By: Rasha samir Assisstant lecturer of nephrology Mansoura university rashasamirtaha@gmail.com

1. Adequacy of haemodialysis
By
Rasha samir
Assisstant lecturer of nephrology
Mansoura university
rashasamirtaha@gmail.com

2. Mrs A.A , a 49 year old
housewife was brought to
the emergency room with
disturbed conscious level.
The patient was known to be diabetic for
10 years, ESRD on HD for a couple of yrs.
The patient received her last dialysis
session one day before with no reported
problems.
The patient recieves three weekly
sessions each lasting for 3 hours through
a left forearm A-V fistula .
The patient's husband reported that she
was increasingly tired through the past
few weeks. She became more weak and
unable to perform her routine daily
activities.
Her appetite was increasingly poor with repeated complaints of
nausea and vomiting .

3. On examination:
• The patient was confused,
GCS: 11, BL/Pr: 130/80,
pulse: 87, regular, RR: 16,
Temperature: 37.2.
• The upper extremities
showed scattered itching
marks with left forearm A-V
fistula with visible
pseudoaneursms.
• The patient was pale with
puffy eyelids. Bilat oedema
L.L was evident.
• Neurological examination
was unremarkable , no signs
of lateralization or increased
ICP.

4. The patient was resuscitated and the
following investigations were done:
• RBG: 110mg/dl.
• CBC:
HGB: 8.5g/dl, WBCs: 5600, PLT:170,000
• S.creatinine: 10mg/dl.
• S.BUN: 100 mg/dl
• LFTs: Normal
• S.calcium: 7.5 mg/dl
• S.phosphorus: 9.2 mg/dl
• S. Sodium: 141 mmol/l
• S.Potassuim: 6.3 mmol/l
CT Brain showed no abnormalities

5. Do you think what is the most
probable diagnosis?
Why?

7. On examination:
• The patient was confused,
GCS: 11, BL/Pr: 130/80,
pulse: 87, regular, RR: 16,
Temperature: 37.2.
• The upper extremities
showed scattered itching
marks with left forearm A-V
fistula with visible
pseudoaneursms.
• The patient was pale with
puffy eyelids. Bilat oedema
L.L was evident.
• Neurological examination
was unremarkable , no signs
of lateralization or increased
ICP.
The following investigations
were done:
• RBG: 110mg/dl.
• CBC:
HGB: 8.5g/dl, WBCs: 5600,
PLT:170,000
• S.creatinine: 10mg/dl.
• S.BUN: 100 mg/dl
• LFTs: Normal
• S.calcium: 7.5 mg/dl
• S.phosphorus: 9.2 mg/dl
• S. Sodium: 141 mmol/l
• S.Potassuim: 6.3 mmol/l
CT Brain showed no
abnormalities

8. Hemodialysis through its progress allowed
thousands of lives to continue and patients to
prosper even after total loss of the kidneys

9. How to prove
that the dialysis
is adequate?

10. Adequacy is a measure of how well
the dialysis is working
NCDS (National Cooperative Dialysis Study in 1981 suggested that a
minimal dose of dialysis is required.
So the era of adequacy started.

11. How to evaluate adequacy of dialysis?
Improved signs and
symptoms of
uremia
• Tiredness, weakness
• Nausea or poor appetite
• Losing body weight
• Malnutrition
• Anemia
Monitoring the patient's symptoms alone is also
insufficient, since the combination of dialysis plus
erythropoietin to correct anemia can eliminate most
uremic symptoms although the patient may be
underdialyzed

12. Laboratory evaluation
following the blood
urea nitrogen
(BUN) is
insufficient
because a low BUN
can reflect
inadequate
nutrition rather
than sufficient
dialytic urea
removal

13. To see whether dialysis is removing
enough urea,
• Two methods are generally used
to assess dialysis adequacy:
• Either OR
• Both depends upon urea
clearance
• —normally once a month—
URR Kt/v
Clearance
The ratio of removal rate to blood concentration of certain solute
( K is the sympol of clearance)
Why UREA?
An ideal clearance marker:
• Accumulates in uremia;
• Easily measured; and
• Easily removed by the
dialyzer.

14. As the dialyzer blood and dialysate flow rates increase,
solute clearance increases, but at a diminishing rate.
K depend on:
Membrane specification including (pore size , Surface area).

15. URR
• URR stands for urea reduction ratio.
• The URR is one measure of how
effectively a dialysis treatment removed
waste products from the body
• expressed as a percentage.
• Blood is sampled at the start of dialysis
and at the end. The levels of urea in the
two blood samples are then compared.

16. What percentage is optimal?
• Although no fixed percentage can be said to
represent an adequate dialysis, patients
generally live longer and have fewer
hospitalizations if the URR is at least 60
percent.
• Experts recommend a minimum URR of 65
percent.
The URR may vary considerably from treatment to
treatment. Therefore, a single value below 65
percent should not be of great concern, but a
patient's average URR should exceed 65 percent.
only once every 12 to
14 treatments, which
is once a month.

17. O Gotch later used a mechanistic analysis of these data and
showed that the Kt/V of urea was an important measure
of clinical outcome
O The Kt/V is mathematically related to the URR and is in
fact derived from it, except that the Kt/V also takes into
account extra urea removed during dialysis along with
excess fluid so the Kt/V is more accurate than the URR ,
primarily because the Kt/V also considers the amount of
urea removed with excess fluid.
O The correction of total urea removal for volume of
distribution is important because, in a large patient, a
given degree of urea loss represents a lower rate of
removal of the total body burden of urea (and presumably
of other small uremic toxins).
Kt/V came to life depending on urea clearance in 1985

18. The patient who loses 3 kg will
have a higher Kt/V, even though
both have the same URR
Consider two patients with the
same URR and the same
postdialysis weight, one with a
weight loss of 1 kg during the
treatment and the other with a
weight loss of 3 kg. compare
URR to Kt/v

19. Delivered KT/V:
OUsing one of the following formulas:
(a) 2.2-3.3 x (R-0.3-UF/W) [bedside].
(b) kt/v= -In (R -0.008*t)+[(4 - 3.5 R)x (UF/ W)].
OR= BUN before – BUN after.
OUF/W= wt removed during Dx /post Dx
weight.

21. Computer model
• Computer software packages can be
purchased separately or as an integral
component of dialysis machine.
• When supplied with simple clinical
information these programs will perform the
necessary computations & print Kt/V, PCR &
other data.
• Used for two goals:
1- Calculation of the delivered kt/v.
2- Prediction of the delivered kt/v.

22. Drawing Samples for Measuring Urea
Clearance
• Predialysis and postdialysis samples must be
drawn at the same dialysis session.
• Draw predialysis blood from the arterial needle
before administering any saline or heparin.
• With central lines: if heparin and/or saline is
used, withdraw at least 10 cc of blood before
drawing the blood sample. The blood withdrawn
may then be returned to the patient.
• The postdialysis [urea] blood sample must not
be diluted by either recirculation or saline.

23. Significant recirculation should be suspected when there is an
inadequate reduction in the postdialysis (BUN), which should be
less than 40 percent of the predialysis value
Conventional methods of measuring recirculation in HD access include a three
site method performed during dialysis, and a two site technique at the end of
a HD treatment. (BUN) is measured in these samples, and the results entered
into the formula to calculate the percent recirculation.

28. SAMPLING OF KT/V &URR
• Pre-sample: After insertion of the needle.
• Post sample :
A. To prevent rebound ; sequestration of urea from
other tissues into blood to reach equilibrium less
than 2 min after ending,
B. To prevent recirculation ; blood pump is slowed to
30 ml/min for one minute and a sample is taken
from art. line.

29. :Example
Kt = 250 mL/min multiplied by 180
minutes
Kt = 45,000 mL = 45 liters
Vd=60% of body weight
If the patient weighs 90 kilograms
(kg), V will be 54 liters.
V = 90 kg multiplied by .60 = 54 liters.
Kt/V = 45/ 54= 0.8
Contacting Mrs A' nephrologist, he informed that she uses a dialyzer with a
clearance (K) of 250 mL/min and her dialysis session lasts for 180 minutes (3
hours) and she weighs a 90 kg. What is her Kt/V?

30. A single low value is not always of
concern, the average Kt/V should be at
1.2 (based on single pool dialysis model)
The Kidney Disease Outcomes Quality Initiative
(KDOQI) group has adopted the Kt/V of 1.2 as
the standard for dialysis adequacy.

31. What can we do to improve
patients Kt/V?
If a patient's average Kt/V—
usually the average of
three measurements—is
consistently below 1.2, the
patient and the
nephrologist need to
discuss ways to improve it.
What would you suggest?
?

32. Which of the following are items to assess when solute clearance
per session in HD is marginal?
Adequacy of
blood flow from
access
Dialyzer surface
area
Dialysate flow
rate
Time on dialysis
Blood pump
speed
Pre-dialysis
potassium level
Pre-dialysis Na
level
Dialysate
pathway
stagnation
All of the following need to be assessed to see if the clearance is good for
HD session except pre-dialysis K and Na levels which have no clearance
related benefits

33. UREA KINETIC MODELLING
• Urea kinetic modeling is a method for
verifying that the amount of dialysis
prescribed (the prescribed Kt/V)
equals the amount of dialysis
delivered (the effective Kt/V).
• It allows for variations in dialysis time,
use of larger, high efficiency, high-flux
dialyzers, and optimization of dietary
protein needs.
?

34. As the dialyzer blood and dialysate flow rates increase,
solute clearance increases, but at a diminishing rate.
K depend on:
Membrane specification including (pore size , Surface area).
Good flow rate may be difficult to achieve because of vascular access problems.

35. At any given blood flow rate, a dialysate flow rate increase will
increase the clearance
A
Slowing the dialysate flow rate to 300ml/min ( to save on dialysate
concentrate costs) will cause a reduction in dialyzer clearance
compared to dialysate flow rate of 500ml/min
b
At the blood flow rate used in clinical practise, increasing the dialysate
flow rate above 800ml/min usually results in only a small increase in
dialyzer clearance
c
Assume baseline Qb=400ml/min and baseline Qd=500.increasing the
dialysate flow rate by 20% would have much smaller effect than
increasing blood flow rate by 20%
d
Usually the dialysate flow rate is 500 to 800ml/min. which one
of the following statements with regard to the effect of
dialysate flow rate on dialyser clearance is false?
Dialysate flow rate

36. Dialyzer properties
High efficiency versus low efficiency dialyzers
Efficiency is a measure of urea clearance. High efficiency dialyzer has
larger surface area and wider bores compared to low efficiency and hence
higher urea clearance. Dialyzer efficiency is described as K0A measured
ml/min. High efficiency dialyzers have K0A> 700ml/min.
High flux versus low flux dialyzers
Flux is a measure of ultrafiltration capacity described by ultrafiltration
coefficient Kuf. Low flux< 10 ml/hr/mmHg. High flux >20ml/hr/mmHg.
High flux dialyzers have large pores that can help remove bigger
molecules as beta-2-microglobulin

37. The URR of patients in the unit will go up substantiallya
Despite the use of big dialyzer, the predialysis beta-2-microglobulin levels of
the patients in the unit will not go down
b
Both (a) and (b)c
The new big dialyzers did not improve the URR or beta-2-microglobulin
clearance
d
Mrs A' nephrologist, reported that he is planning to switch the whole unit
to new dialyzers with K0A of 1200ml/min and surface area of 2.0 m2.Do
you think which statement would be true?

38. Neither the F5 nor F50 are high-efficiency dialyzersa
The F8 will remove similar amounts of urea as the F50, since F50 is a high flux
dialyzer and the F8 is a low flux dialyzer
b
The F50 and F80 are high flux dialyzersc
Urea clearance with the F8 and F80 will be similar but beta-2-microglobulin
clearance will be markedly different
d
If these dialyzers are available, regrding their properties, which
statement is false?
FluxSurf. Ar.(M2)K0A ureaDialyzer
low0.9550F5
low1.8800F8
High0.9650F50
High1.8850F80

39. Regarding use of high flux dialyzers, which of the following
statements is most correct?
Low-flux dialyzers are now obsoletea
There is no evidence that outcome with use of low-flux dialyzers is
worse than with high-flux dialyzers
b
There is some evidence that high-flux dialyzers may be beneficial in
terms of survival, but this remains controversial.
c
High-flux dialyzers have been shown to be of benefit in non-
randomized trials, and this benefit is probably due to the fact that
such membranes are more biocompatible
d

40. Dialyzer surface area
You have two dialyzers in your unit. One is small, cheap dialyzer, with a
surface area of 0.6m2, and hence a relatively low k0A of 400ml/min. The
other is expensive , 2m2 dialyzer with a K0A of 1000ml/min. the same two
patients: patient 1(Qb=200) and patient 2 (Qb=500) both are on the cheap
dialyzer now. Which one of the following is true?
In the two patients the clearance will increase proportionately in the
same amount after switching to the large dialyzer.
a
The increase in clearance in patient 1 on changing to the large dialyzer
will be negligible and in any case will never exceed the K0A of
400ml/min.
b
There will be little benefit in patient 1 on swithcing dialyzer unless the
dialysate flow rate is increased.
c
The increase in clearance will be substantial in both patients, but the
benefit will be lower in the patient in whom Qb is only 200ml/min.
d

41. Increase Time on Dialysis
The other way to improve the Kt in Kt/V is
to increase t by dialyzing for a longer
period.
If the Kt/V is 0.8 and the goal is 1.2, K is not changed in a 3 hourly
session. how much time you need to add to achieve the goal
• 1.2/0.8 = 1.5,
• so 1.5 times more Kt is
needed.
• This means the length of
the session needs to
increase by 33 percent. If
the inadequate sessions
lasted 3 hours, they should
be increased to 4.5 hrs.

42. Residual renal function(Kr)
• Has insignificant effect on urea clearance during HD. with Kr needs less kt/v.
• Reducing dose of Dx is not a good idea:
• But has a significant effect on lowering predialysis BUN.
• Every 1 ml/min of Kr offers a kt/v of 0.13.
• Consequently patients
Residual kidney functions deteriorates after HD.
Consider the Kr a BOUNDS for the patient.
Interdialytic urine collection.
BUN after and just before next Dx.
Kr = urine volume x urine urea
nitrogen.
Id time/min mean BUN
TOTAL Kt/V = Kt/V + Kr x 5.5
v

43. A well-designed, randomized study
found no benefit of a single-pool Kt/V
target of 1.65 compared with 1.25
Kt/v is a measure of adequate not
optimal dialysis

44. In recent literature, adequacy of dialysis is sometimes confused
with adequacy of other aspects of patient management. So it
is important to distinguish adequacy of the dialysis from
adequacy of patient care.
Dialysis-dependent patients require a number of treatments
independent of or only partially dependent on the dialysis
itself, including management of anemia, nutrition, metabolic
bone disease, diabetes, and cardiovascular disease .
Total kidney replacement requires more than just dialysis, but a minimum
amount of dialysis is still required to optimize both duration and QOL.
Kt/V is only one component of dialysis adequacy.

45. Thank
you