CAPD , Kt/V

1. HOW TO IMPROVE
PERITONEAL DIALYSIS
ADEQUACY
BY
AHMED MOSTAFA TAHA MOHAMED
Borham_Ahmad@yahoo
.com

2. ADEQUACY DILEMMA
Frank Gotch introduced the concept of adequacy of dialysis when
he proposed the ‘Urea Clearance’ concept as a measure of
dialysis efficacy.
Over 30 years the concept of adequacy of dialysis has been quite
controversial
And different concepts about (WHAT Adequacy IS?) is it a clinical
state or an absolute Targeted Number ? How can Kt/V which is
widely accepted can cope with the well known truth of reversed
epidemiology in Obese Dialysis patients ?!
How can the Kt/V can give us true picture while it doesn’t look

3. ADEQUACY FROM THE CLINICAL BROAD
VIEW
Control of:
– Acid-base status
– BP and volume status
– Cardiovascular Risk
– Diet/nutrition
– Mineral/Bone disorders
– Small/middle molecules
OR The patient general well Being !!

4. ADEQUACY IN HISTORY
NCDS (National Cooperative Dialysis Study) in 1981 which focused on
HD suggested that there is a Minimal Dose of dialysis that must be
delivered to improve the outcome , so the era of adequacy started .
Data from NCDS analyzed By Gotch and colleagues and the Kt/V came
to life depending on the urea clearance in 1985.
Teehan and colleagues studied Kt/V in PD for 5 years and yielded
weekly target of 1.89 to have better survival in 1994.
Blake and colleagues found no consistent predicitive power of Kt/V in
PD patients.
As studies gave conflicted data and all were small in size and
retrospective , it was clear that we need a larger prospective study

5. CANUSA
In the same time CANUSA Trial was conducted and has these
criteria needed
This was a prospective cohort study of 680 consecutive patients
commencing CAPD in 14 centers in Canada and the United States.
Between 1990 and 1992, Follow-up was terminated December 31,
1993. published in 1996.
It was noted better 2 year survival in weekly Kt/V 2.1 and the
relative risk of death increase when Kt/V decrease from this
target.
NKF-DOQI recommended in 1997 these targets
CAPD Kt/V 2.0 , CCPD Kt/V 2.1 , NIPD Kt/V 2.2 .

6. In 2001 after several reanalysis of CANUSA Data , Found that the
contribution of the residual kidney Function to the total Kt/V was
more predictive of survival the peritoneal Component and they
are not simply equal !
That pushed the recommendations to clinicians to take special
measures to attempt preserving the residual renal function in PD
patients.
Again suspicion about NKF recommendations raised as ADEMEX
Trial in 2002 which was conducted in Mexico as No survival
benefit could be seen if Kt/V was above 1.6 approx. !! So no
benefit for extra cost !
A trial in Hong Kong also confirmed the same results of ADEMEX
as Randomised CAPD patients in 3 groups according to targeted
Kt/V , 1.5 – 1.7 , 1.7 – 2 and > 2.0 , no statistical advantage in

7. Even in HD world in 2002, came the Famous HEMO study with
its results showing that Patients undergoing hemodialysis
have no major benefit from a higher dialysis dose or from the
use of a high-flux membrane .
That pushed the K/DOQI to revise its recommendations as
new studies results and no big benefits gained from the
creatinine use more than the urea, so in 2006 Stated that
“The Minimal deliverd dose of total small solute clearance
should be a total ( peritoneal and renal ) Kt/V urea of at least
1.7 per week “
And further they recommend to be measured after first month
of PD and monitored every 4 months in routine .

8. C J Stefanidis 2001
OPTIMAL AND ADEQUATE DOSE OF PD
Adequate dose: the amount of
PD below which there is an increase
in morbidity and mortality
Optimal dose: the amount
of PD yielding clinical results
which cannot further improve

9. KT/V
K = Molecule clearance t = time V= Molecule Volume of
Distribution
It is a unitless expression.
In Urea usually the Volume of distribution is Total Body Water TBW
which can be assessed by many methods .
In PD usually we use the Urea
Kt = Peritoneal Clearance + Residual Renal Clearance in liters.
V = TBW
Peritoneal urea clearance = D urea/P urea x Liters of dialysate (effluent
)
Residual Renal Clearance = U urea/P urea x Liters of Urine
And to calculate the weekly dose we Multiply by 7 (days number)

10. VOLUME OF DISTRIBUTION
This is variable according to the molecule used .
Usually we use urea and it’s Volume of Distribution equals the
TBW.
TBW is estimated by Watson formula .
Male = 2.447 - (0.09156 x age) + (0.1074 x height) + (0.3362 x
weight)
Female = -2.097 + (0.1069 x height) + (0.2466 x weight)
Also there are other formulas like Hume-Weyers , Chertow's
Bioelectrical Impedance , Mellits-Cheek (kids) .
Some authors use simple formula to calculate = 0.59 x IBW =

11. RESIDUAL RENAL FUNCTION
It is well proved that it shares a bigger effect in the total Kt/V
efficiency more than the peritoneal component.
All Doctors must try to preserve it as possible .
Residual renal urine volume and residual renal Kt/V (rKt/V)
should be measured every 3 – 6 months in patients with a
peritoneal Kt/V (pKt/V) of less than 1.7 weekly, especially if RRF
is rapidly declining. In all other PD patients, rKt/V and urinary
volume should be measured together with pKt/V when clinically
indicated (Canadian Guidelines)

12. It may help clinical understanding use a mean of 24-hour urine
urea and creatinine clearance to express RRF as a glomerular
filtration rate (GFR) in milliliters per minute.
BP should be controlled to less than 130/80 mmHg provided that
this is not associated with signs and symptoms of postural
hypotension or volume depletion .
Angiotensin converting-enzyme inhibitors (ACEIs) or angiotensin
receptor blockers (ARBs) should be strongly considered, unless
contraindicated, in all PD patients with significant (>100 mL
daily) urine output .
Strong consideration should be given to the use of high-dose
oral furosemide (up to 250 mg daily) and oral metolazone (up to
5 mg daily) in all PD patients with significant (>100 mL daily)
urine output, provided that this is not associated with signs and
symptoms of postural hypotension or volume depletion .

13. The effect of PD modality on RRF is controversial.
Some studies showed that automated PD (APD) is
associated with more rapid loss of RRF; others did
not . Randomized controlled trials of biocompatible
PD solutions (with normal pH, low levels of glucose
degradation products, and bicarbonate/lactate
buffer) have not consistently showed better
maintenance of residual renal clearance over at least
1 year of follow-up

14. It is recommended that total Kt/V be measured using 24-hour
dialysate and urine collections soon after the patient has been
stabilized on PD—that is, after 4 – 6 weeks. This is typically the
time when the initial peritoneal equilibration test (PET) will also
be done. If the weekly pKt/V is less than 1.7, and if achievement
of the target total Kt/V depends on residual renal clearance, it is
important that rKt/V be re-measured every 3 – 6 months
because it will tend to decline with time. If the rKt/V is no longer
sufficient to maintain the total Kt/V at target, the peritoneal
prescription needs to be increased, with the total Kt/V being re-
measured until the target is achieved. If the weekly pKt/V is
greater than 1.7, it is not likely to change substantially while the
peritoneal prescription remains the same. It is therefore not
essential to re-measure pKt/V routinely unless there is an
unexplained or unexpected change in the patient’s clinical or

15. CANADIAN SOCIETY OF NEPHROLOGY
GUIDELINES/RECOMMENDATIONS
Small solutes clearance :
For continuous ambulatory PD (CAPD), the usual starting
prescription need not exceed 4×2-L exchanges daily .
If patients are experiencing uremic symptoms or are clinically
not doing well, and if there is no identifiable cause other than
insufficient dialysis, the prescription (that is, the pKt/V) should
be increased, especially if the total Kt/V (that is, the pKt/V and
rKt/V combined) is less than 1.7.
For CAPD, lower volumes or fewer exchanges than 4×2 L daily
can be used for smaller individuals or for those with significant
RRF, especially if the total Kt/V is greater than 1.7

16. For APD, the recommended starting prescription should be
designed to achieve a target total Kt/V of 1.7 or more, and
should take into account membrane transport characteristics,
with the number of nighttime exchanges typically ranging from 3
to 5
A measurement of total Kt/V should be carried out 4 – 6 weeks
after initiation of PD . The measurement of total Kt/V should be
repeated if there is an unexplained or unexpected change in the
patient’s clinical status or a problem with ultrafiltration (UF)
Strategies that are effective when attempting to raise clearance in
CAPD are increases in dwell volume and addition of extra
exchanges ; however, the small risk of mechanical complications
should be considered when dwell volumes are increased, and the
substantial risk of noncompliance should be considered when a
fifth manual exchange is added

17. The most effective strategy when attempting to
raise clearance in APD is to ensure that the patient
has a day dwell. The next most effective strategies
are the introduction of an additional day dwell (that
is, 1 daytime exchange) and larger nighttime dwell
volumes . Other options to consider are increasing
the cycler time and the frequency of cycles.
In a patient who is underweight or overweight, the
calculation of Kt/V should use the patient’s ideal
body weight to estimate V .

18. CASE 1
How to calculate Kt/V in CAPD patient ?
Male CAPD patient 70 kg, with 4 exchanges , 2 L each , total
volume drained per day is 9.5 L which is Vdialysate( UF 1.5 L/D) ,
we will take sample from effluent of each exchange and either
measure the urea in each then calculate the average or take a
sample from each and mix them , then analyze them to have the
mean of dialysate urea which was 72 mg /dl = Durea.
Blood urea = Purea = 80mg/dl
So Kt = Durea/Purea x Vdialysate = 72/80 x 9.5 = 8.6
V=TBW= 70 x 0.58 = 40.6 L

19. So daily Kt/V = 8.6 /40.6 = 0.21
Weekly peritoneal Kt/V = 0.21 x 7 ( No. of days in week) =1.47
For RRF Kt/V is calculated also
His urine output 1 L per day (Vurine) , Uurea = 180mg/dl ,
Purea=80mg/dl as mentioned before so
Kt =180/80 X 1 = 2.25
Daily Renal Kt/V = 2.25 /40.6 = 0.055
Weekly Renal Kt/V = 0.055 X 7 = 0.38
Total weekly Kt/V = Renal Kt/V + Peritoneal Kt/V = 1.47 + 0.38
= 1.85
Which is within accepted target of adequacy.

20. CASE 2
How to calculate Kt/V in APD patient ?
Same Male patient transferred to CCPD Modality , 70 Kg , we
calculate the night and day separately then we add to them the
renal Kt/V
with 4 night exchanges ( total with UF 9 L) , D urea = 58mg/dl ,
Purea= 80mg/dl
Night Kt=58/80 X 9= 6.5
wet day with one dwell ( total with UF 3 L) , Durea = 75mg/dl
Day Kt = 75/80 x 3 = 2.8
So Peritnoeal daily Kt/V = (Night + day)/V= (2.8 + 6.5)/40.6 =
9.3/40.6=0.23

21. Residual kidney Weekly Kt/v from previous calculation = 0.38
So total weekly Kt/V = 1.61 + 0.38 = 1.99
Which is within accepted target of adequacy.

22. QUESTION
A 55 years woman has been on peritoneal
dialysis for 3 years. She has had declining
residual renal function. She used to have a Kt/V
urea of > 2.2, but now her Kt/V urea is 1.81.
The woman states that she feels great, and no
different from how she felt a year ago when her
Kt/V urea was 2.12. Her dialysis nurse is
insistent that she increase the size and number
of dwells, despite the reluctance of the patient.

23. The best evidence to back up the patient’s claims would be which
statement:
– A. More than one RCT has shown no worse outcome with Kt/Vurea
1.7-2.0 versus >=2.0.
– B. More than one observational trial has shown no worse outcome
with Kt/Vurea 1.7-2.0 versus >= 2.0.
– C. More than one RCT has shown African Americans have
equivalent outcomes with Kt/Vurea 1.7-2.0 versus > 2.0
– D. More than one observational trial has shown that Kt/Vurea is
not the optimal measurement of PD adequacy.

24. CORRECT ANSWER IS A