Comparative Analysis of Renal Function afterTreatment of Infrarenal Abdominal AorticAneurysms with a Suprarenal FixationDevice as Opposed to Open Surgery

Jose Miguel Zaragoz�a Garcıa, Eduardo Ortiz Monzon, �Angel Plaza Martınez, Francisco Juli�an

Gomez Palones, Jose Ignacio Blanes Mompo, Johissy Lissethe Briones Estebanez, Carlos

Martınez Parreno, Bader Al-Raies Bolanos, Vicente Sala Almonacil, �Alvaro Torres Blanco,

Ignacio Crespo Moreno, and Inmaculada Martınez Perello, Valencia, Spain

We analyzed the repercussions on renal function between suprarenal endograft fixation andopen surgery in the treatment of infrarenal abdominal aortic aneurysms (IAAAs) and determinedthe influential factors. Between 1999 and 2005, 59 IAAAs were treated with elective OS and 56with SEF. The serum creatinine (Cr) level and its clearance were determined before the proce-dure, in the intensive care unit (ICU), on discharge, and after 1, 6, 12, and 24 months. A dete-rioration in renal function was considered to be a >30% increase in Cr or a Cr >2 mg/dL. Aunivariate statistical analysis and a logistical regression analysis were carried out to determinethe predictive factors for repercussions on renal function. There were no statistically significantdifferences in the rate of renal exacerbation between the groups either on discharge ( p ¼0.52) or after 1 month ( p ¼ 0.483), 6 months ( p ¼ 0.451), 12 months ( p ¼ 0.457), and 24 months( p ¼ 0.682). The only significant difference was that detected in the ICU ( p ¼ 0.033). Diabetesmellitus, time spent in the ICU, postoperative intubation time, intraoperative transfusion, andtransfusion in the ICU were factors that influenced the deterioration of renal function in the uni-variate analysis. The only significant factor in the multivariate analysis was the need for transfu-sion in the ICU. Exacerbation of renal function occurred in both groups independently oftreatment type. In the immediate postoperative period, hemodynamic deterioration is more fre-quent in the open surgery group. Renal exacerbation tended to disappear in both groups duringfollow-up.

INTRODUCTION

Since the first description of endovascular repair of

an infrarenal abdominal aortic aneurysm (IAAA)

in 1991 by Parodi et al.,1 the use of this technique

as a treatment option has spread in such a way

that it is currently more common than open surgery

(OS). Nevertheless, despite the enthusiasm it has

Vascular Surgery Department, Dr. Peset Hospital, Valencia, Spain.

Correspondence to: Jose Miguel Zaragoz�a Garcıa, MD, C/ Isabel deVillena 2,18. 46160 Llıria, Valencia, Spain, E-mail: jozagar@hotmail.com

Ann Vasc Surg 2008; 22: 513-519DOI: 10.1016/j.avsg.2008.02.013� Annals of Vascular Surgery Inc.Published online: May 27, 2008

generated, approximately one-third of patients con-

tinue to be considered unsuitable for endograft. The

limitations for endovascular treatment are deter-

mined by IAAA anatomy, including inadequate

proximal fixation of the graft and the small size of

the iliac.2 Although there have been important ad-

vances in release devices, as well as in the endograft

itself, the excessive angle on the proximal neck and

its length are still limiting factors.

Despite the fact that recent clinical trials have

suggested that the risks associated with endovascu-

lar repair of IAAA are less than those for OS, there

is still great concern regarding durability.3,4 The in-

cidence of endograft migration and/or endoleak is

>30% in some cases,5,6 and these are often respon-

sible for the continued risk of aneurysm rupture that

513

514 Garcıa et al. Annals of Vascular Surgery

occurs in >1% annually.5,7 Suprarenal fixation

with uncovered stent has been proposed as a method

that could improve proximal fixation, allowing the

repair of necks with complex morphology or that

are short, thereby reducing the risk of later compli-

cations (migration, endoleak formation, and rup-

ture of the aneurysm).

Fixing the endograft to the suprarenal aorta re-

quires the insertion of a transrenal stent. It has

been implied that the effect of the stent clamps pass-

ing through the ostium of the renal arteries is a factor

in potential renal function deterioration. At the

same time, patients who undergo this type of treat-

ment are already at high risk of developing renal

complications given that they are of advanced age

and therefore have associated increased risk factors

and comorbidity. Also, many of them are diabetics

or have a history of previous renal insufficiency

(RI), which carries a greater risk. Therefore, deterio-

ration in renal function after endovascular repair of

IAAA can reach>20%, and the causes are normally

multifactoral, including mechanical causes, the ad-

ministration of nephrotoxic contrast agents, and

renal atheroembolism.8

With regard to OS, RI is the third most common

complication after treatment,9 and its presence is

a strong predictor of poor life expectancy.10 The

only independent predictive factor that has been

related to RI after surgical treatment of an IAAA is

previous RI.11 Despite precaution in preoperative

administration of intravenous contrast, intraopera-

tive administration of diuretic agents, and special

care with the placement and timing of the aortic

clamp, the incidence of postoperative RI is still sig-

nificant at about 6%, with a mortality rate of

28%.9,12 The deterioration in renal function in OS

of the IAAA has been attributed to atheroembolism,

renal ischemia, intraoperative hypertension in the

context of a hemodynamic deterioration, and tech-

nical factors related to renal arteries.13,14

We analyzed the repercussions of suprarenal en-

dograft fixation (SEF) on renal function compared

with OS in the treatment of IAAA and determined

the influential factors.

METHODS

Between 1999 and 2005, 160 IAAAs were treated in

our center, of which 59 were treated with elective

OS and 101 endovascularly, 59 of the latter

(58.4%) with Zenith� (Cook, Bloomington, IN)

SEF. Demographic data of the patients were col-

lected retrospectively in both groups and are shown

in Table I. One hundred percent of the patients were

male. In the SEF group, three patients had terminal

RI with periodic hemodialysis and were therefore

excluded from the study.

The suprarenal component of the Zenith endog-

raft is made up of 0.018-inch stainless steel wires;

the uncovered part is 26 mm long and is made up

of 10 or 12 supports (10 supports for diameters

<28 mm 12 supports for diameters �28 mm).

Each support ends distally in a 5 cm- or 0.093

inch-long hook. The suprarenal component is fixed

to the polyester graft with a monofilament stitch.

Treatment techniques for IAAA through SEF or

OS have already been described in other stud-

ies.15,16 The study of renal function in both groups

included establishing the concentration of serum

creatinine (Cr) prior to treatment, in the intensive

care unit (ICU), on discharge, and after 1-, 6-, 12-,

and 24-month follow-up. A study of the permeabil-

ity of the renal arteries as well as the detection of re-

nal hemorrhage was carried out through computed

tomography (CT) on discharge and after 1, 6, 12,

and 24 months.

To adjust the Cr figures to the age and weight of

the patients, Cr clearing (CrC) was calculated using

the Cockgraft-Gault formula: (140 � age) x weight/

Cr x 72.17-20 Exacerbation of renal function was de-

fined in our study as an increase>30% of Cr prior to

treatment or a value of Cr>2 mg/dL. Permeability of

the renal arteries was defined as continuity of con-

trast flow in the CT between the aorta and the

main renal artery. Data were also collected on sec-

ondary treatment carried out during the follow-up

related to renal problems as well as the need for

hemodialysis in any of the patients.

Regarding statistical analysis, dispersion mea-

surements were expressed as the mean ± standard

deviation, and those variables with extreme values

that could compromise the mean (amount of bleed-

ing and postoperative intubation time) were ex-

pressed as the median. Contingency tables with

the c2 test and the difference of proportions test

compared category and nominal variables of two in-

dependent samples, respectively; and the Mann-

Whitney U-test was used to analyze nonparametric

variables. Analysis of variance was applied to com-

pare the means or medians. For factors predictive

of the effects on renal function, a univariate analysis

was conducted using the c2 test and the Fisher test

for category variables and the Mann-Whitney U-

test for continuous variables. Later, a multivariate

analysis was carried out using logistic regression, af-

ter cataloguing the variables that were significant in

the univariate study, in order to determine those

variables with more specific weight as risk factors

for renal function deterioration. All results were

Vol. 22, No. 4, 2008 Analysis of renal function after treatment of AAA 515

Table I. Demographic data for SEF and OS groups

SEF group (n ¼ 56) OS group (n ¼ 59) p

Age (years) 72 (range 51-83) 66 (range 56-81) 0.385

Smoking 21.4% (n ¼ 12) 34% (n ¼ 20) 0.279

Diabetes mellitus 7.1% (n ¼ 4) 11.8% (n ¼ 7) 0.349

Arterial hypertension 73.2% (n ¼ 41) 72.8% (n ¼ 43) 0.600

Dyslipidemia 32.1% (n ¼ 18) 25.4% (n ¼ 15) 0.269

Hyperuricemia 10.7% (n ¼ 6) 8.4% (n ¼ 5) 0.519

Ischemic heart disease 35.7% (n ¼ 20) 28.8% (n ¼ 17) 0.468

Coronary surgery/stent 8.9% (n ¼ 5) 10.2% (n ¼ 6) 0.537

Other heart diseases 21.4% (n ¼ 12) 8.4% (n ¼ 5) 0.044

Previous CVA 12.5% (n ¼ 7) 6.7% (n ¼ 4) 0.235

COPD 26.7% (n ¼ 15) 18.6% (n ¼ 11) 0.206

GDU 10.7% (n ¼ 6) 13.5% (n ¼ 8) 0.429

Previous RI 12.5% (n ¼ 7) 6.7% (n ¼ 4) 0.235

Single kidney 7.1% (n ¼ 4) 5.1% (n ¼ 3) 0.471

ASA IV 76.7% (n ¼ 43) 37.2% (n ¼ 22) 0.001

CVA, cerebrovascular accident; COPD, chronic obstructive pulmonary disease; GDU, gastroduodenal ulcer.

analyzed using SPSS statistical software (SPSS, Inc.,

Chicago, IL).

RESULTS

The two groups were compared in advance; there

were no significant statistical differences in age,

risk factors, or prevalence of comorbidities except

for the prevalence of other, nonischemic heart dis-

eases ( p ¼ 0.044) and the anesthetic risk value

(greater prevalence of American Society of Anes-

thesiologists [ASA] IV in the SEF group with p ¼0.001) (Table I). The mean follow-up was 20 ±

15.7 months for the SEF group and 36.2 ± 17.7

months for the OS group. There were 13 follow-

up losses (11.3%), all of which were from the SEF

group and 10 of which were patients from other

health-care areas who preferred to carry out

follow-up tests in their own hospitals, as well as

those we were not able to contact by telephone;

the other three patients refused the CT tests and

analysis. Mean time in surgery was 190 ± 51 min

in the SEF group and 204 ± 59 min in the OS group,

and there were no significant statistical differences

between the groups ( p¼ 0.193). The mean contrast

dose used in the SEF group was 222 ± 82 mL. There

was no association between the amount of contrast

used and the degree of renal function exacerbation

in the SEF group. The mean aortic clamp time was

61.3 ± 21.2 min in the OS group. The suprarenal

clamp was only necessary in two cases (3.3%). Su-

prarenal aortic clamping did not influence the de-

gree of renal function exacerbation. The median

volume of bleeding was 250 mL for the SEF group

and 1,000 mL for the OS group, which is a statisti-

cally significant difference ( p ¼ 0.01). Intraopera-

tive blood transfusion was necessary in 28.5% of

cases in the SEF group (n ¼ 16), while in the OS

group it was needed in 81.3% of cases (n ¼ 48) ( p

< 0.001). The mean packed red blood cells trans-

fused in surgery in the SEF group was 0.7 and

that in the OS group, 2.8 ( p < 0.001). The median

postoperative intubation time was 0 hr in the SEF

group (most of the patients who underwent general

anesthetic were extubated in the operating theater),

while in the OS group it was 5 hr ( p ¼ 0.097). The

mean stay in the ICU was 1.2 ± 0.7 days in the SEF

group and 3.4 ± 2.8 days in the OS group ( p ¼0.018). A blood transfusion in the ICU was neces-

sary in 23.2% of cases in the SEF group (n ¼ 13),

while in the OS group it was necessary in 23.7%

of cases (n ¼ 14) ( p ¼ 0.562). The mean packed

red blood cells transfused in surgery in the SEF

group was 0.7 and that in the OS group, 0.8 ( p ¼0.665). The mean stay in hospital was 6.9 ± 3.2

days in the SEF group and 10.5 ± 8 days in the OS

group ( p ¼ 0.024). Postoperative morbidity was

1.7% in the SEF group (n ¼ 1) and 1.6% in the

OS group (n ¼ 1) ( p ¼ 0.634).

Table II shows the mean values for Cr and CrC.

Comparing Cr and CrC in the ICU and after 1, 6,

12, and 24 months with respect to the preoperative

Cr and CrC in each group, there were no significant

statistical differences, except in the Cr and CrC fig-

ures in the ICU of the OS group ( p < 0.05). Despite

the fact that there were no differences in the SEF

group, we observed an increasing tendency in Cr

and a decreasing tendency in CrC in the follow-

up, as shown in Figure 1.

516 Garcıa et al. Annals of Vascular Surgery

Table II. Cr and CrC values in follow-up

SEF group OS group p between groups

Cr p CrC p CrC p CrC p pCr* pCrC*

Preop 1.32 ± 0.46 62.8 ± 21.5 1.10 ± 0.37 77.3 ± 24.8 0.008 0.002

ICU 1.27 ± 0.43 >0.05 64.6 ± 21.1 >0.05 1.26 ± 0.60 <0.05 72.7 ± 27.4 <0.05 0.928 0.092

Discharge 1.32 ± 0.45 >0.05 62.3 ± 20.6 >0.05 1.14 ± 0.42 >0.05 75.2 ± 24.4 >0.05 0.044 0.004

1 month 1.30 ± 0.45 >0.05 62.5 ± 19.6 >0.05 1.14 ± 0.41 >0.05 74.6 ± 22.5 >0.05 0.065 0.004

6 months 1.32 ± 0.46 >0.05 62 ± 19 >0.05 1.13 ± 0.38 >0.05 74.4 ± 21.8 >0.05 0.030 0.003

12 months 1.35 ± 0.56 >0.05 60.9 ± 20 >0.05 1.15 ± 0.40 >0.05 73.6 ± 21.9 >0.05 0.032 0.003

24 months 1.37 ± 0.53 >0.05 60.8 ± 19.8 >0.05 1.18 ± 0.45 >0.05 73.7 ± 23.5 >0.05 0.096 0.013

p, comparison with preoperative values; pCr*, comparison of Cr between groups; pCrC*, comparison of CrC between groups.

Analyzing the deterioration of renal function (in-

crease >30% in Cr or Cr >2 mg/dL) which hap-

pened in the ICU in two patients in the SEF group

(3.6%) and in nine patients of the OS group

(15.3%), there was a significant statistical difference

between the groups ( p¼ 0.033). There were no sta-

tistically significant differences in the rate of renal

exacerbation between the groups either on dis-

charge (SEF 5.4% [n ¼ 3], OS 6.9% [n ¼ 4]; p ¼0.52) or after 1 month (SEF 5.4% [n ¼ 3], OS

3.4% [n ¼ 2]; p ¼ 0.483), 6 months (SEF 3.9% [n

¼ 2], OS 1.7% [n ¼ 1]; p ¼ 0.451), 12 months

(SEF 3.9% [n ¼ 2], OS 1.8% [n ¼ 1]; p ¼ 0.457),

and 24 months (SEF 2.7% [n ¼ 1], OS 2.1% [n ¼1]; p¼ 0.682) (Table III). In those patients with renal

function exacerbation, hemodialysis was not re-

quired. No cases of renal artery stenosis or occlusion

were found in the follow-up, nor were there any

signs of renal hemorrhage in the CT or the need

for a second intervention in relation to renal

problems.

Preoperative RI has been related to a greater risk

of deterioration in renal function following treat-

ment.11 To investigate this association in our sam-

ple, we analyzed the subgroup of patients with

previous RI (Cr >2 mg/dL). No patients in the SEF

group developed renal function exacerbation, while

in the OS group this deterioration occurred in one

patient (25%). This difference was not statistically

significant ( p ¼ 0.364).

To study those factors predictive of renal function

exacerbation in the ICU in the OS group, a univariate

analysis was carried out with the variable categories

prior RI, smoking, diabetes mellitus (DM), previous

ischemic heart disease, other heart diseases, single-

kidney patients, anesthetic risk, intraoperative asso-

ciated surgery, intraoperative autologous blood

transfusion, need for intraoperative transfusion,

and need for postoperative transfusion and with

the continuous variables age, length of operation,

volume of bleeding, postoperative intubation time,

packed red blood cells transfused in surgery and

the ICU, and length of stay in the ICU. The presence

of DM ( p ¼ 0.01), mean stay in the ICU ( p ¼ 0.01),

mean postoperative intubation time ( p ¼ 0.01),

need for intraoperative transfusion ( p ¼ 0.021),

and need for transfusion in the ICU ( p ¼ 0.011)

were factors that influenced the deterioration in re-

nal function in the univariate analysis. Later, a mul-

tivariate analysis was carried out through logistic

regression with those variables that were significant

in the univariate study, to determine which vari-

ables carried more weight in relation to the risk of de-

veloping renal function exacerbation; and a positive

association with need for transfusion in the ICU was

obtained (odds ratio [OR] ¼ 4.24, 95% confidence

interval [CI] 1.09-16.36).

DISCUSSION

Renal function exacerbation following IAAA treat-

ment, whether through open surgery or an endo-

vascular method, is a frequent complication;

some studies show it to be the third most common

complication in both treatment alternatives,9,21

and it is also a factor in poor survival prognoses.10

The cause of this deterioration is usually multifac-

torial; in OS the most common factors are renal

atheroembolism, renal ischemia after aortic clamp-

ing, hemodynamic deterioration, and iatrogenic

lesions in renal arteries (such as dissection or oc-

clusion). With endovascular treatment, radiological

contrast, which is potentially nephrotoxic, should

be included. Also, in the case of SEF, suprarenal

fixation increases renal morbidity,22 although

some studies have shown the safety of this type

of endograft.23-27

Despite there being no clear definition regarding

what constitutes an exacerbation of renal function,

most studies that have looked at this aspect measure

the Cr value as it is a parameter that is easy to obtain,

Vol. 22, No. 4, 2008 Analysis of renal function after treatment of AAA 517

increasing the sensitivity through definition of the

aforementioned deterioration as a 30% increase of

the base figure or an increase of >2 mg/dL.28-30

Also, CrC was calculated using the Cockgraft-Gault

formula, obtaining a parameter that better evaluates

renal function since it adjusts Cr to the weight and

age of each patient.

When analyzing the mean of the Cr and CrC fig-

ures in our preoperative series and comparing them

in the two groups, there were statistically significant

differences: The SEF group had significantly higher

figures, which can be attributed to the fact that

this group is of a more advanced age and has an as-

sociated comorbidity rate, and they had also under-

gone preoperative studies which used nephrotoxic

contrast (such as CT and arteriography) in a short

space of time. Nevertheless, if we compare the Cr

Treatment type

zenithsurgery

Mean

+

90

80

70

60

50

ACr pre-op.

ACr in ICU

ACr on discharge

ACr at 1month

ACr at 6 months

ACr at 12 months

ACr at 24 months

Treatment type

zenithsurgery

Mean

+

1.6

1.5

1.4

1.3

1.2

1.1

1.0

.9

Cr pre-op.(mg/dl)

Cr in ICU (mg/dl)

Cr on discharge (mg/dl)

Cr at 1m (mg/dl)

Cr at 6m (mg/dl)

Cr at 12m (mg/dl)

Cr at 24m(mg/dl)

Fig. 1. Graph of the evolution of Cr and CrC figures in

the SEF and OS groups.

and CrC figures for each group in the ICU, on dis-

charge, and after 1, 6, 12, and 24 months compared

to the preoperative values, we can see that there

were no statistically significant differences except

for the OS group in the ICU ( p < 0.05). Neverthe-

less, in the SEF group there was a progressive in-

crease in the mean values for Cr in the follow-up

and a decrease in CrC values, probably due to the

fact that these patients had follow-up treatment

using CT with contrast during the first 2 years

with a mean of five or six studies in 2 years, which

could contribute to this slight progressive deteri-

oration in renal function, a fact that other studies

corroborate (Fig. 1).30,31 Therefore, it has been

proposed that the frequency of these tests be re-

duced, especially during the first year, or that they

be substituted with noninvasive diagnostic tech-

niques such as the echo-Doppler test. Another

hypothesis that has been suggested to explain this

progressive increase in Cr figures is continued dam-

age to the renal arteries caused by the suprarenal

fixation stent.30 Nevertheless, the long-term effect

of arterial flow through the transrenal stent is

unknown, although it has been investigated on an

experimental level, which showed an increase in

turbulence in the area of the stent but no decrease

in flow.32

Our study identified a strong association between

the need for transfusion in the ICU and deteriora-

tion in renal function in the ICU of those patients

who underwent OS. This need for transfusion in

the ICU is indicative of the hemodynamic deteriora-

tion suffered by these patients during surgery,

mainly due to surgical bleeding, with the need for

transfusion both in the operating room and later

in the ICU and an inotropic support. In fact, in the

OS group greater intraoperative bleeding (median

1,000 mL) was observed. Therefore, renal function

in these patients must be intensively observed and

the appropriate treatment adopted to avoid severe

renal failure. Early detection of signs of hypoperfu-

sion is important, including hypertension and levels

of lactate in blood (useful above all in patients who

do not have initial hypertension but already have

tissue hypoxia). Patients should be monitored

closely both during and after surgery in order to

maintain a mean blood pressure of �65 mm Hg,

a central venous pressure between 8 and 12, and

a urine deficit of 0.5-1 mL/kg/hr. To achieve this,

adequate fluid replacement and/or inotropic sup-

port, if necessary, must be carried out to maintain

adequate gas exchange (mixed venous saturation

�70%) and transfusion of compact red blood cells

to maintain adequate hemoglobin levels in the

blood.

518 Garcıa et al. Annals of Vascular Surgery

Table III. Renal exacerbation rate in the two groups

Renal exacerbation rate

ICU Discharge 1 month 6 months 12 months 24 months

OS group 15.3% (n ¼ 9/59) 6.9% (n ¼ 4/58) 3.4% (n ¼ 2/58) 1.7% (n ¼ 1/58) 1.8% (n ¼ 1/56) 2.1% (n ¼ 1/47)

SEF group 3.6% (n ¼ 2/56) 5.4% (n ¼ 3/56) 5.4% (n ¼ 3/56) 3.9% (n ¼ 2/51) 3.9% (n ¼ 2/51) 2.7% (n ¼ 1/36)

p 0.033 0.52 0.483 0.451 0.457 0.682

CONCLUSIONS

Exacerbation of renal function occurred in both

groups independently of treatment type. In the im-

mediate postoperative period, this deterioration was

most frequent in the OS group, probably related to

the hemodynamic deterioration. In follow-up, this

deterioration tended to disappear in both groups, al-

though the Cr figures showed a constant increase in

the SEF group, probably due to the repeated diag-

nostic tests that use contrast and the effect of the

suprarenal fixation stent. Multicenter randomized

prospective studies would be needed to confirm

this hypothesis.

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