HEMODIALYSIS ADEQUACY Presenter Dr. Md.Azizur Rahman Resident Department of Pediatric Nephrology

Definition Dialysis adequacy is defined as the minimum amount of urea clearance and nutritional intake that prevents adverse outcomes. ( Avner) 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

Aspects of dialysis adequacy Clinical Height and weight gain (nutrition) Control of anaemia, acidosis Control of bone disease. Control of BP. Relief of uremic symptoms Quality of life and life expectancy .

Measurement Small solute clearance (urea kinetic modelling (UKM), Kt/V and/or urea reduction ratio (URR)).

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.

The clearance of urea has been selected as the basis for all the calculations of dialysis adequacy WHY UREA ? MW 60, only slightly toxic per se a marker for small MW uremic toxins Urea removal < ---> other small toxin removal

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.

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. It is not commonly used because of its complexity.

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

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

What is Kt/V ? 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

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

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

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

Single-Pool vs Double-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.

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

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)

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.

Minimum dialysis dose URR >65% SpKt/V > 1.2 US eKt/V > 1.2 Europe StdKt/V 2.0

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.

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.

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

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.

Errors of incorrect blood sampling: • If the sample is contaminated by blood from the dialyser, or heparin, or if there is recirculation, the urea result will be underestimated, giving a falsely high kt/V ; • the earlier the blood is drawn after the completion of dialysis, the higher the apparent delivered dose, as urea rises rapidly postdialysis;

Methods Of Standardization Of Post-dialysis Sampling • Stop dialysate flow is the most commonly used, but gives higher results; • Stop-dialysate-flow method — stop dialysate flow, but keep blood pump running for 5 min; take sample from anywhere in circuit.

Ensuring adequacy Kt/V UK and US guidelines suggest 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.

Causes of Inadequate Dialysis • Improper dialysis prescription • Inadequate blood fl ow • Reduction in treatment time • Dialyzer clotting, leaks • Recirculation

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.

Home Message Measures of adequacy in children have not been defined, but consensus standards propose that they should be equal to or better than adult recommendations of > 1.2 for Kt/V and > 65 % for URR.

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

Thank You All