Effects of high-dose aprotinin on renal function in aortocoronary bypass grafting

Effects of High-Dose Aprotinin on Renal Function in Aortocoronary Bypass Grafting Peter R. Feindt, MD, Sandra Walcher, MD, Ingo Volkmer, MD, Hans E. Keller, MD, Uwe Straub, MD, Hanno Huwer, MD, Ulrich T. Seyfert, MD, Thomas Petzold, MD, and Emmeran Gams, MD Departments of Thoracic and Cardimascular Surgery and Clinical Chenlistrv, Homburg University Hospital, Homburg/Saar, Germany

Background. To reduce blood c o n s u m p t i o n in cardiac surgery, aprotinin has been widely used for years. Because aprotinin is metabolized in the kidney, damage of the renal system has been discussed. Methods. To study these possibly unfavorable effects of aprotinin, a prospective, randomized, placebo-controlled study of 20 patients u n d e r g o i n g aortocoronary bypass operations was performed. A placebo group P was compared with group A, in which patients received high-dose aprotinin according to the "Hammersmith'" regimen. Renal function was assessed for 5 postoperative days using sodium dodecyl sulfate gel electrophoresis and quantitative protein analysis of the urine. Results. During and after the operation, temporary renal dysfunction was found in all patients, with a substantial increase of all investigated iTldices. The ¢r~microglobulin level in the urine was significantly increased in the aprotinin group for 5 days in comparison with the placebo group, with a m a x i m u m on the third postoperative day (64.8 - 13.7 versus 21.0 + 6.5 rag/L; p <

0.05). Similarly, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the bands of proteins filtrated in the renal tubular system were almost tripled in the aprotinin group 5 days postoperatively (5.0 ± 0.8 versus 2.1 - 0.2; p < 0.05). Although urine production was significantly increased in group A (4789 ± 580 versus 3653 ± 492 mL/24 h postoperatively; p < 0.05), no relevant changes in serum or urine creatinine levels could be observed in either group. Conclusions. Patients undergoing aortocoronary bypass operations demonstrate a temporary renal dysfunction. Aprotinin impairs renal function in addition by overloading the tubular reabsorption mechanisms. Patients with normal renal function preoperatively--as were included in this study--are able to compensate for both the perioperative renal dysfunction caused by the extracorporeal circulation and the additional tubular damage due to aprotinin.

lthough c a r d i o p u l m o n a r y bypass is a standard method in cardiac surger v, it can cause various complications, including damage to the corpuscular comp o n e n t s of blood. These disorders become evident as hemorrhages in 3% to 5% of cases [1, 2l. The intraoperative administration of the proteinase inhibitor aprotinin leads to a known reduction of intraoperative and postoperative blood loss and thus to less consumption of foreign blood in patients w,ho are operated on by means of cardiopulmonary bypass [3-51. The characteristics of the enzyme inhibitor aprotinin are based on the inhibition of trypsin, plasmin, and tissue and plasma kallikrein [6]. Aprotinin has a high affinity for the renal tissue and is rapidly eliminated from the circulation bv glomerular filtration (t,s, 1 to 2 hours). After 4 hours, 80'!,, to 90'!, o{ the administered dose is stored in the proximal tubular cells before excretion as active protein 171. Because of this metabolism, there is a possibility that kidney function might be affected bv the use of the high doses of aproti-

nin currently recommended. To study these possibly unfavorable effects of aprotinin, we observed renal function for 5 days postoperatively using highly sensitive indices of the glomerular and tubular function of the kidney.

A

Accepted for publicationMa~ 16, Iq~5. Address reprint requests to Dr (,alll~ lh'partmunt ,~1 Ihoracic and Cardiovascular Surgery, Universitx Hospital, 6642l Ihmlburg/Saar,(;ermany. © 1995 bv The Society of 1 horatio Surguon-

(Ann Thorac 5urg 1995;60:1076-80)

Material and M e t h o d s Tile study protocol was approved by the institutional ethical committee, and informed consent was obtained. Twenty patients who u n d e r w e n t an aortocoronary bypass operation were investigated in a prospective, randomized, double-blind study. Exclusion criteria were reoperations, emergency interventions, preoperative administration of thrombocyte inhibitors or antirheumatic agents with a similar action, an ejection fraction of less than 40'!,,, known blood clotting disorders, use of a cell saver, and preoperative renal dysfunction. Two groups each comprising 10 patients were formed: group P served as the control group, and group A received high-dose aprotinin with 2,000,000 kallikrein inhibitor units at the induction of anesthesia, 2,000,000 KIU added to the priming volume of the heart-lung machine, and 500,000 KIU/h during the operation 141. Urine samples were 0003-4975/95159.50 SSDI 0003-4975(95)00525-P

Ann Thorac Surg 1995;60:1076 80

FEINDT ET AL INFLUENCE OF A P R O T I N I N O N RENAL F U N C T I O N

Table 1. Genenzl Patie~tt Data qf the Placebo ,rod the Aprotinin Groups" Characteristic

Placebo

Age (y) Ejection fraction Duration of operation (rain) Number of grafts Bypass time (rain)

66.4 ÷ 2.4 0.64 ~ 0.06 200 ÷ 6.8 2.7 L 0.4 67.1 * 6.2

Aprotinin 62.3 0.62 207 3.0 76.0

- 1.2 - 0.05 - 8.8 ÷ 0.2 * 5.6

"~All comparisons arc nonsignificant.

taken at the following times: (1) 1 day preoperatively, (2) immediately before the operation, (3) on the first day postoperatively, (4) the third day postoperatively, and (5) the fifth day postoperatively. The urine samples were taken from a urine catheter until the third postoperative day, after which samples were obtained from spontaneous urine. All samples were collected and stored at 20°C before they were processed further. The same surgical procedure was performed in all patients. The m e m b r a n e oxygenator Maxima-Hollow Fiber (Medtronic Blood Systems, lnc, Anaheim, CA) was used for the extracorporeal circulation. The perfusion volume was maintained at 2.4 L. min ~• m 2. The prime volume consisted of 2 L Ringer's lactate and 250 mL 5",, h u m a n albumin. During extracorporeal circulation, mild hypothermia of 28°C was applied. Heparin was given at 300 USP per kilogram body weight. Heparinization was controlled with the activated clotting time (HemoTec, Inc, Englewood, CO) to maintain the clotting time greater than 480 seconds.

Laborato~ Methods Only methods that are n o t routine in every clinical chemistrv laboratoD' are specified here. The sodium dodecvl sulfate-polyacrylamide gel electrophoresis was performed using the method of Shapiro 181 and Boesken a n d Mamier [9]. Gels of 0.48 mm with a linear pore gradient (4% to 22.5", T and C constant) were produced in a size of 120 ~ 250 mm and were polymerized on a plastic film. After a first electrophoresis for 15 minutes with 600 V, 30 W, and 20 mA, the main electrophoresis was started for 120 to 140 minutes with 600 V, 30 W, and 50 mA. After this, the gels were stained with the

mg/L

70

# ~14

I

# :

6O

modified silver method of Heukeshoven a n d Dernick [10]. The evaluation was carried out with a densitometer (Eliscript 400; ATH, Neuried, Germany), a n d molecular weights were d e t e r m i n e d using calibration curves [11]. A l p h a - l - m i c r o g l o b u l i n and a l b u m i n were d e t e r m i n e d by adding specific antibodies to the urine, a n d changes were m e a s u r e d quantitatively with tyndallometry (Behring Nephelometer Analyzer; Behring, Marburg, Germany). Total proteins were measured by n e p h e l o m e t r y after precipitation with trichloroacetic acid. Creatinine was determined using the BM/Hitachi System at a wavelength of 570 n m (Boehringer, M a n n h e i m , Germany).

Statistical Analysis Statistical analysis of the results was carried out with the SPSS-X 4.0 program (SAS Institute Inc., Cary, NC). Dep e n d e n t variables were further examined using the F r i e d m a n n test; i n d e p e n d e n t variables were examined by m e a n s of the Kruskal-Wallis test. Comparisons a m o n g the individual groups were done with the M a n n - W h i t n e y U test. All results were expressed as m e a n s -- standard deviation. The level of significance was p less than 0.05.

Results The general patient data are presented in Table 1. There were no significant differences between the groups in age, height, weight, ejection fraction, duration of operation, bypass time, or n u m b e r of aortocoronary grafts established. The same a m o u n t s of diuretic agents were used in both groups.

Changes Due to Open Heart Operation With Cardiopulmonary Bypass I n d e p e n d e n t of the use of aprotinin, there were significant intraoperative increases in ~ - m i c r o g l o b u l i n and in the bands of tubular and glomerular filtrated proteins when compared with the preoperative values (p < 0.01).

Changes Due to Aprotinin The ~'~-microglobulin level in the urine was significantly increased in the aprotinin group at 3 a n d 5 days postoperatively, with a m a x i m u m on the third postoperative day (64.8 ÷ 13.7 versus 21.0 + 6.5 mg/L; p < 0.05) (Fig 1). Similarly, in the sodium dodecyl sulfate gel electrophoresis, the bands of proteins filtrated in the renal t u b u l a r

p < 0.05

5O 40

D placebo group 1 • aprotinin groupJ /

3O 2O 10 0

pre-OP

intra-OP

1 day post-OP

3 days post-OP

time 5 days post-OP

1077

Fi~, 1. Chan~,es in ~h-microglobulin level in the urine (mean values ± standard deviation).

1078

FEINI)TEl AI INI-LLit!NCI{OF API),OTININ(,IN RtNA[ FLINCTION

Fig 2. Changes in the bands of tubuhtr filtr,ltcd t,roteins in t]lc urim' (/IICIIH-Otlhl('S + s t a t l d d r d lll'Uill tion).

Ann Thorac Surg 1995;60:1076-80

6 number 5 of bands

#

p < 0.05

4 2 placebo group • aprotinin group

3 2 1 0 post-OP

system were significantly elevated in the aprotinin group A 5 days postoperatively (5.0 - 0.8 versus 2.1 ~ 0.2; p < 0.05) (Fig 2). Although urine production was significantly increased in group A from the b e g i n n i n g of the operation until the first postoperative day (4,789 + 580 versus 3,653 _+ 492 mL; p < 0.01), no differences in serum or urine creatinine levels could be observed between the groups (Tables 2 and 3). There were also no differences in the b a n d s of the glomerular filtrated proteins (Fig 3), in the a l b u m i n level in the urine (Fig 4), or in total proteins in the urine (Fig 5) between the groups.

post-OP post-OP

time

In this prospective, randomized, double-blind study, ~se examined the influence of a high-dose aprotinin infusion on kidney function during aortocoronary bypass grafting. To investigate the effects of high-dose aprotinin on renal function, it was necessary to separate factors affecting kidney function other than aprotinin during the procedure. It is known that extracorporeal circulation itself impairs renal ftmction in patients having open heart operations ]12]. In agreement with these findings, our control group of patients showed significant intraoperative and postoperative increases in alpha-l-microglobulin and filtrated proteins in the urine conlpared with the

preoperative values (p < 0.01). This temporary, global i m p a i r m e n t of renal function is obviously caused by the mechanisms of extracorporeal circulation with moderate hypothermia, circulatory instability during operation, etc. The particular end point of this study, namely the effect of high-dose aprotinin on renal function during aortocoronary bypass grafting, was explored using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and quantitative protein analysis of the urine. The results of this clinical investigation correspond with results obtained in earlier studies on aprotinin, w h e n it was not yet widely used in cardiac surgery. Aprotinin is actively reabsorbed in the renal tubular system after glomerular filtration, and 80% to 90% of it is deposited in the ciliated border cells of the proximal tubuli within a few hours after intravenous administration. It accumulates there for 12 to 24 hours, is stored in the phagosomes, a n d - - u n d e r energy c o n s u m p t i o n - - i s metabolized and eliminated within 5 to 6 days [4, 7, 13]. In our study, we were able to reproduce this metabolism of aprotinin. A significant difference between the control and the aprotinin group was observed on the third and fifth postoperative days for alpha-l-microglobulin and the n u m b e r of protein bands filtrated in the renal tubular system, with a considerable increase in the aprotinin group. Both indices are selective and highly sensitive markers for tubular

Table 2. Serum Creatinim' l.evcl on.4/dL) Hw l)ay Before and the Day After the Operation in the Plm cbo (,rou)~ and the Aprotinin Group"

Tabh' ,3. Urine Creatmine Level (mg,/dL) the Day Before and the I)ay /~fter the Operation in the Placebo Group and the .'tFrotinin Group '~

Comment

Placebo Group Patient

Aprotinin Group

Preop

Post~ p

l'reop

Postop

Patient

1

1.0

1.4

{1.q

1.2

I

2 3 4

1.5 1.3 1.0

1.5 1.9 1.2

1.2 1.~ 1.2

1.3 2.2 1.5

5

1.3

1.4

0.8

1.2

6 7 8

1.2 I .o 0.8

1.4 1.5 1.1

1.4 1.2 1.9

9

1.1

1.5

10

1.6

2.2

I. I 0.7 1.2 I .il o.tl

2 3 4 5 6 7

'~ T h e r e w e r e no statistically significant dil~ercnces.

1.2

1.3

Aprotinin Group

Placebo Group

9 II~ ' [here

~cre

Preop

Postop

75 155 11 14 155 75 35 95 45 119

75 15 65 10 180 105 85 39 85 180

Preop

no statistically significant differences.

25 15 65 30 2O 50 10 10 135 100

Postop 45 75 45 124 50 10 60 90 20 100

Ann Thorac Surg 1995;60:1076-8()

FEINDT E~f AL INt:LUENCE OF APROTININ ON RENALFUNCTION

f ig 3. Changes in the bamls q t g l o m e n d a r filtrated proteins in the urine (mean values + standard deviation).

4

~0.5

number 3.5 of bands 3

•

2,5

~

2 1,5

0.5

0

*h -

i o-.i i

~o.3

pre-OP

intra-OP

post-OP

post-OP post-OP

group • aprotinin group

time

proteinuria. The sodium dodecvl sulfate gel electrophoresis facilitates an exact local differentiation of the malfunction between the glomerular and the tubular system on the basis of the protein pattern. The m e t a b o lism of aprotinin described above causes a reduction in kidney function with a reversible overload of the tubular reabsorption mechanisms. Our results correspond with those of Fraedrich and co-workers [12], who were able to d e m o n s t r a t e a significant increase in the tubular markers after use of aprotinin as a sign of tubular overloading. This t e m p o r a D, dysfunction of the kidney caused by aprotinin has been observed so far by only two working groups [12, 131. Thus, the assessment of renal function only on the basis of preoperative and postoperative levels of s e r u m creatinine is obviously insufficient. Our results, as well as those of other authors, confirm this fact [12, 14, 15], as we were unable to d e m o n s t r a t e significant differences between the groups in creatinine levels either in the blood or in the urine. Severe d a m a g e of the renal p a r e n c h y m a by aprotinin cannot be confirmed. The d o s e - d e p e n d e n t increase in serum creatinine reported by Cosgrove and associates [16] was not seen in our study. The increase of a l b u m i n that we observed in the urine can be explained by tubular dysfunction. This increase of albumin is followed by an increase of total protein as well, of which albumin constitutes the largest part. Despite the considerable increase of protein in the aprotinin group c o m p a r e d with the placebo group, no statistical significance could be found, possibly because of the high s t a n d a r d deviation and the small size of the groups (n 10). There was no difference in the n u m b e r

mg/L

of g l o m e r u l a r filtrated proteins between the placebo a n d the aprotinin group. This was unexpected, because of the free glomerular filtration of aprotinin in the kidney. We found a significant increase in the perioperative urine w)lume, which corresponds to the results of other groups J3, 12]. The reason for this r e m a i n s uncertain; a possible explanation is p r o v i d e d by the results of Blauhut a n d colleagues [14], who observed a rise in the osmolaric clearance and s o d i u m excretion during aprotinin therapy. On the basis of this s t u d y - - i n patients with n o r m a l renal function p r e o p e r a t i v e l y - - w e were unable to r e p r o duce the disquieting results of S u n d t and associates [171, who o b s e r v e d renal d a m a g e in 65% of their patients after the administration of aprotinin. This d a m a g e in turn necessitated dialysis in 25% of the patients a n d was followed by a high mortality rate. In addition to the fact that this earlier study [17] was a retrospective evaluation, a comparison with our study is not possible because the patients described earlier had aortic operations and extensive surgery, different m o d e s of h y p o t h e r m i a , different dosages of heparin, and higher blood losses, a m o n g other differences. Postoperative renal failure c o m m o n l y represents the end point of a multifactorial course of events, in which the age of the patient, p r e o p e r a t i v e renal function, perioperative medication, the duration of operation and depth of hypothermia, a n d the perfusion quality play an important role, in addition to the administration of aprotinin. Therefore, the simple use of m e a n values for individual indices does not help to d e t e r m i n e p r e o p e r a -

Fig 4. Changes in albumin level in the urine (mean values - standard deviation).

120 100

80 placebo group I n aprotinin group]

60

i

40 20 0

1079

pre-OP

intra-OP

1 day post-OP

3 days post-OP

5 days

post-OP

time

1080

FEINDTET AI. INFLUI:~NCEO1 ,,\I'I4OIlNIN

t'JN

Ann Thorac Surg 1995;60:1076-80

R} N \l ILiNCTION

Fig 5, Chan£,es in the level v? total prvtculs itl the urim' (mean values - shltldord lh'viatunzl.

180 mg/L 160 140 120 100

3 placebo group

80

• aprotinin group

60 40 20 0

tively those patients at risk. In o u r o p i n i o n , the d o s a g e of a p r o t i n i n for patients with r e d u c e d renal function p r e o p e r a t i v e l y s h o u l d be a d a p t e d accordingly, as p r o p o s e d by several studies [12, 18]. As long as there are no larger studies on this type of patient, the use of aprotinin s h o u l d be h a n d l e d like the application of a m i n o g l y c o s i d e s in p a t i e n t s with i m p a i r e d renal function. A m i n o g l y c o s i d e s are m e t a b o l i z e d in the k i d n e y like aprotinin. In clinical applications, the d o s a g e s h o u l d be r e d u c e d for patients with levels of s e r u m c r e a t i n i n e of 2 m g / d L or greater. In conclusion, in patients u n d e r g o i n g o p e r a t i o n s with e x t r a c o r p o r e a l circulation, tenrporary renal dysfunction can occur for 5 days p o s t o p e r a t i v e l y . A p r o t i n i n e n h a n c e s this d y s f u n c t i o n by o v e r l o a d i n g the t u b u l a r r e a b s o r p t i o n m e c h a n i s m s . Patients with n o r m a l p r e o p e r a t i v e renal function w e r e able to c o m p e n s a t e for both the dysfunction due to the o p e r a t i o n and the additional i m p a i r m e n t c a u s e d by a p r o t i n i n itself. T h e use of h i g h - d o s e aprotinin can be r e g a r d e d as safe in these patients. Because of their low specificity, p r e o p e r a t i v e c r e a t i n i n e v a l u e s (in b l o o d a n d urine) a l o n e are not suitable for p r e d i c t i n g patients at risk. Patients with p r e o p e r a t i v e renal d y s f u n c t i o n m u s t be f u r t h e r d i a g n o s e d as far as (~.-microglobulin values are c o n c e r n e d . In cases of p r e o p e r a t i v e l y d o c u m e n t e d t u b u l a r d a m a g e (~h-microglobulin level g r e a t e r than 10 rag/L), an a d d i t i o n a l injury of the t u b u l a r s y s t e m by a p r o t i n i n s h o u l d be e x p e c t e d d u r i n g e x t r a c o r p o r e a l circulation. For t h e s e patients, we caution against the use of h i g h - d o s e aprotinin. References 1. Bachmann F, McKenna R, Cole tiR, Najafi H. 1he hemostatic mechanism after npen-heart surgery. I: Studies on plasma coagulation factors and fibrinolvsis in 512 patients after extracorporeal circulation. J Thorac Cardiovasc Surg 1975;70: 76- 85. 2. Moriau M, Masure R, Hurlet A, et al. Haemostasis disorders in open heart surgery with extracorporeal circulation. Vox Sang 1977;32:41-51. 3. Bidstrup BP, Roystnn D, Sapsford RN, I avlor KM. Reduction in blood loss and blood use after cardiopulmonarv bypass with high dose aprotinin (Tras~lol). I Thorac Cardiovasc Su rg 1989;97:364-72. 4. Roystnn D. High-dose aprotinin therap\: a review of the first

pre-oP

intra-oP

1 day 3 days 5 days post-OP post-OP post-OP

time

five \,ears' experience. J Cardiothorac Vasc Anesth 1992;6: 76-100. 5. Dietrich W, Barankay A, Dilthev G, et al. Reduction of humologous blood requirement in cardiac surgery by intraoperative aprotinin application: clinical experience in 152 cardiac surgical patients. Thorac Cardiovasc Surg 1989;37: 92-8. 6. Emerson TE. Pharrnacok)gy of aprotinin and efficacy during cardiopulmonary bypass. Drug Rev 1989;7:127-40. 7. Rustom R, Grime JS, Maltby P, Stockdale HR, Critchley M, Bone JM. Observations on the early renal uptake and later tubular metabolism of radiolabelled aprotinin (Trasylol) in man: theoretical and practical considerations. Clin Sci 1993; 84:231-5. 8. Shapiro A. Molecular weight estimation of polypeptide chain bv electrophoresis in SDS-polyacrylamide gels. Biochem B[ophys Res Commun 1967;28:815-20. 9. Boesken W, Mamier A. Molekulargewichtsbezogene Urinproteinelektrnphorese in der Diagnostik von Nierenkrankheiten. Lab Med 1985;9:285-91. 10. lteukeshoven J, Dernick R. Mechanism of silver staining of proteins in polyacrylamide gels. In: Schafer-Nielsen C, ed. Electrophoresis. 1st ed. Weinheim: VCH Verlagsgesellschaft, 1988:249 -56. I I. G6rg A, Pnstel W, Weser J, Schiwara H, Boesken W. Horizontal SDS electrophoresis in ultrathin pore-gradient gels tot analysis of urinary proteins. Sci Tools 1985;32:5-9. 12. Fraedrich G, Neukamm K, Schneider T, et al. Safety and risk/benefit assessment of aprotinin in primary CABG. In: Friedel N, Hetzer R, Royston D, eds. Blood use in cardiac surgery. New York: Springer-Verlag, 1991:221-32. 13. Fischer JH, Knupfer P. Hochdosierte Aprotinin (Trasylol)l'herapie--unschadlich fhr die Niere? Langenbecks Arch Chir 1983;360:241-9. I4. Blauhut B, Gross C, Necek S, Doran JE, Sp~th P, Lundsgaard-Hansen P. Effects of high-dose aprotinin on blood loss, ptatelet function, fibrinolysis, complement, and renal tunction after cardiopulmonary bypass. J Thorac Cardiovasc Surg 1991;101:958 67. 15. I.emmer JH, Stanford W, Bonney SL, et al. Aprotinin for coronary bypass operations: efficacy, safety, and influence on early saphenous vein graft patency. J Thorac Cardiovasc Surg 1994;107:543-53. 1¢~. Cosgrove DM Ill, Heric B, Lytle BW, et al. Aprotinin therapy for reoperative myocardial revascularization: a placebo-controlled study. Ann fhorac Surg 1992;54:1031-8. 17. Sundt FM, Kouchoukos NT, Saffitz JE, Murphy SF, Wareing TH, Stahl DJ. Renal dysfunction and intravascular coagulation with aprotinin and hypothermic circulatory arrest. Ann Thurac Surg 1993;55:1418-24. 18. Westaby S. Aprotinin in perspective. Ann Thorac Surg 1'793;55:1033- 41.