ADEQUACY OF HEMODIALYSIS

HEMODIALYSIS ADEQUACY

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.

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

10. 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

11. 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 ?

12. 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

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

14. 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

15. 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)

16. 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.

17. 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

18. 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)

19. 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 .

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

21. 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 . In patients with significant residual native kidney function (Kr), the dose of hemodialysis may be reduced provided Kr is measured periodically . 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

22. 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.

23. 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.

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

25. 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.

26. 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.

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

28. 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.

29. 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

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