Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
152
Wiparat Srisuwan, M.N.S.*, Saranya Charoensri, R.N.*, Kanittha Jantarakana, M.Ed.*, awee Chanchairujira,
M.D.**
*Nursing Department, **Division of Nephrology, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700,
ailand.
Increasing Dialysate Flow Rate over 500 ml/min for
Reused High-Flux Dialyzers do not Increase
Delivered Dialysis Dose: A Prospective Randomized
Cross Over Study
ABSTRACT
Objective: e primary objectives were: 1) to study the impact of Qd (500 vs 800 ml/min) on the delivered dose by
reused dialyzers, and 2) to determine dialysis eciency of a dialyzer reused 15 times.
Materials and Methods: A prospective randomized-controlled crossover study was conducted in 42 thrice-weekly
hemodialysis (HD) patients (630 HD sessions in each Qd). Delivered doses at both Qds were assessed by single-pool
Kt/V (spKt/V), equilibrated Kt/V (eKt/V) and online clearance monitoring Kt/V (Kt/V
OCM
), measured at mid-week
HD session using a new dialyzer and then again at every mid-week HD session.
Results: Although the spKt/V in HD sessions using new dialyzers at Qd of 500 ml/min was slightly lower than
spKt/V at Qd of 800 ml/min (2.19±0.08 vs. 2.34±0.08, respectively, P=0.04), when accounting for urea rebound as
assessed by eKt/V and Kt/V
OCM
, there was no signicant dierence. e average delivered doses in dialyzers reused
15 times, with the mean average of spKt/V, eKt/V and Kt/V
OCM
at Qd 500 ml/min, were not signicantly inferior to
the delivered doses at Qd 800 ml/min. Reusing a dialyzer 15 times did not decrease dialysis eciency and delivered
doses in all HD sessions reached spKt/V >1.4.
Conclusion: Increasing Qd over 500 ml/min for modern dialyzers does not signicantly increase delivered dose of
dialysis. Dialyzer reuse does not aect dialysis eciency and provides adequate dialysis therapy.
Keywords: Dialysate ow rate; hemodialysis adequacy; reused dialyzer; delivered Kt/V; online Kt/V; equilibrated
Kt/V (Siriraj Med J 2022; 74: 152-160)
Corresponding author: awee Chanchairujira
E-mail: thaweechan@hotmail.com
Received 31 September 2021 Revised 7 January 2022 Accepted 8 January 2022
ORCID ID: https://orcid.org/0000-0001-7692-2560
http://dx.doi.org/10.33192/Smj.2022.19
All material is licensed under terms of
the Creative Commons Attribution 4.0
International (CC-BY-NC-ND 4.0)
license unless otherwise stated.
INTRODUCTION
An adequate hemodialysis dose delivery is an
important and independent predictor of morbidity
and all-cause mortality in maintenance hemodialysis
(HD) patients.
1
Current clinical practice guidelines for
hemodialysis adequacy recommend a delivered single-
pool Kt/V (spKt/V) of at least 1.2 per HD session (for
3-time-weekly HD patients without signicant residual
renal function), and higher doses of up to 1.4 in females
and patients with high comorbidities.
1,2
e delivered
Srisuwan et al.
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
153
Original Article
SMJ
dose of HD depends on dialyzer mass transfer-area
coecient (KoA), HD treatment time, and operating
parameters, especially blood ow rate (Qb) and dialysate
ow rate (Qd).
3
High-eciency dialysis requires dialyzer
with high KoA, Qb > 300 ml/min and Qd ≥ 500 ml/min.
Increasing Qd from 500 ml/min to 800 ml/min has been
recommended to maximize dialysis eciency in high-
eciency HD. Previous studies
4-6
in early generation
dialyzers showed that increasing Qd from 500 ml/min to
800 ml/min alter the dialyzer KoA and results in a larger
increase in urea clearance than the predicted assuming
a constant KoA, which was explained by a better ow
distribution through the dialysate compartment and
a decrease in dialysate-side boundary layer resistance.
Recent studies
7-10
of newer dialyzers with improved
dialysate ow distribution designs (such as hollow ber
undulations, spacer yarns, and changes in ber packing
density) have been accompanied by an increase in urea
clearance of the dialyzer, and revealed that dialysate
ow rate beyond 500 - 600 ml/min does not signicantly
increase delivered Kt/V. However, these studies were
performed in single-use dialyzers.
In chronic hemodialysis, reuse of dialyzers has
been widely practiced in developing countries, including
ailand. In our hemodialysis unit, patients who were
treated with high-eciency high-ux dialysis usually
increasing Qd to 800 ml/min in order to maximize
the dialysis dose and the dialyzer was reused 15 times.
ere is limited data on the eect of Qd in high-ux
high-eciency dialysis with a reused dialyzer related to
delivered dose and hemodialysis adequacy. Increasing
the dialysate ow rates results in a higher dialysis cost,
require more water treatment, and leads to a higher risk
of exposure to dialysis water impurities. e objectives
of this study were to: 1) evaluate the eect of Qd of 800
ml/min and 500 ml/min on delivered dialysis dose in
high-eciency high-ux dialysis patients who used a
reused dialyzer; 2) to determine dialysis eciency and
HD adequacy of a reused dialyzer.
MATERIALS AND METHODS
Study design
We performed a single-center prospective randomized-
controlled crossover study in maintenance HD patients
conducted at Siriraj Hospital, Mahidol University, ailand
between June 2018 - April 2020. Inclusion criteria for
the study were age above 18, 4-hour three time weekly
high-ux dialysis with a stable spKt/V (±5%) for at least
two months, and the reuse of a dialyzer. e exclusion
criteria were pregnancy, hepatitis B virus infection and
being seropositive for HIV.
Before the intervention in each patient, bolus dose
and maintenance dose of heparin were adjusted according
to activated partial thromboplastin time (aPTT) level
(at baseline, 3, 60, 180 and 240 minutes) to maintain
a ratio of 1.8-2.5 for the duration of HD and at least
1.4 at the end of dialysis to prevent dialyzer clots and
achieve reuse. Automatic dialyzer reprocessing machine
(Meditop KIDNY- KLEEN®) was used to reprocess
dialyzers and disinfected with peracetic acid, and measure
blood compartment volume or total cell volume (TCV)
of reused dialyzers. Percentage of TCV (%TCV) of a
reused dialyzer was dened as the percentage of blood
compartment volume measured by automatic dialyzer
reprocessing machine divided by the priming volume value
of the new dialyzer that provided by the manufacturer
(Supplement Table 1). Reused dialyzers were discarded
if its TCV less than 80% of baseline value or if it failed
a leak test.
Patients were randomly assigned (using online soware
www.randomization.com) to be dialyzed according to an
AB or BA schedule, where A represents 15 consecutive
dialysis treatments with a Qd of 800 ml/min, and B
represents 15 consecutive dialysis treatments with a Qd
of 500 ml/min. e blood ow rate and dialyzer were
kept constant for a given patient. e intervention of A
and B began during a mid-week dialysis session with a
new dialyzer followed by sessions with a reused dialyzer
for a total of 15 times. e delivered dialysis dose was
measured (during both A and B) at mid-week HD sessions
with a new dialyzer and again at every mid-week HD
session corresponding to the reused dialyzer no. 4, 7, 10,
13, and 15 (total of six measurements in each dialyzer).
e delivered doses of dialysis were assessed by spKt/V
(the Daugirdas second generation equation), equilibrated
Kt/V (eKt/V) estimated by the rate equation
11
, and online
clearance monitoring Kt/V (Kt/V
OCM
).
12
Kt/V
OCM
was
calculated by serial measurements of ionic dialysance
of sodium (as a surrogate for eective urea clearance)
made throughout HD treatment by using HD machines
equipped with an online conductivity monitor and soware
dose-calculation tool DCTool (Fresenius Medical Care,
Germany). Volume distribution of urea (V) will be
calculated by the system from the weight, height, age
and sex using the formula developed by Watson.
Data collection
Baseline data included patient’s age, sex, height,
body weight, dialysis vintage, comorbidities, medical
history, vascular access, and HD treatment parameters,
which consist of dialysis dose, Qb, Qd, post-HD body
weight (W), ultraltration (UF), total processed blood
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
154
Supplement TABLE 1. Summary of dialyzer specications
#
Hdf 100s Hf 80s EL210HR EL190HR FB190U
Surface area (m
2
) 2.3 1.8 2.1 1.9 1.9
Priming volume (ml) 138 110 130 115 115
Ultraltration coefcient (Kuf) (ml/h/mmHg) 60 55 82 76 37.70
Dialyzer KoA
urea
(ml/min) 1,167 805 1,976 1,171 1,367
Inulin clearance (ml/min)* 145 120 145 132 N/A
Myoglobin clearance (ml/min)* N/A N/A 104 101 47
Membrane component Polysulfone Polysulfone Polynephron Polynephron Cellulose
triacetate
Number of patients n, (%) 15 (35.70%) 3 (7.10%) 22 (52.40%) 1 (2.40%) 1 (2.40%)
* Blood ow rate 300 ml/min, Dialysate ow rate 500 ml/min
# Data from the manufacturer’s dialyzer specication sheets
Calculations
Single-pool delivered Kt/V (spKt/V) was calculated using the Daugirdas second generation equation** as follows: spKt/V = -Ln(R-
0.008×t) + (4-3.5×R) × UF/W, where Ln is the natural logarithm, R is the post-dialysis/pre-dialysis blood urea nitrogen ratio, t is dialysis
time (in hours), UF is ultraltration volume (in liters), and W is the patient’s post-dialysis body weight (Kg).
Equilibrated Kt/V (eKt/V) was calculated by adjusting the spKt/V for postdialysis urea rebound using the rate equation described
by Daugirdas and Schneditz as follows: eKt/V = spKt/V – [0.6 x(spKt/V)/t] + 0.03 (for arteriovenous access) and eKt/V = spKt/V –
[0.47×(spKt/V)/t] + 0.02 (for venous catheters), where t represents the duration of dialysis in hours.
** Daugirda JT. Second generation logarithmic estimates of single-pool variable volume Kt/V: An analysis of error. J Am Soc Nephrol 1993;
4:1205-13.
volume (TBV), eective dialysis time, heparin dosage,
type of dialyzer and number of dialyzer reuse with %TCV.
Patients gave written informed consent to participate in
this study as approved by the Human Research Protection
Unit, Faculty of Medicine Siriraj Hospital, Mahidol
University, ailand.
Exposures and outcomes
The primary outcome was differences between
delivered spKt/V, eKt/V and Kt/V
OCM
at two dierent
dialysate ow rates. Secondary outcomes were dierences
between eKt/V and Kt/V
OCM
, and how the number of
times a dialyzer was related to dialyzer urea clearance
ecacy and HD adequacy. In this study, the hemodialysis
adequacy threshold was set to delivered spKt/V > 1.4,
considering high proportion of comorbidities and females
(43%) in the patient population.
Statistics
e data are reported as mean ± standard deviation
(SD) or median (minimum-maximum), depending on
the distribution analysis. A two-sided p value of <0.05
was considered as signicant. e primary outcome was
non-inferiority of delivered dialysis dose at two Qds in
rst use and reused dialyzer, which were assessed by
ANOVA using NCSS program with signicance, α =
0.05 and non-inferiority margin of spKt/V = 0.25.
RESULTS
Forty-two HD patients were studied and a total of
1,260 HD sessions (630 HD sessions in each Qd) were
performed. e dialyzers used in this study were HdF100s
35.7%, HF80s 7.1%, EL210HR 52.4%, EL190HR 2.4%,
FB210U 2.4% and FB190U 2.4%. e characteristics
of the dialyzers were summarized in the Supplement
Table 1. Eighty-one percent of patients needed heparin
dose adjustments to achieve an appropriate aPTT level
throughout the HD sessions for prevent dialyzer clots
before the intervention. All dialyzers used in this study
were reused 15 times. e average %TCV in reused
dialyzers at both Qds were not signicantly dierent
(Qd 800 ml/min, %TCV 97.80±1.20% vs Qd 500 ml/
min, %TCV, 97.99±0.96%).
Srisuwan et al.
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
155
Original Article
SMJ
Baseline patient characteristics
e patient’s baseline characteristics are summarized
in Table 1. e mean age of 42 patients was 66.3±15.3
years (range 29.2 - 84.4 years) and 57.1% were men.
e eect of dialysate ow rate on delivered spKt/V
in reused dialyzers
e mean spKt/V in the HD sessions using new
dialyzers at Qd of 500 ml/min was slightly less than
the mean spKt/V at Qd of 800 ml/min (2.19± 0.08 vs.
2.34± 0.08, respectively, p=0.04) (Table 2). In the HD
sessions of reused dialyzers no. 4, 7, 10 and 13, the mean
spKt/V at Qd 500 ml/min were signicantly inferior to
spKt/V at Qd 800 ml/min, whereas, the mean spKt/V
in reused dialyzers no. 15 at both Qds was not dierent.
However, the magnitude of dierences in spKt/V was
not clinically meaningful. e mean average spKt/V of
dialyzers reused 15 times was calculated from the average
of spKt/V of the new dialyzers and reused dialyzers (total
of six measurements of spKt/V in each dialyzer). e
mean average spKt/V of the reused dialyzers aer 15
times at Qd 500 ml/min was not signicantly inferior
to spKt/V at Qd 800 ml/min (2.21±0.07 vs 2.31±0.07,
respectively, p<0.01). All measurements of the delivered
dose achieved hemodialysis adequacy thresholds of
spKt/V > 1.4 at both dialysate ow rates.
e eect of dialysate ow rate on eKt/V
e mean eKt/V in the HD sessions of new dialyzers,
and reused dialyzers no. 4, 7, and 13 at Qd of 500 ml/min
TABLE 1. Baseline characteristics of study population (n = 42 patients).
Parameters
Age, years 66.3±15.3
Male sex, n (%) 24 (57.10)
Mean post-HD body weight, Kg 58.85±11.82
Comorbid diseases, n (%)
Hypertension 39 (92.9)
Diabetes 16 (38.1)
Atherosclerotic heart disease 16 (38.1)
Polycystic kidney disease 2 (4.8)
Miscellaneous (hyperlipidemia (3)/chronic 7 (16.7)
glomerulonephritis (1)/gout (1) /benign prostate
hypertrophy (1)/ malignancy (1)
Dialysis vintage, months 106.2±68.4
Vascular access, n (%)
Arteriovenous stula 17 (40.48)
Arteriovenous graft 6 (14.29)
Permanent dual lumen catheter 19 (45.23)
Blood ow rate, n (%)
300/350/400 ml/min 1 (2.4) / 11 (26.2) / 30 (71.4)
Heparin dose, units/session
Total 4,431±3,712
Loading dose 1,681±1,761
Maintenance dose 2,750±1,944
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
156
TABLE 2. Mean delivered spKt/V at dialysate ow rate of 800 and 500 ml/min.
Dialyzer Mean spKt/V Mean 95%CI P value
Reuse No. Qd 800 ml/min Qd 500 ml/min difference Lower Upper Non-Inferiority
New 2.34±0.08 2.19±0.08 0.15 -0.07 0.37 0.04
4 2.35±0.07 2.22±0.07 0.13 -0.07 0.33 0.22
7 2.35±0.07 2.21±0.07 0.14 -0.07 0.35 0.29
10 2.30±0.08 2.24±0.08 0.07 -0.17 0.30 0.13
13 2.29±0.07 2.19±0.07 0.10 -0.10 0.30 0.14
15 2.23±0.07 2.23±0.07 0.00 -0.21 0.21 0.02
Average 2.31±0.07 2.21±0.07 0.10 0.05 0.14 <0.01
were not signicantly inferior to the mean eKt/V at Qd of
800 ml/min (Table 3). In reused dialyzers no.10 and 15, the
mean eKt/V at Qd 500 ml/min were signicantly inferior
to eKt/V at Qd 800 ml/min. However, the magnitude
of dierence of eKt/V may not be clinically signicant.
e mean average eKt/V of dialyzers reused 15 times at
Qd 500 ml/min was not signicantly inferior to eKt/V
at Qd 800 ml/min (1.93±0.27 vs 2.03±0.29, respectively,
p<0.01).
e eect of dialysate ow rate on Kt/V
OCM
e mean Kt/V
OCM
at Qd of 500 ml/min in HD
sessions using new dialyzers and reused dialyzers were
not signicantly inferior to Kt/V
OCM
at Qd of 800 ml/min
(Table 4). e mean average Kt/V
OCM
of dialyzers reused
15 times at Qd 500 ml/min was also not signicantly
inferior to Kt/V
OCM
at Qd 800 ml/min (1.85±0.04 vs
1.98±0.05, respectively, p<0.01).
Comparison between eKt/V and Kt/V
OCM
e mean average of Kt/V
OCM
at both Qds were
signicantly lower than the mean average eKt/V (Table
5). However, the magnitude of dierence between Kt/
V
OCM
and eKt/V may not be clinically signicant. e
Kt/V
OCM
was highly correlated with eKt/V at the both
Qds, with r = 0.91 at Qd 800 ml/min (p<0.01), and r =
0.87 at Qd 500 ml/min (p<0.01).
e total processed blood volume and eective time
in HD sessions of new dialyzers and reused dialyzers were
not signicantly dierent (Table 6). e average eective
TABLE 3. Mean eKt/V at dialysate ow rate of 800 and 500 ml/min.
Dialyzer Mean eKt/V Mean of 95%CI P value
reuse No. Qd 800 ml/min Qd 500 ml/min difference Lower Upper Non-Inferiority
New 2.03±0.35 1.92±0.30 0.10 0.04 0.17 <0.01
4 2.04±0.30 1.95±0.29 0.09 0.03 0.16 <0.01
7 2.00±0.34 1.97±0.31 0.03 -0.06 0.11 <0.01
10 2.08±0.54 1.94±0.31 0.14 0.01 0.27 0.11
13 1.98±0.29 1.93±0.30 0.06 -0.01 0.12 <0.01
15 2.04±0.36 1.90±0.43 0.15 0.02 0.26 0.09
Average 2.03±0.29 1.93±0.27 0.10 -0.12 -0.03 <0.01
Srisuwan et al.
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
157
Original Article
SMJ
TABLE 4. Online clearance Kt/V at dialysate ow rate of 800 and 500 ml/min.
TABLE 5. Comparison of Kt/V
OCM
and eKt/V at dialysate ow rate of 800 and 500 ml/min.
Dialyzer Mean Kt/V
OCM
Mean of 95%CI P value
Reuse No. Qd 800 ml/min Qd 500 ml/min difference Lower Upper Non-Inferiority
New 1.99±0.32 1.87±0.29 0.11 0.06 0.17 <0.01
4 1.99±0.32 1.85±0.28 0.14 0.08 0.19 <0.01
7 1.99±0.34 1.87±0.29 0.12 0.05 0.18 <0.01
10 1.93±0.34 1.87±0.29 0.06 0.00 0.12 0.05
13 1.96±0.32 1.82±0.30 0.14 0.07 0.20 <0.01
15 2.00±0.40 1.83±0.29 0.17 0.07 0.27 <0.01
Average 1.98±0.05 1.85±0.04 0.13 0.06 0.17 <0.01
Dialyzer Kt/V
OCM
eKt/V Mean 95% CI P value
reuse No. difference Lower Upper Inferiority
Qd 800 ml/min
New 1.99±0.32 2.03±0.35 -0.04 -0.11 0.03 <0.01
4 1.99±0.32 2.04±0.30 -0.05 -0.12 0.03 <0.01
7 1.99±0.34 2.00±0.34 -0.02 -0.08 0.04 0.61
10 1.93±0.34 2.08±0.54 -0.15 -0.28 -0.02 0.03
13 1.96±0.32 1.98±0.29 -0.03 -0.10 0.05 0.48
15 2.00±0.40 2.04±0.36 -0.04 -0.16 0.08 0.49
Average 1.98±0.30 2.03±0.05 -0.05 -0.00 0.11 <0.01
Qd 500 ml/min
New 1.87±0.29 1.92±0.30 -0.05 -0.12 -0.02 <0.01
4 1.85±0.28 1.95±0.29 -0.09 -0.17 -0.02 <0.01
7 1.87±0.29 1.97±0.31 -0.10 -0.18 -0.02 <0.01
10 1.87±0.29 1.94±0.31 -0.07 -0.13 -0.00 0.04
13 1.82±0.30 1.93±0.30 -0.11 -0.19 -0.03 <0.01
15 1.83±0.29 1.90±0.43 -0.07 0.18 0.05 <0.01
Average 1.85±0.30 1.93±0.04 -0.08 0.02 0.14 <0.01
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
158
TABLE 6. Total processed blood volume (TBV), eective dialysis time, % total cell volume (TCV) related to Kt/V
OCM
and eKt/V at Qd 800 and 500 ml/min.
Qd 800 New Reused Dialyzer P value
ml/min Dialyzer no. 4 no. 7 no. 10 no. 13 no. 15
TBV (L) 90.21±6.57 89.95±6.21 89.98±6.91 89.63±6.23 89.53±6.65 89.90±5.96 0.89
Time* 3.52±0.08 3.52±0.03 3.51±0.04 3.53±0.08 3.51±0.03 3.52±0.09 0.76
%TCV 100±0 98.63±2.59 98.46±2.54 97.42±3.61 96.62±4.36 96.49±5.04 0.00
Kt/V
OCM
1.99±0.32 1.99±0.32 1.99±0.34 1.93±0.34 1.96±0.32 2.00±0.40 0.53
eKt/V 2.03±0.35 2.04±0.30 2.00±0.34 2.08±0.54 1.98±0.29 2.04±0.36 0.23
Qd 500 New Reused Dialyzer P value
ml/min Dialyzer no. 4 no. 7 no. 10 no. 13 no. 15
TBV (L) 90.66±6.44 89.67±6.50 89.97±7.24 90.59±6.60 90.08±6.00 89.51±7.12 0.33
Time* 3.54±0.11 3.51±0.05 3.53±0.08 3.51±0.08 3.54±0.11 3.51±0.04 0.07
%TCV 100±0 99.39±1.56 98.29±3.25 98.15±2.87 97.62±4.09 96.42±5.23 0.00
Kt/V
OCM
1.87±0.29 1.85±0.28 1.87±0.29 1.87±0.29 1.82±0.30 1.83±0.29 0.19
eKt/V 1.92±0.30 1.95±0.29 1.98±0.31 1.94±0.31 1.93±0.30 1.90±0.43 0.72
% TCV dened as % of blood compartment volume of a reused dialyzer divided by the priming volume value of new dialyzer provided by
the manufacturer.
*Eective time (hr.min)
Srisuwan et al.
treatment time was 3 hours 52 minutes. e TCV remained
above 80% of the baseline value for dialyzers reused up
to 15 times, and the average decrease in %TCV was only
1.4-3.5%. e reused dialyzers did not alter ecacy of
hemodialysis. e eKt/V and Kt/V
OCM
measured in
HD sessions using new dialyzers and reused dialyzers
were not signicantly dierent at both Qds (Table 6).
DISCUSSION
We found little improvement in delivered dialysis
dose as assessed by spKt/V, eKt/V and Kt/V
OCM
while
increasing Qd from 500 ml/min to 800 ml/min. Although
the mean spKt/V in HD sessions using new dialyzers
at Qd of 500 ml/min was slightly lower than spKt/V at
Qd of 800 ml/min (2.19±0.08 vs. 2.34±0.08, P =0.04),
when accounting for urea rebound by assessing eKt/V
and Kt/V
OCM
, there was no signicant dierence at both
Qds (eKt/V 1.93±0.27 vs. 2.03±0.29; Kt/V
OCM
1.85±0.04
vs.1.98±0.05 at Qd 500 and Qd 800 ml/min, respectively).
When comparing the average delivered dialysis dose of
dialyzers reused 15 times between Qd of 500 ml/min and
800 ml/min, the mean average spKt/V was not signicantly
dierent (2.21±0.07 vs 2.31±0.07), as well as the mean
average eKt/V and Kt/V
OCM
. A study by Bhiman JP,
et al
10
showed that the urea KoA was independent of Qd
in the range 500 ml/min to 800 ml/min for dialyzers with
enhanced dialysate ow distribution features, suggesting
that increasing the dialysate ow rate in this range would
not signicantly increase delivered Kt/V in modern
dialyzers. Consistent with our results, a study by Ward
RA, et al
8
in 42 patients comparing delivered Kt/V at
Qd of 600 and 800 ml/min with a median Qb of 450
ml/min showed that an increase in Qd beyond 600
ml/min for dialyzer with enhanced Qd distribution
does not oer extra benet in delivered spKt/V and Kt/
V
OCM
. A recent randomized crossover study
13
reported
that reducing the Qd from 500 ml/min to 400 ml/min
in small patients (body weight < 65 kg) had no impact
on Kt/V, interdialytic weight gain, blood pressure or
electrolyte disturbance.
The equilibrated Kt/V, which accounts for the
postdialysis urea rebound, can be determined by eKt/V
estimated from rate equation or Kt/V
OCM
by ionic dialysance
method.
14
Although Kt/V
OCM
was slightly lower than
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
159
Original Article
SMJ
eKt/V, but the magnitude of dierence did not appear to
be clinically meaningful, and it is highly correlated with
eKt/V. Our results showed that Kt/V
OCM
is a practical
instrument and the easiest method to use to monitor
delivered dialysis doses in each HD treatment, and help
maintain recommended HD adequacy, especially in
patients using reused dialyzers.
We found that reused dialyzers did not alter ecacy
of hemodialysis and the delivered dose in all HD sessions
at both Qds reached the HD adequacy thresholds of
spKt/V > 1.4. Our results are consistent with Cheung
AK’s study
15
which showed that urea clearance decreased
only slightly in reused dialyzers (approximately 1 to
2% per 10 reuses). A study by Ousseph et al
16
showed
that both high-ux cellulosic and high-ux polysulfone
dialyzers maintained their Kt/V at the 12
th
and 15
th
use, respectively, when dialyzers were reprocessed with
Renalin and %TCV above 80% of the original value. In our
study, 81% of patients needed heparin dose adjustment
to achieve adequate aPTT level throughout HD session,
and this resulted in a high residual TCV (mean %TCV
> 96%) in dialyzers reused up to 15 times. e delivered
dialysis doses of dialyzers reused for 15 times were not
signicantly dierent from those of new dialyzers (Table
6). is may result from a high residual TCV as well
as the optimized eective HD time and adequate total
processed blood volume (Table 6).
In our study, 78% of high-eciency high-ux dialysis
patients were prescribed with large dialyzers (dialyzer
KoA > 1,160 ml/min with dialyzer surface area ≥ 2.1
m
2
and Kuf ≥ 60 ml/h/mmHg), which resulted in high
delivered Kt/V in the range of 2, especially in patients
with small body size (mean body weight 58.8 kg). High
Kuf of the dialyzer has the benet of a higher convective
clearance from back ltration, resulting in increased
middle molecule clearance. However, in the subgroup
of small body size patients with this high range of Kt/V,
dialysis prescription (especially Qd and Qb) should
be adjusted to a more appropriate Kt/V range to save
resources and preserve vascular access.
Our ndings have some practical applications. First,
the eect of reducing the Qd from 800 ml/min to 500 ml/
min on delivered dialysis doses of high-eciency dialysis
using modern dialyzers is minimal. e delivered dialysis
dose at Qd of 500 ml/min is preferred and this would result
in dialysate cost savings of around 72 liters per dialysis
session, less raw water consumption, and less the wear
and tear on water treatment systems.
17
Reducing in water
consumption will also decrease waste water production
and electrical consumption, and these have a positive
eect on the environment and carbon emissions, which
has been recently concerned in dialysis practice as green
nephrology and eco-dialysis.
17,18
However, increasing the
Qd beyond 500 ml/min should be considered in selected
patients who have not achieved HD adequacy despite
using an appropriate dialyzer KoA and optimized Qb,
especially in patients with high body weight. Second,
reusing a dialyzer up to 15 times does not aect dialysis
eciency and provides adequate dialysis therapy as long
as adequate anticoagulation throughout HD session
and high residual TCV are maintained. Dialyzer reuse
has some advantages, including less environmental
impact from limiting waste disposal from dialyzers and
packaging, and cost saving favoring in some developing
countries. However, reprocessing of dialyzers requires
additional personnel, disinfectants, room maintenance
for safety and sterilization, and oversight mechanism
of the dialyzer reuse standard. In developed countries,
single-use practice is now preferable to reuse of dialyzers
because the price of a high-ux dialyzer has recently gone
down, and the operational cost of dialyzer reprocessing
is rising, along with safety regulatory burden.
19,20
Our study had some limitations. It was a single-
center study. e Qbs used in this study were Qb of
400 ml/min in 71.4% of patients, and Qb of 350 ml/
min in 26% of patients. erefore, our results cannot be
extrapolated to dierent dialysis treatment conditions
that maximize Qb to >400 -450 ml/min. We did not
evaluate the eect of Qd on other solutes removal such
as protein-bound solutes or middle molecules, and the
eect of reused dialyzer on sieving coecient of middle
molecule. However, increasing Qd in the range from 500
ml/min to 800 ml/min would not have any signicant
eect on clearance of these solutes.
CONCLUSION
Our data suggest that increasing dialysate ow
rate beyond 500 ml/min for modern high-ux dialyzers
does not signicantly increase delivered dialysis dose.
e delivered dose at Qd of 500 ml/min is more cost-
eectiveness. Reuse of a dialyzer up to15 times does not
aect dialysis eciency and provides adequate dialysis
therapy.
ACKNOWLEDGMENTS
e authors give special thanks to Mr Suthipol
Udompunturak, Department of Research Development,
Faculty of Medicine Siriraj Hospital, Mahidol University
for statistical analysis. is study was supported by the
Siriraj Research Development Fund (Managed by Routine
to Research: R2R).
Volume 74, No.3: 2022 Siriraj Medical Journal
https://he02.tci-thaijo.org/index.php/sirirajmedj/index
160
REFERENCES
1. John Daugirdas TAD, Jula Inrig, Rajnish Mehrotra, Michael
V. Rocco, Rita Suri, Daniel E. Weiner, Jerey Berns. KDOQI
Clinical practice guideline for hemodialysis adequacy: 2015
update. Am J Kidney Dis 2015;66(5):884-930.
2. Ashby D, Borman N, Burton J, Richard C, Davenport A,
Farrington K, et al. Renal association clinical practice guideline
on hemodialysis. BMC Nephrology 2019; 20:379. doi: 10.1186/
s12882-019-1527-3.
3. Hootkins R. Lessons in dialysis, dialyzers, and dialysate. Dialysis
& Transplantation 2011; 40: 392-396
4. Leypoldt JK, Cheung AK, Agodoa LY, Daugirdas JT, Greene
T, Keshaviah PR. Hemodialyzer mass transfer-area coecients
for urea increase at high dialysate ow rates. e Hemodialysis
(HEMO) Study. Kidney Int 1997;51(6):2013-7.
5. Hauk M, Kuhlmann MK, Riegel W, Köhler H. In vivo eects
of dialysate ow rate on Kt/V in maintenance hemodialysis
patients. Am J Kid Dis 2000;35(1):105-11.
6. Ouseph R, Ward RA. Increasing dialysate ow rate increases
dialyzer urea mass transfer-area coecients during clinical
use. Am J Kidney Dis 2001; 37(2): 316-20.; 51(6): 2013-7
7. Hirano A, Kida S, Yamanoto K, Sakai K. Experimental evaluation
of ow and dialysis performance of hollow-ber dialyzers with
dierent packing densities. J Artif Organs 2012; 15:168-75.
8. Ward RA, Idoux JW, Hamdan H, Ouseph R, Depner TA,
Golper TA. Dialysate ow rate and delivered Kt/Vurea for
dialyzers with enhanced dialysate ow distribution. Clin J Am
Soc Nephrol 2011;6(9): 2235-9.
9. Albalate M, Pere-Garcia R, de Sequra P, Corchete E, Alcazar R,
Ortega M, et al. Is it useful to increase dialysate ow rate to
improve the delivered Kt? BMC Nephrology 2015; 16:20.
doi:10.1186/s12882-015-0013-9.
10. Bhimani JP, Ouseph R, Ward RA. Effect of increasing
dialysate ow rate on diusive mass transfer of urea, phosphate
and B2-microglobulin during clinical hemodialysis. Nephrol
Dial Transplantation 2010;25(12):3990-5.
11. Daugirdas JT, Schneditz D. Overestimation of hemodialysis
dose depends on dialysis eciency by regional blood ow but
not by conventional two pool urea kinetic analysis. ASAIO J
1995; 41: M719-M724.
12. Aslam S, Saggi SJ, Salifu M, Kossmann RJ. Online measurement
of hemodialysis adequacy using eective ionic dialysance of
sodium-a review of its principles, applications, benets, and
risks. Hemodialysis Int 2018; 22:425-34.
13. Molano-Trivino A, Meid B, Guzman G, et al. Eect of decreasing
dialysis uid ow rate on dialysis ecacy and interdialytic
weight gain in chronic hemodialysis-FLUGAIN Study. Nephrol
Dial Transplant 2018;33 (Suppl 1): i514-i515.
14. Ahrenholz P, Taborsky P, Bohling M, Rawer P, Ibrahim N,
Gajdos M, et al. Determination of dialysis dose: A clinical
comparison of methods. Blood Purif 2011;32: 271-7.
15. Cheung AK, Agodoa LY, Daugirdas JT, Depner TA, Gotch
FA, Greene T, et al. Eect of hemodialyzer reuse on clearances
of urea and β2-microglobumin. J Am Soc Nephrol 1999;10:
117-27.
16. Ouseph R, Smith BP, Ward RA. Maintaining blood compartment
volumes in dialyzers reprocessed with paracetic acid maintains
Kt/V but not B2-microglobulin removal. Am J Kidney Dis
1997;30: 501-6.
17. Tarrass F, Benjelloun M, Benjelloun O, Bensaha T. Water
conservation: an emerging but vital issue in hemodialysis
therapy. Blood Purif 2010;30: 181-5.
18. Yau A, Agar JWM, Barraclough KA. Addressing the Environmental
Impact of Kidney Care. Am J Kidney Dis 2021;77: 406-409.
19. Denny GB, Golper TA. Does hemodialyzer reuse have a place
in current ESRD care: “to be or not to be?” Semin Dial 2014;27:
256-8.
20. Upadhyay A, Jaber BL. Reuse and Biocompatibility of Hemodialysis
Membranes: Clinically Relevant? Semin Dial 2017;30: 121-4.
Srisuwan et al.
