ASN DIALYSIS ADVISORY GROUP...This image cannot currently be displayed. Goals For A Successful HHD Prescription • SOLUTE REMOVAL • Small solute target: std Kt/V > 2.0 • Achieved

ASN DIALYSIS CURRICULUM

ASN DIALYSIS ADVISORY GROUP

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Writing the Home Hemodialysis (HHD) Prescription

Joel D. Glickman, MD

•Professor of Clinical Medicine

•Perelman School of Medicine

•University of Pennsylvania

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Goals For A Successful HHD Prescription

• SOLUTE REMOVAL

• Small solute target: std Kt/V > 2.0

• Achieved with lower spKt/V than in-center HD

• For 5 treatment per week target spKt/V ~ 0.55 - 0.60

• For 6 treatment per week target spKt/V ~ 0.45

• Phosphate clearance

• Middle Molecule clearance

• FLUID REMOVAL

• Avoid high ultrafiltration rates

• QUALITY OF LIFE

• Need to match prescription to patient lifestyle

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Presenter

Presentation Notes

SOLUTE REMOVAL: There are no studies that examine relationship between urea clearance and outcomes in HHD -std (standard Kt/V) has not been clinically validated as a correlate of outcomes in HHD -KDOQI recommends a target STD Kt/V of > 2.0 Relationship between spKt/V and STD Kt/V is defined by the formula: stdKt/V = 168*[1-exp(-eKt/V)]/t/[(1-exp(-eKt/V))/eKt/V+168/N/t-1] (Gotch, FA, Nephrol Dial Transplant (1998) 13 [suppl 6]:10-14) (See ASN Hemodialysis Curriculum: Hemodialysis solute transport and assessment of adequacy.” Dr. Brent Miller) Hemodialysis prescription should also try to maximize phosphate and middle molecule clearance QUALITY OF LIFE: - Patients on home hemodialysis accept huge responsibility and accept increase burden of therapy in order to realize improvement in quality of life and outcomes. The prescription needs to take into account patient lifestyle and minimize burden when possible. Patients on short daily HD spend many waking hours on treatment and often prefer minimizing treatment time. Nocturnal HD patients have less burden because they “multitask” – sleep and dialyze at the same time. If patient quality of life and burden are not addressed patients may “burn out” and drop out.


Typical Treatment Parameters For HHD

Traditional Equipment

NxStage

“Low dialysate volume approach”

Conventional HD

SDHD* NHD** SDHD NHD

Treatments/Wk 3 5-6 5-6 5-6 5-6

Treatment Time (Hrs)

4 2 6-8 2.25-3 6-8

Qb (ml/Min) 400 400 200-250 400 200-250

Qd (ml/Min) 600-800 600-800 300 130-200 60-80

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* SDHD = short daily hemodialysis** NHD = nocturnal hemodialysis

Presenter

Presentation Notes

This chart demonstrates the number of treatments per week with each type of hemodialysis, along with typical treatment time, blood flow rate and dialysate rate. Nocturnal hemodialysis has half the blood flow rate of the other methods, and a much lower dialysate rate than the other options, as a result of the longer treatment time. SDHD prescriptions using traditional dialysis equipment is very similar to conventional HD except treatment time is much shorter. Hemodialysis with the NxStage machine is similar to short daily hemodialysis (SDHD) with traditional dialysis equipment, but is done for slightly longer than standard SDHD, and at a far lower dialysate flow rate. In order to provide adequate solute clearance at a much slower dialysate flow rate (and less total dialysate volume), dialysate need to be highly saturated (see slides 7-9)


SDHD - Traditional technology.

• Clearance• Qb 400; Qd 600 • Typical spKt/V ~ 0.8

• Time on therapy• 2 hours – adjust to achieve target clearance

• Potassium• Adjust according to blood test results

• Bicarbonate• Adjust according to blood test results

• Calcium• Adjust according to blood test results

• Heparin• Bolus 1500-3000 units

5 Approach is exactly the same as in-center HD

Presenter

Presentation Notes

The approach to prescriptions for home hemodialysis using traditional dialysis equipment is exactly the same as in-center HD. The only difference is time is shorter and heparin can be given as a bolus. Currently only traditional dialysis machine approved for use in the home is the Fresenius 2008 K@home machine. Traditional dialysis machine also requires water treatment equipment (e.g. portable R.O.). Plumbing and electrical modifications to the home is required.


New Technology

Technology should adapt to patient’s needs.

Patient should not have to adapt to technology.

For patients to embrace HHD, machines should be:

• Easy and simple to use

• Small and unobtrusive in the home

• Minimize storage space requirement

• Reliable

• Relatively maintenance free

• Portable

• Affordable

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NxStage machine is the only “new technology” currently available in the U.S. and majority of home HD patients utilize this machine. It has become synonymous with SDHD. However to avoid any possible perception of bias, will refer to NxStage as the “Low dialysate volume approach (LDVA)”


Comparing PD, LDVA and CHD:

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Modality PD LDVA CHD

Dialysate Volume (L) 8-18 15-35 140

Dialysate Urea Saturation High (60-100%) High (85-90%) Low (~30-40%)

To change saturation Change DT Change FF n/a

Prescription variables that increase Kt/V:

-Change dialysate volume ‘ ‘ n/a

-Change dialysis saturation ‘ DT “ FF n/a

-Change Qb and Qd n/a n/a ‘ one or both

-Dialyzer n/a n/a ‘ KoA

CHD = Conventional HDDT = Dwell timeFF = Flow Fraction = Qd/Qb

Qd = Dialysate flow rateQb = Blood flow rateKoA = Mass transfer area coefficient

Presenter

Presentation Notes

LDVA is very different than conventional HD (CHD). LDVA can be applied to any hemodialysis machine but is a requirement for NxStage. In a way it is more similar to PD than traditional HD: PD is a low volume therapy. PD dialysate becomes highly saturated with urea compared to the achieved saturation of dialysate during in-center HD. In the LDVA dialysate is also highly saturated In PD, as with the LDVA, larger patients have larger volume of distribution of urea and therefore need more dialysate fluid to achieve target Kt/V. In PD we can adjust the saturation of PD fluid (D/Purea) by changing the dwell time. In LVDA we adjust saturation of dialysate by changing the “Flow Fraction (FF) = Qd/Qb”. Though alterations in Qb and Qd will change FF (see slides 8-11), it is simpler to think in terms of just FF (until prescriber is comfortable with basic concepts!) In conventional hemodialysis in order to adjust Kt/V we focus on blood flow, dialysate flow, dialyzer and time of therapy. We do not focus on saturation of dialysate fluid, or volume of dialysate fluid


FF and dialysate saturation:

• The LDVA is based on the principle that dialysate fluid is nearly completely saturated with urea if the dialysate flow rate is much slower than the blood flow rate. Consider an extreme example of dialysate trickling through a dialyzer and a huge amount of blood flows across the other side of dialyzer membrane. The huge amount of urea diffusing across the dialyzer will completely saturate the trickling dialysate. As dialysate flow increases relative to blood flow saturation will decrease (though urea clearance increases).

• LDVA results in very efficient use of dialysate.

• The term Flow Fraction (FF) defines the relationship between dialysate flow (Qd) and blood flow (Qb) and is equal to Qd/Qb.

• At low flow fraction Qd relative to Qb is low and dialysate saturation is high.

• At high flow fraction Qd relative to Qb is high and dialysate saturation is lower.

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0.50

Improving Efficiency by Decreasing Flow Fraction: Qd/Qb

0.10 0.400.0 0.20 0.30

90%

95%

100%

85%

80%

Flow Fraction

Dia

lysa

te

Sat

ura

tio

n

Data reproduced with permission from: NxStage Medical, Inc. Copyright © 2012.

Urea

Creatinine

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Presenter

Presentation Notes

This graph shows the approximate relationship between FF and percent saturation. Commonly, prescribers refer to FF as a percent (e.g. “40”) or a fraction (e.g. “0.4”). For simplicity X axis is labelled as fraction. Choose a flow fraction that will produce desired dialysate saturation. For example: FF Saturation (%) 0.2 95 0.3 93 0.4 90 0.5 85 Typical prescribed flow fraction for LDVA is between 0.4 and 0.5


LDVA Prescription, FF, and Treatment Time

• Order appropriate amount of dialysate volume.

• Order flow fraction (which determines dialysate saturation). It is programmed into machine.

• Order Qb. This is not programmed but entered by patient.

• Qd is NOT ordered but is determined by the machine according to the formula Qd = (FF)(Qb) or FF = Qd/Qb.

• Time of therapy is NOT ordered. Time of therapy is a dependent variable. It is dependent on the amount of dialysate prescribed and the Qd that is determined by the machine. The Qd is determined by the flow fraction and the prevailing Qb: Qd = (FF)(Qb).

• The maximum flow fraction is fixed by your order and therefore a minimum saturation is fixed. This guarantees the dialysate fluid will achieve target saturation.

• Achieving target saturation guarantees target spKt/V is achieved at end of treatment.

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Prescription, FF, and Treatment Time

• FF = Qd/Qb

• Qd = (FF)(Qb)

• Since FF is fixed by your order, at a constant Qb, Qd is constant. If we prescribe more dialysate volume then time of therapy will INCREASE.

• Since FF is fixed by your order, if there is a decrease in Qb then Qdwill decrease and time of therapy will INCREASE.

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Exercise: Estimate an initial LDVA prescription

• Patient

• 90 Kg male

• 5 days per week therapy, SDHD

• Approximate volume distribution of urea = 45 L

• Solution:

• Target std Kt/V = 2.0; target per treatment spKt/V = 0.6 (slide 3)

• Then target Kt = (Kt/V)(V) = (0.6)(45) = 27 L. This means that we need 27 L of 100% saturated dialysate fluid to achieve a target Kt/V of 0.6.

• If we choose to use 30L of dialysate then then the fluid needs to be about 90% saturated to be equivalent to 27 L of 100% saturated fluid

• (0.9)(30 L) = 27 L

• FF 0.4 will yield saturation of about 90% (slide 9)

• Our prescription will be 30L dialysate at FF 0.4. If Qb is 400 ml/min then Qd will be 160 ml/min and time on therapy will be about 188 minutes (30,000 mL / 160 ml/min).

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Presenter

Presentation Notes

This exercise is just a math problem that applies principles of target spKt/V to achieve target std Kt/V, and FF as a determinate of dialysate saturation. However, we do not measure Kt/V in this manner. We calculate spKt/V from URR, and then calculate std Kt/V from spKt/V. A much simpler approach to therapy prescription is on the next slide!


NxStage LDVA Prescriptions

• Actually, is much easier than that. For SDHD: Pick a reasonable dialysate volume according to patient weight and a reasonable flow fraction. Then measure spKt/V (URR) and calculate std Kt/V. If you do not achieve target std Kt/V change flow fraction or dialysate volume or both and measure spKt/V and calculate std Kt/V again.

• Example of reasonable initial prescriptions for 5 day per week therapy:

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Dialysate volumeSmall: (<70 kg) 20 litersMedium: (70-85 kg) 25 litersLarge: (85-100 kg) 30 liters>100 kg 35 liters

Flow fractionAbout 0.40 (40%)

Presenter

Presentation Notes

Calculation of spKt/V from URR and std Kt/V from sp Kt/V is done by computer program and is typically automatically reported with dialysis labs.


Examine variables that determine Kt/V

Kt/Vurea = (D/Purea)(Dialysate drain volume/day)(7 days)

VDUrea (TBW)

(D/Purea)(Dialysate drain volume)

VDUrea (TBW)

D/Purea is percent saturation and is determined by flow fraction

Peritoneal Dialysis

NxStage =(per tx Kt/Vurea)

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Modifiable parameters

Fixed

Presenter

Presentation Notes

To manipulate the prescription to achieve best results it helps to understand the therapy! It is easiest to think of LDVA Kt/V similar to PD Kt/V�Depicted are formulas for PD Kt/V and then an analogous formula for HD Kt/V



VDUrea (TBW)

• D/Purea is percent saturation and is determined by flow fraction

• Increase saturation

• To change percent saturation change flow fraction

• Lower flow fraction (slower dialysate flow) results in higher dialysate saturation.

OR

• Increase dialysate volume

Per Treatment Kt/Vurea =

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Modifiable parameters

Fixed

Adjust prescription when Kt/V is below target:


Manipulate variables to achieve target Kt/V


VDUrea (TBW)

D/Purea is percent saturation and is determined by flow fraction

Per Treatment Kt/Vurea =

To increase Kt/V we can:1) Increase percent saturation (decrease FF)2) Increase dialysate volumeBOTH strategies will increase time on dialysis

BUT if we generously increase dialysate volume, we could increase FF (increase Qd and decrease percent saturation) and still achieve target Kt/V without increase in time per treatment.

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Nocturnal Hemodialysis: LDVA

• Target spKt/V is determined the same way as SDHD

• Approach to FF is different because we want to tailor treatment time to patients sleep time

• For example: 85 Kg patient

• Patients sleeps for 8 hours (480 minutes)

• Patient needs 30 liters of dialysate fluid (slide 13)

• Dialysate flow rate should be about 30,000 ml/480 minutes = 63 ml/min

• If Qb is 250 mL/min then FF = 63/250 = 0.25.

• At FF 0.25 dialysate will be HIGHLY saturated.

• This calculation does not take into account machine re-calibration time which occurs repeatedly during therapy and adds time to therapy.

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Dialysate Options

• Traditional dialysis equipment

• Same options as in-center HD

• NxStage (LDVA)

• Limited dialysate options (similar to PD!)

• 5 liter sterile bags

• Batch (ultrapure) dialysate production by PureFlow system

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NxStage Fluids

Sterile Bags PureFlow

Higher Buffer Lower Buffer High Buffer Lower Buffer

Lactate 45 40 45 40

Na+ (meq/L) 140 140 140 140

K+ (meg/L) 1 or 2 1 1 or 2 1

Ca2+ (meq/L) 3 3 3 3

Mg2+ (meq/L) 1 1 1 1

Cl- (meq/L) 100 105 100 105

Dextrose (mg/dL)

100 100 100 100

40, 50 or 60 liter sacks5 Liter bags

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Presenter

Presentation Notes

Lactate, when metabolized in liver, generates bicarbonate (1:1 ratio). NxStage dialysate fluids are not approved for use in patient with liver disease because of lactate. However, lactate is the bicarbonate source in PD fluids and PD has been used in patients with cirrhosis. Sodium is only available as 140 meq/L. Potassium is 1.0 meq/L but there is a 2.0 meq/L option for 45 meq lactate bags and the 45 meq/L lactate, 60 Liter sack. Patients do not become hypokalemic on 1.0 meq/L because low volume limits potassium removal (peritoneal dialysate fluid potassium concentration is 0 meq/L). NxStage calcium only available in 3.0 meq/L but there does not appear to be an increased incidence of hypercalcemia (King, R and Glickman, JD. Electrolyte Levels and Management in Frequent Home Dialysis. Semin Dialysis, 23:571-574, 2010). Manufacturer (NxStage) might change dialysate options in the future.


Fluid Removal

• The approach to fluid removal is exactly the same as in-center conventional HD

• Ultrafiltration rates should be low to avoid myocardial stunning and intradialytic hypotension.

• Though there is no literature regarding safe UF rates in SDHD it is reasonable to extrapolate from CHD and limit UF to 10-13 ml/kg/hr.

• However, intradialytic hypotension at home is UNACCEPTABLE and patients must be educated on methods to avoid excessive UF as well as proper monitoring and interventions for intradialytic hypotension.

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Anticoagulation

• The NxStage machine does not have an internal heparin pump.

• For SDHD treatment time is short enough to use bolus heparin (approximately 1000-2000 units at initiation of treatment).

• For extended treatment time maintenance heparin requires an additional external heparin pump. Heparin dose is typically 1000-2000 units initial bolus followed by 500-1500 units per hour maintenance dosing.

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New Technologies In The Future

• There are at least 2 new HHD machines currently in clinical trial

• The machines were developed specifically for HHD

• Each machine has different technology to simplify home hemodialysis

• One machine utilizes “sorbent” technology that regenerates dialysate from just 6 liters of tap water

• Nephrologists will need to learn about prescriptions for new machines as they become available.

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Documents

ASN DIALYSIS ADVISORY GROUP...This image cannot currently be displayed. Goals For A Successful HHD Prescription • SOLUTE REMOVAL • Small solute target: std Kt/V > 2.0 • Achieved