Hemodialysis Adequacy

Health

1. Dr. Ahmed Akl , MD, PhD
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
HAEMODIALYSIS ADEQUACY
ISN EDUCATION AMBASSADOR
CONSULTANT OF NEPHROLOGY&TRANSPLANTATION,
UROLOGY&NEPHROLOGY CENTER,
MANSOURA,
EGYPT

2. OPTIMAL DIALYSIS
Anemia
management
Good nutritionBP control
Fluid and
electrolytes
hemostasis
BMD
management
Dialysis
adequacy
Kt/v

3. In1913threemedicalscientistsworkingintheDepartmentof
PharmacologyatJohnsHopkinsMedicalSchooldevisedequipmentand
methodsforvividiffusioninanimals;haemodialysiswasinvented.
However, thirty years elapsed before a clinically effective system was designed, by
Willem Kolff working in the Municipal Hospital at Kampen.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

4. THE FIRST ARTIFICIAL KIDNEY
Four artificial kidneysbuilt in 1943 and sent to the UK, the USA, Canada and Poland
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

5. Gordon Murray (1963) Murray’s first dialyser
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

6. The Murray-Roschlau ‘second-generation’ Flat-Plate Dialyser.
•This was an advanced flat-plate parallel-
flow dialyser with:
(NationalarchiveofCanada,MG30B110
D.W.G.MurrayPapers,Volume41,File
16,NegativeNo.C143613;Suppliedby
Dr.W.Roschlau).
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
•30 layers of dialysis units.
•Each unit with two membranes and two
dialysis compartments.
•Forming a dialyser of 0.6 m
2
surface area
and with a priming volume of only 225 ml.

7. Urea (or BUN) levels
•BUNstandsforBloodUreaNitrogen.Withnormalkidneyfunction,a
personhasaBUNintherangeof8-25mg/dl.
Urea is the substance most often monitored in clinical practice because:
•It is a small, readily dialyzed solute that is the bulk catabolite of dietary protein.
•Constitutes 90% of waste nitrogen accumulated in body water.
•Is easily measured in blood.
•Fractional clearance of urea in body water correlates with patient outcomes.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

8. Shooting for BUN Targets
•Inthe1970sandearly1980s,acommonpracticewastoprescribe
hemodialysistherapyinordertoattainatargetBUN.
•Thepre-treatmentBUNnevertoexceed80mg/dl.Toachievethatgoal,
theyadjusted:
•Theamountoftimeondialysis.
•Thebloodflowrates.
•Changeddialyzers.
•Issuedrestrictionsondietaryprotein.
UsingtargetBUNsSeemedlikealogicalapproachtoprescribing
hemodialysis.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
Sad, but true -1970's Renal Dietary Counseling: Stop eating so much protein
OR WE'LL HAVE TO INCREASE YOUR DIALYSISTIME !!

9. Questions No One Could Answer
However,manypatientswhohittingtheseBUNtargetswerestillnotdoing
well,andsomedisplayedsymptomsofbeingunderdialyzed.Whywas
this?
Whydidpatientswhoweighedthesameandatethesameamountofprotein
requiredifferentamountsofdialysistherapytostayhealthy?
Whyweresomepatientswhohadpre-treatmentBUNsof100perfectly
healthy,yetotherswhohadpre-treatmentBUNsof60unhealthyandinneed
ofmoredialysis?
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

10. •TheendresultwasthatGotchandSargentarrivedatasimple,elegant
formulaformeasuringdialysistherapy:
•Theirnewmethodstillutilizedurea,butitdidn'tuseatargetBUN.
Instead,itmeasuredthevolumeofbloodthatwasclearedofureaduring
atreatmentandcomparedittotheamountofwaterinthepatient'sbody.
Using Urea Clearances
•Theyfoundthedatadidn'tmakemuchsenseuntiltheyinventedanew
wayofmeasuringdialysistherapy.
K t
V
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

11. •Analyzedthestudy'sdatabasetryingtofindnew
commonfactorsforthosepatientsthatweredoingwell
(andforthosepatientsthatweredoingpoorly).
National Cooperative Dialysis Study (NCDS)
•Inthe1970's,theNCDSwasfundedtotryto
determinewhichdialysistherapiesprovidedthe
bestpatientoutcomes.
•Ahugedatabaseofinformationaboutdialysis
patientsforthefirsttime.
Prof. Frank Gotch
Dr. John Sargent

12. •TheformulaKt/Veffectivelyansweredthesequestionsforthe
firsttime.
•WhenGotchandSargentappliedtheKt/Vformulatothedatatheyhad
forthesepatients,thehealthyandunhealthypatientsfellintotwodistinct
numericalgroupings.
Urea Kinetic Modeling
•Whyweresomepatientswhohadurealevelsof100perfectlyhealthy,
yetotherswhohadlevelsof60unhealthyandinneedofmoredialysis?
•Whydidtwopatientswhoweighedthesameamountneeddifferent
lengthsofdialysistreatmentstostayhealthy?
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

13. •IfthepatienthadaKt/Vvaluethatwas1.0orhigher,theyweredoing
wellintermsofbeingadequatelydialyzed.
•ThisnewapproachbecameknownasUREAKINETICMODELING.
•Itusestheresultsoftwobloodtests,preandposttreatmentBUNs,inits
calculations.
Urea Kinetic Modeling
•UreakineticmodelingincludesproteinmetabolismanalysesandIt
calculatestheproteincatabolicrate(PCR).
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
•IftheyhadaKt/Vvaluelessthan0.8,theywereunderdialyzedandwere
doingpoorly.

14. AnotherbenefitofGotchandSargent'sanalyseswasthatitprovided
strongscientificevidencethatdialysispatientswerebetteroffeatingmore
protein,notless.
Asmoredataaccumulated,itbecameapparentthatreducingproteinin
thediettokeeptheurealevelslowwasactuallyresultinginpatientsnot
gettingenoughproteintostayhealthy(lowalbuminlevels).
Overtheyears,italsobecameapparentthattherewereadditionallong-
termbenefitsforthepatientsinincreasingtheirKt/Vvaluesto1.2and
higher.
Urea Kinetic Modeling
Atthe1970'spatientswhoatemorethantheirallowedamountofprotein
were"punished"withmoredialysistime.Thatwereactuallyinsyncwith
today'sbestclinicalpractices.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

15. Around1990,researcherswereabletoshowahighdegreeofcorrelation
betweenKt/Vvaluesandureareductionratios(URR).
AURRcanbecalculatedwithsimplealgebraandonlyusesthesame
twobloodtestsastheKt/Vequations.
WhileaURRisnotasaccurateasaKt/Vvalue,nordoesitprovideany
informationaboutthepatient'sproteinintake,aURRvaluedoesprovide
aneasy-to-calculatemarkerfordialysisadequacy.
As an example, a Kt/V of 1.2 is roughly equivalent to a URR of about 63
percent. Like Kt/V, the higher the URR value, the better.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

16. INCREASING DIALYSIS DOSE
IMPROVED SURVIVAL
Kidney Int 1996; 50:550

17. Measures of dialysis
adequacy
•SpKt/V
•eKt/V
•StdKt/V
•URR

18. Urea reduction Ratio
(URR)
URR = 100 x (1-Ct/Co)
Ct = postdialysis BUN
Co = predialysis BUN

19. Urea Reduction Volume
(URR)
Simple
Prediction of mortality
Limitation:
Does not account for the contribution of
UF to dialysis dose
Kt/V=1.1 (UF=0)
Kt/v = 1.35 (UF=10%BW)
URR=65

20. URR & Kt/V

21. Hemodialysis Dose
Measurement
•The preferred method is by formal kinetic
urea modeling
K/DOQI 2006

22. Kt/V
Computerized software
Mathematical logarithm
Kt/v = -Ln (R-0.008t)+(4-3.5xR) x UF
W
Ln= natural logarithm
R = postdialysis BUN
predialysis BUN
UF = Ultrafiltration volume in liters
W = Postdialysis weight in kg

23. BUN Sampling
Predialysis
Postdialysis
Immediate predialysis
Slow flow/stop pump

24. Urea Rebound
Organs with low blood flow (skin, bone,
muscles) may serve as reservoir for urea
70% of TBW is contained in organs that
receive only 20% of CO
So: during HD, there is loss of urea from
well perfused areas, this result in in
BUN over 60 minutes post dialysis.

25. Post Dialysis BUN Sampling
•Avoid 2 rebound:
•Early (<3min post dialysis)
•Access recirculation,begin immediately post
hemodialysis and rebound in 20 seconds
•Cardiopulmonary recirculation, begin 20 seconds post
hemodialysis and is completed in 2-3 minutes after
slowing or stopping the blood pump.
•Late (>3 min)
•Completed within 30-60 minutes due to flow-volume
disequilibrium.

26. Urea Rebound
65% rebound ( >50% is AR,15%CP,31% D)

27. Single-Compartment Fixed Volume
Solute Kinetic Mode

28. 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 (underestimated of true V)

29. Two-Compartment Variable Volume
Solute Kinetic Model

30. 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.
For most patient, urea rebound is nearly
complete in 15 minutes after hemodialysis but
for minority, it may require up to 50-60 minutes
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. Minimum dialysis dose
•SpKt/V > 1.2 US
•eKt/V > 1.2 Europe
•StdKt/V 2.14

32. Daugirdas Formula

33. Prescribed vs. delivered Kt/V
Prescribed Kt/Vis a computerized estimation of
what the patients Kt/V would be, based on the
prescription
• Delivered Kt/V is actual results based on
how the patient really dialyzed the day the
kinetic labs were drawn

34. WhatShouldYouDoifYourPatientKt/VIsBelow1.2orifYourURRIsBelow
65Percent?
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

35. The NKF-K/DOQI Hemodialysis Adequacy Work
Groupidentified several topics pertinent to
implementing and maintaining adequate
hemodialysis.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

36. PATIENTS TO WHOM APPLIED ?
Theseguidelinesapplytoalladult&pediatricHDpatientswithESRD&
negligiblekidneyfunction(GFR<5mL/min)whoreceiveoutpatientHD
threetimesperweek.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

37. EVIDENCE-BASED Versus OPINION-BASED
These guidelines are based on evidencein published
literature & when not available, on consensus opinion
of Work Group.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

38. GUIDELINE 1: REGULAR MEASUREMENT OF THE
DELIVERED DOSE OF HD (EVIDENCE)
The dialysis care team should routinely measure &
monitor the delivered dose of HD.
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39. GUIDELINE 2: METHOD OF MEASUREMENT OF
DELIVERED DOSE OF HD (EVIDENCE)
The delivered dose of HD in adult & pediatric patients should
be measured using formal urea kinetic modeling (UKM),
employing the single-pool, variable volume model.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

40. UREA KINETIC MODELING (UKM)
UKMalsoquantifiestheamountofureagenerated,whichisamarkerofthe
proteincatabolicrate&thereforeofproteinintake.
UKMisamethodforverifyingthattheamountofdialysisprescribed
(prescribedKt/V)equalstheamountofdialysisdelivered(effectiveKt/V).
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

41. CALCULATION OF Kt/V
Kt/VmaybedeterminedbyformalUKMorby
extrapolationfromthefractionalchangeinbloodurea
concentrationduringadialysissession.Thedelivereddose
ofHDmayalsobeassessedusingtheURR.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

42. Formal UKM
Impactofresidualkidneyfunctiononureaclearancecanalsobe
considered.
Advantages:
When rigorously performed, it is a reproducible & quantitative method.
Itprovidesguidanceaboutwhichspecificparametersofprescriptionto
modify,toachievetargetHDdose(dialysistime,dialyzers,bloodor
dialysateflowrates).
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

43. Formal UKM
Disadvantages:
Complexity of calculations requires use of computational devices &
software.
Physical parameters, such as K & V, are difficult to measure & monitor &
actual t can be difficult to determine.
Time required for dialysis staff to collect & process all patient information
to support these calculations can be significant.
Although cost of computers & software is low, it is a factor for some dialysis
centers.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

44. Statistical models
•Ifacomputermodelingprogramisnotavailable,onlyonealternative
methodforcalculatingKt/V(Kt/Vnaturallogarithmformula)&oneother
measurementofthedelivereddoseofHD(URR)shouldbeconsideredfor
routineuseinadults.
•A calculator capable of performing natural logarithms is required.
Kt/Vnaturallogarithmformula(Kt/VLn):
Kt/V=-Ln(R-0.008xt)+(4-3.5xR)xUF/W.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

45. Kt/V natural logarithm formula
Itprovidestheclosestapproximationtothesingle-pool,variable
volumeKt/VderivedfromformalUKM.Itisaccurateoveritsfullrange
(range,0.7to2.1).
Advantages:
ItaccountsforintradialyticvolumechangessecondarytoUF&the
resultantconvectivesolutetransport.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

46. •Itdoesnotpermitrigorous,quantitativeanalysisoftheHD
prescriptions.
(e.g.ifdeliveredKt/Visobservedtobetoolow,Kt/VLndoesnot
provideinsightintohowtherapyshouldbealtered).
Kt/V natural logarithm formula
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
Limitations:
Therefore, the HD Adequacy Work Group does not recommend this method
for primary use.
•AloneitdoesnotsupportcalculationofnPCR(canbederived
fromanomogram,orbyanequation).

47. Urea reduction ratio (URR)
One of the three methods that HD Adequacy Work Group
considered appropriate for measuring delivered dose of HD.
Calculation of URR:
URR = (1 -[postdialysis BUN / predialysis BUN])
Because of its easeof calculation, URR is frequently utilized.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

48. DoesnotsupportcalculationofnPCR&ignorescontributionofresidual
kidneyfunctiontoureaclearance.
Urea Reduction Ratio (URR)
Limitations:
Does not account for contribution of UF to final delivered dose of
dialysis (less accurate).
Errors in delivered dose of HD may be particularly difficult to detect in
target range of URR of > or =65% where a curvilinear relationship
exists between URR & Kt/V.
Correcting observed deficiencies in URR requires empirical
modification of components of treatment prescription.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

49. Percent Reduction In Urea (PRU)
InvolvesthesamecalculationasURRexceptthattheresultis
multipliedby100tobeexpressedasapercentage.
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50. Kt/V Derived From Percent Reduction Of Urea (PRU)
Several equations are proposed to estimate Kt/V from PRU :
Kt/V = (0.026 x PRU) -0.460
Kt/V = (0.024 x PRU) -0.276
TheseequationscorrelatereasonablywellwiththemorerigorousUKM
whentheKt/V&PCRareinthenormalorexpectedrange.
These equations, although reasonably accurate, are not a substitute for
Kt/V Ln formula.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

51. ARE THERE ALTERNATIVES TO Kt/V FOR ASSESSING
ADEQUACY ?
Not all investigators accept Kt/V as optimal method for assessing
HD adequacy.
1-Timedaverageureaconcentration.
2-Soluteremovalindex.
3-Ktthatisnotnormalizedbybodyvolume.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
Othermodalitiesevaluated,include:

52. Timed average urea concentration (TAC urea)
Preferable to Kt/V because it also measures interdialytic urea
generation, thereby allowing estimation of PCR.
It has a major limitation in that poor nutrition (often due to
inadequate dialysis) can lead to a low predialysisBUN & TACurea
that misleadingly suggests that patient is being adequately dialyzed.
Thus, TAC urea must be evaluated in concert with PCR to estimate
protein intake.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

53. Solute Removal Index
Is defined as percentage of total body urea nitrogen content that is removed
by a dialysis treatment.
It is directly measured by multiplying urea concentration in dialysate by
volume of spent dialysate.
Advantages:
1-It is unaffected by factors that significantly alter Kt.
2-Minimizing exposure of patients & staff to blood-borne pathogens.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

54. Limitations:
1-Lack of studies correlating it to patient outcome.
2-Impracticality of collecting the total spent dialysate.
3-Relative inaccuracy of calculated HD dose obtained.
DOQI clinical work group focused their recommendations exclusively upon
blood-based measures of adequacy, suggesting that further research on
solute removal needs to be performed.
Solute Removal Index
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

55. Haemodialysis dose & nutrition
Protein catabolic rate (PCR) in maintenance dialysis
PCR,alsocalledproteinequivalentofnitrogenappearance(PNA),isthe
parameterusedinmostHDunitstoassessdietaryproteinintakeinpatients
whoareinasteadystate.
Itisafunctionofproteincatabolism.
Determinedbymeasuringinterdialyticappearanceofureainbodyfluids
plusanyurealostinurineinpatientswithresidualrenalfunction.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

56. CALCULATION OF PCR
•Itisusuallyexpressedasg/kg/day,aparameterthatisalsocalled
thenormalizedPCR(nPCR).Lesscommonly,thePCRisnot
normalizedtoweight&isexpressedasg/day.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
•Itisroutinelycalculatedbyvariousureakineticmodelingsoftware
programs.

57. CALCULATION OF PCR
•AnotherformulacalculatesnPCRfromtheKt/V&theaverage
BUN:
nPCR=(0.0136XF)+0.251
F=Kt/VX[(predialysisBUN+postdialysisBUN)/2]
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
•Ifacomputerprogramisnotavailable,thefollowingsimpleformulas
willgiveagoodestimateofthenPCR.
nPCR(anuric)=0.22+[0.036XIDriseinBUNX24]/IDintervals

58. CALCULATION OF PCR
Residual renal function
Urinary nitrogen loss must be accounted for in patients with
residual renal function. Thus, for patients with urine output:
nPCR (total) =
nPCR (anuric) + [Urinary UN X150] / ID interval X weight
These formulas cannot be used in patients treated with
continuous peritoneal dialysis, since the BUN is relatively
constant.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

59. OPTIMAL PCR & THE DIALYSIS PRESCRIPTION
•NCDSrecommendedaminimalnPCRof0.8g/kg/day,butatarget
of1.0-1.2g/kg/dayorhigheriscurrentlyrecommended.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
•Asmallpercentageofpatientshavea"high"PCR(>1.2g/kg/day).
TheappropriateresponseshouldbetoincreaseKt/Vratherthanto
restrictdietaryprotein.Unfortunately,thisgenerallyconstitutesa
negativeeconomicincentivetothedialysisfacility.

60. COMPUTER MODELS
Whensuppliedwithsimpleclinicalinformationtheseprogramswill
performthenecessarycomputations&printKt/V,PCR&otherdata.
Computer software packages can be purchased separately or as an
integral component of dialysis machine.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
Usedfortwogoals:
1-Calculationofthedeliveredkt/v
2-Predictionofthedeliveredkt/v

61. The urology & Nephrology center, Mansoura, Egypt
1-Calculationofthedeliveredkt/v

62. e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
2-Predictionofthedeliveredkt/v

67. A variety of factors may result in the actual delivered dose of
HD falling belowthe prescribed dose
1-Compromised urea clearance.
2-Reductions in treatment time.
3-Laboratory or blood sampling errors.
Commonfactorsinclude:
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68. Predialysis blood sampling procedures
When utilizing an AV fistula or graft:
* Obtain blood specimen from arterial needle.
* Do not draw a sample if HD has been initiated.
When utilizing a venous catheter:
*Withdraw any heparin & saline from arterial port of catheter.
*Withdraw another 3-10 mL of blood from arterial port of catheter.
*Connect a new syringe or collection device & draw sample.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

69. Postdialysis blood sampling procedure
At the completion of HD, turn off Qd & decrease UFR to 50 mL/h or off.
Decrease the Qb to 50-100 mL/min for 15 seconds.
Proceed with either slow flow or stop pump technique.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

70. Postdialysis blood sampling procedure
Slow flow sampling technique
*With blood pump still running at 50 -100 mL/min, draw blood sample
from arterial sampling port.
*Stop blood pump & complete disconnection.
Stop pump sampling technique
*Immediately stop blood pump.
*Clamp arterial, venous lines & arterial needle tubing.
*Blood is sampled from arterial sampling port or from arterial needle
tubing.
*Patient disconnection procedure proceeds.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt

71. SUMMARY
1-Preferentialuseofasinglepool,variablevolumemodelfor
calculatingurearemovalduringHDatleastoncepermonth.
e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
2-Quantificationofurearemovalduringasingledialysissession
usingformalureakineticmodelingforadults&children.
4-VigorousefforttoensurepatientcomfortduringHDbyusing
strategiestominimizecramps&hypotension.
3-PrescriptionofaKt/Vof>or=1.4,sothattheminimumdelivered
Kt/Vwouldbe>or=1.2.

72. e-mail : [email protected] urology & Nephrology center, Mansoura, Egypt
It is the duty of the dialysis team to consider implementing
these recommendations
on an individual basis & when not or cannot be applied,
to strive to optimize patient careby offering reasonable &
safe alternative processes of care.

73. Thank You