1. Dialysis adequacy refers to removing sufficient toxins and waste from the blood to prevent adverse health outcomes and is measured by urea clearance and nutritional intake. 2. Urea clearance is the standard measure and is expressed as Kt/V, with a target single pool Kt/V of at least 1.2 per session for patients receiving hemodialysis 3 times a week. 3. Other factors that determine adequacy include residual kidney function, nutrition as measured by normalized protein catabolic rate, and controlling symptoms like anemia, acidosis, and blood pressure.

1. HEMODIALYSIS ADEQUACY

2. Definition
• Dialysis adequacy is defined as the minimum
amount of urea clearance and nutritional intake
that prevents adverse outcomes.
• Adequacy of dialysis refers to how well we
remove toxins and waste products from the
patient’s blood, and has a major impact on
their well-being

3. Aspects of dialysis adequacy
• Clinical
Control of anaemia, acidosis
Control of bone disease.
Control of BP
Relief of uremic symptoms
Quality of life and life expectancy

4. • Measurement
• Small solute clearance (urea kinetic modelling
(UKM)
• Kt/V
• urea reduction ratio (URR)).

5. How do we know if a Patient is
Adequately Dialyzed ?
• The National Cooperative Dialysis Study (NCDS)
established urea kinetic modeling (UKM) as the
accepted method of measuring small solute
clearance.

6. Moleular Weight of 60
a marker for small MW uremic toxins
Urea removal < ---> other small toxin
removal
WHY UREA ?
The clearance of urea has been selected as the
basis for all the calculations of dialysis adequacy

7. Urea Clearance Factor
• The urea clearance coefficient of the dialyzer
• The pre and post treatment blood urea
• The treatment time,
• The total body water,
• The UF,
• Residual renal function and
• The interdialytic urea generation rate.

8. UKM
• When calculations of dialysis adequacy use
both urea clearance and patient nutritional
status (i.e., urea generation rate), this is called
UKM.
• It takes into account residual renal function,
predicted dialyser clearance, blood and
dialysate flow, time on dialysis and fluid
removal.

10. Measures of dialysis adequacy
• URR
• spKt/V = single pool
• eqKt/V = equilibrated (Double pool)
• Std Kt/V = weekly standard

11. URR
• It is calculated as follows:
[(Pre-dialysis urea – post-dialysis urea)/Pre-
dialysis urea] × 100.
• Simple
• Prediction of mortality
Limitation:
• Does not account for the contribution of UF to
dialysis dose

12. Kt/V = fractional urea clearance
K = dialyzer clearance (ml/min or L/hr)
t = time (min or hr)
V = distribution volume of urea (ml or L)
K x t = L/hr x hr = LITERS
V = LITERS
Kt/V = LITERS/LITERS = ratio
What is Kt/V ?

13. • K stands for the dialyzer clearance, the rate at
which blood passes through the dialyzer,
expressed in milliliters per minute (mL/min)
• Kt, the top part of the fraction, is clearance
multiplied by time, representing the volume
of fluid completely cleared of urea during a
single treatment

15. spKt/V = single pool
eqKt/V = equilibrated (Double pool)
Std Kt/V = weekly standard
Kt/V

16. • A urea Kt/V value <0.8 was found to be
associated with a high likelihood of morbidity
and/or treatment failure, while a Kt/V >1.0
was associated with a good outcome
• Guidelines have recommended a minimum
Kt/V value of at least 1.2 for hemodialysis
patients being dialyzed three times per week

17. spKt/V
• The single pool Kt/V assumes that, at the end
of dialysis, the concentrations of intracellular
and extracellular Ur are equal
• (Upre, urea pre-dialysis; Upost, urea post-dialysis; UFvol,
volume removed on dialysis)

18. Single-Pool vs Double-Pool
Single-pool
• Does not account for urea transfer between fluid
compartments
• With  dialyzer clearance, urea removed from
extracellular compartment can exceed transfer
from intracellular compartment
• Urea rebound (30-60 min)
• So Dialysis dose will be overestimated if this urea
pool is large.

21. Equilibrated Kt/V
• eKt/v is 0.2 units less than single-pool kt/v, but
it can be as great 0.6 unit less.
• urea rebound is nearly complete in 15 minutes
after hemodialysis but may require up to 50-
60 minutes

30. Contd.
• The degree of rebound is high in small patient
• eKt/V= spKt/V - 0.6 x (spKt/V) / t + 0.03 (for
arterial access)
• eKt/V= spKt/V - 0.47 x (spKt/V) / t + 0.02 (for
venous access)

31. STANDARD Kt/V UREA.
The so-called “standard” Kt/V urea grew out of
two desires:
(1) to come up with a measure of hemodialysis
adequacy that was not dependent on number of
treatments per week and
(2) to have a measure where the minimum dose
for hemodialysis would be similar to the
minimum dose for peritoneal dialysis.

32. Minimum dialysis dose
• URR >65%
• SpKt/V > 1.2
• eKt/V > 1.2
• StdKt/V 2.0

33. 1. To recommend a target single pool Kt/V (spKt/V) of 1.4
per hemodialysis session for patients treated thrice
weekly, with a minimum delivered spKt/V of 1.2.
2. In patients with significant residual native kidney
function (Kr), the dose of hemodialysis may be
reduced provided Kr is measured periodically.
3. For hemodialysis schedules other than thrice weekly, a
target standard Kt/V of 2.3 volumes per week with a
minimum delivered dose of 2.1 using a method of
calculation that includes the contributions of ultrafiltration
and residual kidney function.
Measurement of Dialysis: Urea Kinetics

34. Clearance of other molecules:
• ‘ Middle ’ molecule clearance thought to be
important to prevent the long-term complications
of dialysis.
• B2 microglobulin is the most used marker.
• Phosphate clearance is also important and
appears to correlate more with hours of dialysis
than rate of small molecule clearance.

35. Normalized protein catabolic rate (nPCR)
• A measure of Ur generation, which reflects
nutritional status. Ur generation will broadly
reflect protein intake.
• It is felt that patients require an nPCR
>1.0g/kg/day.
• nPCR of <0.8g/kg/day is associated with
higher mortality.

36. Nutrition
Targets:
• Serum albumin >35g/L.
• Normalized protein catabolic rate (nPCR)
>1.0g/kg/day.
• Acceptable anthropometric measures.

37. Residual function
• When HD is first commenced, residual renal
function may contribute greatly to the total
amount of solute clearance (Kru).
• This is usually calculated with a 24h urine
collection.
• Residual function tends to diminish quickly on
HD.

38. Ensuring adequacy
• Kt/V
a sp Kt/V >1.2 for patients dialysed x 3/week,
equating to a URR of ~65%.
• Residual renal function should always be taken
into account.

39. Causes of Inadequate Dialysis
• Improper dialysis prescription
• Inadequate blood flow
• Reduction in treatment time
• Dialyzer clotting, leaks
• Recirculation

40. How to improve clearance?
 Improve vascular access — if flows are poor
or if there is access recirculation, it will be hard
to improve clearances.
 Increase blood flow/larger needles .
 Increase dialyser size — modest impact.
 Increase dialysate flow.
 Increase dialysis time/frequency — major
benefit.
 Consider HDF.

41. Home Message
Dialysis can be considered adequate if it provides
 relief of uraemic symptoms and
 controls acidosis,
 Control of BP,
 Correction of anemia
 fluid & Electrolyte balance,
 feeling of physical and psychological well-
being

42. references
• KDOQI Hemodialysis Adequacy-Clinical
Practice Guideline Update 2015: What You
Need to Know by NKF
• Daugirdas dialysis book
• Questionnaire from journals