JOURNAL OF DIALYSIS, 2 ( 4 ) , 347-359

(1978)

EVALUATION OF THREE DRY-STERILIZED HOLLOW FIBER ARTIFICIAL KIDNEYS

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A. Streifel J. Ebben C. Sahr R. Meyer J. Shideman R. Lynch C. Kjellstrand Departments of Medicine and Surgery University of Minnesota 420 Delaware Street, S.E. Minneapolis, Minnesota 55455 ABSTRACT We investigated three new dry sterilized hollow fiber artificial kidneys (HFAK) (Cordis Dow CDAK 1.3, Travenol CF 1200, Extracorporeal Tri-Ex 1). Dry sterilization makes these diaJyzers more economical by shortening set-up time. Dry sterilization also eliminates iatrogenic administration of residual sterilant. Water of imbibition can significantly increase the blood compartment volume of the dialyzer during dialysis. Consequently, a corrected blood volume for each dialyzer was established; these corrected volumes varied from 13-36% greater than the volume determined before dialysate flow. With low dose heparinization of these dialyzers there was between an 18 and 45% decrease in the post dialysis volume, presumably due to fiber clotting during dialysis. This volume added to the residual blood loss measured by a colorimetric technique accounted for a possible blood loss ranging between 26.9 and 53.9 ml per dialysis for these three dialyzers. Our results suggest that a relationship between dialyzer clotting and decreased dialyzer efficiency may exist. These three capillary flow dialyzers had a much lower platelet drop (0-9%pre to post) when compared to 30-40% drop of flat plate dialyzers. These dialyzers were found to be safe and easy to use but the high fiber clotting warrants further investigation in chronic dialysis patients on high dose heparin.

INTRODUCTION We recently evaluated three new dry sterilized hollow fiber artificial kidneys (HFAK) (Travenol CF 1200, Extracorporeal Tri-Ex 1 , 347 Copyright 0 1 9 7 8 by Marcel Dekker, lnc. All R ~ g h uReserved. Neither this work nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage and retrieval System. without permission in writing fromthe publisher.

STREIFEL ET AL.

34 8

and Cordis Dow CDAK 1.3). many advantages.

Dry sterilization of hemodialyzers has

It shortens the set-up time considerably since

it is not necessary to wash out the formaldehyde with 0.9% saline.

In addition, formaldehyde, because of its smell and skin irritation is unpleasant to work with.

Finally, episodes of local pain and

hemolysis have been reported during the use of formaldehyde as a sterilant for hemodialyzers (1,Z).

These dialyzers were evaluated

by the usual i n vivo and in vitro parameters (3,4).

We were parti-

cularly interested in fiber clotting secondary to our low dose

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infusion of heparin (5) since our patient population consists of many pre and post surgical patients. Another goal of this evaluation was to evaluate thrmbocytopenia occurring during dialysis since this has been reported to occur during hemodialysis (6).

MATERIAL AND METHODS We evaluated 45 dialyzers (Tri-Ex 1, 18: CF 1200, 16: CDAK 1.3, 1 1 ) over a period of three months in seventeen different patients. The clinical evaluation of these new dialyzers followed previously recomnend techniques (3,4).

The parameters studied are outlined in

Table I. Each dialyzer was evaluated in a vertical position, with the arterial end of the dialyzer uppermost, using a single-pass dialysate flow of 500 ml/min.

Comnercial dialysate with a glucose concentration

o f 250 mg% was used.

Anticoagulation during dialysis was accomplished

by a previously described heparin infusion technique (5), with LeeWhite clotting times maintained between 10 and 50 minutes.

All

dialyzers were primed with 1 liter of 0.9% normal saline to which 2,000 units of sodium heparin had.been added.

HOLLOW FIBER ARTIFICIAL KIDNEYS

349

TABLE I PARAMETERS STUDIED 1.

Ease of operation, set-up

2. Prime volume (Q, 500-corrected 6 hr. vol.) 3. Compliance (m1/100 m H g ) 4. % leak rate

5. Pressure drop across dialyzer ( m H g at QB 350,QD 500)

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6. Ultrafiltration rate (UFR) gm/hr/100 mnHg 7.

BUN Clearance (ml/min Q, at 200 ml/min) (BUN)

a.

%

dialyzer efficiency drop (BUN clearance at 1 vs. 6 hrs.)

9. Residual blood volume (RBV) ml/dialyzer

10. % volume o f dialyzer clotted 11.

Heparin usage per 6 hour dialysis run

12. Platelet drop (pre vs. post

= %

drop)

13. Clotting times (modified Lee-White)

Priming volume was measured in vitro by filling the dialyzer with corn oil before initiating the dialysate flow. Then dialysate flow was initiated at 5UO ml/min with a transmembrane pressure less than 30 m H g .

The compliance of the blood compartment was measured

in vitro by distending the blood compartment with corn oil against an occluded venous outflow line. Variation in the relationship between volume and total transmembrane pressure was recorded up to 500 m H g . During these experiments dialysate flow was maintained for six hours at 500 ml/min and a temperature of 37OC.

Blood and

dialysate pressure drops across the dialyzer at varying blood flows were determined by monitoring blood and dialysate pressures imne-

STREIFEL ET AL.

350

diately before and after the inflow and outflow of either dialysate or blood at a constant dialysate flow of 500 ml/min. Ultrafiltration was determined in vivo by measuring weight loss on a constant monitoring Potter Model 26B bed scale over either onehalf or one-hour periods at a constant transmembrane pressure. Transmembrane pressure was determined by taking the mean venous outflow pressure and adding it to the mean negative dialysate pressure. Patient weight

106s

was corrected for fluid and solid

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intake and output during periods of ultrafiltration measurement. The blood pumps were calibrated just prior to being used for clearance determinations. Blood urea nitrogen (BUN) clearances were done in vivo from arterial and venous blood samples drawn up t o one and six hours of dialysis. These blood samples were utilized to determine whether or not there was a decrease in clearance at the end of the dialysis procedure. BUN concentrations were measured on a Beckman BUN analyzer. The formula: Clearance = blood flow (ml/min) X (arterial concentration-venous concentration) arterial concentration was used for the calculation of small molecule BUN klearances. Ultrafiltration was ignored in the calculation of clearance. The convective component for BUN is small compared with total clearance. Residual blood loss in the dialyzer was measured after a 500 ml normal saline wash to the patient. Blood lines were then disconnected and the amount of residual blood in the dialyzer was determined by a colorimetricmethod. The post dialysis volume was determined by applying air pressure to the dialyzer thus extracting remaining fluid into a flask for measurement. This volume was then compared to our corrected in vitro prime volume for the % of dialyzer clotted. The

351

HOLLOW FIBER ARTIFICIAL KIDNEYS

corrected dialyzer volume is the volume obtained after allowing dialysate flow of 500 ml/min for 6 hours. This was measured since it has been shown that prolonged wetting causes fibers to swell through water imbibition. If this correction was not done and one compared post dialysis volumes to uncorrected pre dialysis volumes, one would tend to underestimate the amount o f clotting in the dialyzer. Heparin usage was recorded during the six hours of dialysis. We utilize a constant heparin infusion technique in which 5,000

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units areadded to 150 ml solution of normal saline (approximately 33 units/cc) and infused at varying rates ( 7 ) .

Platelet drop was

determined by drawing a blood sample just prior to dialysis and during dialysis from the patient during the last 15 minutes of dialysis. Platelet counts were determined on a model ZBI Coulter Counter.

RESULTS These dialyzers proved to be convenient and easy to use.

The

time and cost of set-up was decreased considerably, compared to formaldehyde sterilized dialyzers where large amounts of a flush solution are normally required. Table I1 presents the technical information, as well as the results of the in vitro testing of the three hollow fiber artificial kidneys. The corrected volumes o f the dialyzers after 6 hours of dialysate f l o w ranged from 13% t o 36% greater than the volume obtained before initiating dialysate flow. The compliance of the fibers for all dialyzers was less than 1 m1/100 mnHg transmembrane pressure. None of the dialyzers leaked or ruptured during the clinical evaluation.

STREIFEL ET AL.

352

TABLE I 1 FROM I N VITRO TESTING

TECHNICAL INFORMATION AND DIALYZER DATA Membrane Type 6 Thickness (u)

Surface Area (n21

*an

ValD 2 0

COAK 1.3’

CF 1200’

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Tri-Ex l 1

Regenerated Cellulose 30 u

1.3

Cuprophan 16 u

1.3

Cuprophan 11 u

1.a

n=3

Prime Volume Blood Canpartment ( m i ) Vo105003

Val6 hr.4

X Increase

- - + 36 n.3

84

108

fl-3

n J

106

118

n=4

n.4

88

98

11s t13

120 + 19 105

Ethylene oxide sterilized Before initiation of dialysate flcu

0, 05ao

-

Ten minutes after initiation o f dialysate flow of SO0 cc/min

Val6.,,,= Volume a f t e r 6 hours (corrected volume)

n

Number of determinations

OX leak rate on a l l dialyrers

The in v i v o results for BUN clearance are illustrated i n Figure 1 for blood flows ranging from between 100 and 300 ml/min.

Table 111

compares BUN clearances at blood flows of 200 and 300 ml/min and a dialysate flow of 500 ml/min, as well as the results of the decrease in dialyzer efficiency with time. After 6 hours of dialysis, there was a 9% to 25% decrease in BUN clearance (Table 111). The mean pressure drops across the dialyzers for blood and dialysate (QB = 350 rnl/min, Q, = 500 ml/min) are shown in Table 111. Under normal operating conditions, there i s little resistance for either blood or dialysate flow.

HOLLOW FIBER ARTIFICIAL KIDNFLS

353

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Clearance B U N

In vivo BUN clearance versus blood flow for three dry sterilized hollow fiber artificial kidneys. Data obtained one hour after initiating dialysis; n=number of determinations.

Table 111 and Figure 2 illustrate the in vivo results for ultrafiltration rate ranging between the transmembrane pressures of 130 and 500 mnHg.

In vivo, ultrafiltration rates were linear between

130 and 500 mnHg based upon a linear regression analysis (Figure 2).

Based upon linear regression analysis, in vivo ultrafiltration rates were comparable for two dialyzers (CF 1200 and Tri-Ex 1), and considerably less for CDAK 1.3.

This difference is most likely due to

the fact that the CDAK 1.3 has a thicker membrane (30 u) compared to either the CF 1200 (16 u) or the Tri-Ex 1 (11 u). Lee-White clotting times were routinely done at regular intervals on all patients.

The mean Lee-White clotting time was calculated for

354

STREIFEL ET AL.

TABLE I11

IN VIVO RESULTS Pressure drop' across dialyzer (mw)

CDAK 1.3

CF 1200

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Tri-Ex 1

Clearance (nl/min)

U1 t r a f i 1t r a t i o n

rate gn/hr/100 d i g

Blood

Oialysate

N = 12

N- 12

164

4 3 . ~ 1 4 . 3 38.3218.9 N-14

N.14

50.0210.6

36.8+18.7

N.14

N-12

58.6z25.1

21.2+16.5

326

323

F I r~a t e =

Q, = 500

BUN

1 hr.'

1 hr.3

6 hr.3

N-8

N.4

N = 4

139.5t9.7

182.6212.2

136.230.5

N - 8

N.6

N = 6

153.9f11.6

190.5~15.2

173.4229.8

n-9

N - 4

n = 4

136.1T12.3

152.5r24.1

135.2?36.7

,4

25

9

11

ml/min

pg = 350 ml/min values a t

oB =

ZOO ml/min

QD

500 ml/min

-

values a t Q~ = 300 m l / m i n

Qo = 500 nl/min I decrease in efficiency 1

-

6 hrs.

C l e a r a n c e s a t l and 6 hrs. a f t e r i n i t i a t i o n o f d i a l y s i s Values

standard deviation

N = number of determinations

each dialyzer evaluated (Table IV), since this factor was considered to be important when comparing fiber clotting. The percent volume of the dialyzer clotted was smallest for the CF 1200, however, the patients on the CF 1200 also had the longest clotting time (Table IV).

usage was greatest for the CF 1200 and the Tri Ex 1.

Heparin

Platelet drops

across the dialyzers varied between +2% to -9%. Residual blood volume was measured in 17 of the hollow fiber artificial kidneys after

HOLLOW FIBER ARTIFICIAL K I D N E Y S

355

Ultrafiltration Rates Obtained During Clinical Dialysis Treatment 1800

1600 h

L

c

E

Q

Y

J

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r

1400

-

-

-

1000 1200

800

-

UFR 1.6 r'=-4

600-

Transmembrane Pressure ( mm Hg) FIG. 2

Average u l t r a f i l t r a t i o n rates f o r three dry s t e r i l i z e d hollow f i b e r a r t i f i c i a l kidneys obtained d u r i n g clinical d i a l y s i s (transmembrane pressure = mean negative dialysate pressure + mean venous outflow pressure; u l t r a f i l t r a t i o n r a t e = UFR; r2 = coefficient of determination).

six hours of dialysis and varied between 4.4 and 6.9 ml/dialyzer f o r the three dialyzers evaluated (Table IV).

Dialyzer blood compartment

volume was determined a f t e r 6 hours o f d i a l y s i s for the three hollow f i b e r dialyzers.

These p o s t d i a l y s i s volumes were then compared t o

the mean pre-dialysis blood compartment volumes. presented in Table IV.

These r e s u l t s a r e

After 6 hours of dialysis blood compartment

volume decreased by 26% i n 4 COAK 1.3 dialyzers and 45% i n 5 Tri-Ex 1 dialyzers.

Thus, there was between an 18 and 45% decrease post dialysis

volume, presumably due t o f i b e r c l o t t i n g or occlusion d u r i n g d i a l y s i s .

356

STRELFEL ET AL.

TABLE I V

IN VIVO RESULTS blood loss I'm1 blood/ dialyzcr)

Mean vollime* hpartn Platelets 1 0 0 0 / ~ ~ of dialyzer usage clotted (USP u n i t s ) Pre Post I as X and (ml)

N = 5

N - 4

Rcs1dual

COAK 1.3

4.4

? 1.7

N

4526t1527

26

(3096)

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CF 1200

Tri-Ex 1

N - 6

N . 6 ,

5.9 ? 5.2

18 (21C12)

N - 6

N - 5

6.9 C 6.6

45 ( 4 7 9 1)

332 C156

303 +136 N

3967Z1610

206 f78

254 2114

f

204 f75 N

403221130

-

-

258 z137

10 -8.7

15 -1

15 +2

Mean c l o t t i n g times ? SO (range) N

-

16

2 2 8 (10-38)

N = 36

3 2 9 (12-50)

N

-

43

25?7 (12-50)

Posbdialysis extracted volume canpared t o corrected volume

-

+ Modified Lee-Wh

Evaluation of three dry-sterilized hollow fiber artifical kidneys.

JOURNAL OF DIALYSIS, 2 ( 4 ) , 347-359 (1978) EVALUATION OF THREE DRY-STERILIZED HOLLOW FIBER ARTIFICIAL KIDNEYS Ren Fail Downloaded from informahe...
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