Annals of Vascular Surgery
Volume 22, Issue 1 , Pages 1-4, January 2008

Renal Response to Open and Endovascular Repair of Abdominal Aortic Aneurysm: A Prospective Study

  • M. Gawenda

      Affiliations

    • Corresponding Author InformationCorrespondence to: Michael Gawenda, MD, Division of Vascular Surgery, Medical Center, University of Cologne, Kerpener Str. 62, 50937 Cologne, Germany
    • ,
  • J. Brunkwall

Division of Vascular Surgery, Medical Center, University of Cologne, Cologne, Germany

published online 04 December 2007.

Article Outline

Because of incompatible reports about the renal impairment to abdominal aortic aneurysm (AAA) repair, we conducted a prospective study to determine the differences in renal response between open (OR) and endovascular (EVAR) aneurysm repair. In a prospective, nonrandomized, single-center study, we evaluated 485 patients with AAAs undergoing OR or EVAR between January 2000 and December 2005. Only electively performed procedures were analyzed in detail. The OR group included 229 patients (males/females 203/26, median age 69.8 [range 43-90] years, aneurysm diameter in median 57 [26-95] mm), and the EVAR group integrated 144 patients (males/females 129/15, 73.1 [49-90] years [p=.001], 55 [33-100] mm). Renal function was assessed by determinating the preoperative serum creatinine (SCr) level and SCr clearance according to Cockcroft-Gault. Postoperatively, SCr level and SCr clearance were determined at defined intervals, reported as highest postoperative SCr level, SCr level at time of discharge, lowest postoperative SCr clearance, and SCr clearance at time of discharge. The parameters of height, weight, diabetes, smoking habit, serum cholesterol level, and hemoglobin were not different between the groups. Significantly different were the American Society of Anesthesiologists classification, the Society for Vascular Surgery Comorbidity Score, and the exposure to contrast dye. Moreover, significantly different were intraoperatively measured median blood loss (1,200 vs. 400 mL) and the median time of operation (164 vs. 135 min). Although, the preoperative SCr levels between the groups were not statistically different (OR group 1.0 [0.87-1.23] mg/dL [median, interquartile range], EVAR group 1.0 [0.9-1.3]; p > 0.05), the SCr clearance was (OR group 72.8 [58.2-98.8] mL/min, EVAR group 67.6 [51.3-85.1] mL/min; p = 0.007). In the postoperative period, SCr level did not change significantly in the OR group but did in the EVAR group to a level of 1.08 (0.9-1.36) mg/dL (p = 0.007). Similarly, SCr clearance decreased significantly in the EVAR group to a level of 66.7 (49.9-81.4) mL/min. These results were influenced by the stent graft design (deployment under the renal arteries vs. covering the renals with bared stents). Mortality was 3/229 in the OR group and 4/144 in the EVAR group. Acute renal impairment occurred in a subset of patients with AAAs with regard to the type of repair. EVAR showed a slight deterioration of renal function, but the evaluated tests are insensitive and without prognostic value concerning mortality or hospitalization. More sensitive markers of the differentiated renal functions (cystatin C for renal glomerular function, N-acetyl-ß-d-glucosamidase for proximal tubular function) should be evaluated in future studies.

 

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Introduction 

Acute renal dysfunction after open repair of abdominal aortic aneurysm (AAA) has a reported prevalence up to 13.9%1 and remains a major cause of increased mortality.2, 3 Furthermore, this condition is associated with prolonged length of stay.4 Even though aortic cross-clamping is placed infrarenally, decline in renal perfusion with a redistribution of the renal blood flow toward the cortical compartment is induced. Moreover, humoral and neurogenic factors seem to be responsible for the multifactorial etiology of the renal impairment in open infrarenal aortic procedures.5, 6

Endovascular aortic aneurysm repair (EVAR) offers a less invasive alternative to open repair, avoiding aortic cross-clamping and offering less perioperative hemorrhage7 but the potential nephrotoxicity of the administered contrast medium has to be considered.8, 9, 10 In addition, intra-aortic manipulation with guidewires, catheters, and introducer sheaths may lead to disruption of lipid-laden plaques and subsequent embolization into the renal arteries.11, 12

This study was undertaken to evaluate the renal response to the different techniques of open and endovascular repair of AAA.

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Materials and Methods 

A prospective, single-center, nonrandomized study was conducted to evaluate the renal response to open repair and EVAR in infrarenal aortic aneurysms. Patient enrollment began in January 2000 and was completed in December 2005. The treatment method (open repair [OR], endovascular aneurysm repair [EVAR]) used as well as the stent graft devices were decided according to the preference of the surgeons involved (M. G., J. B.) based on the morphology of the aortic and iliac vessels, in accordance with accepted guidelines.13

Assessment of renal function included measurement of serum creatinine (SCr) concentration preoperatively as well as postoperatively before discharge. Creatinine clearance, according to the Cockcroft-Gault formula, was calculated each time for all patients.

Analyses were restricted to patients undergoing elective repair of AAA; patients with urgent repair due to symptomatic aneurysms or ruptured aneurysms were excluded. Also, patients with suprarenal aneurysm involvement, suprarenal cross-clamping, and renal artery revascularization were excluded.

Renal impairment was described as change of SCr level and creatinine clearance in both treatment groups (median, range). Renal dysfunction was defined as clinically significant if the rise in SCr level exceeded the baseline value by 25% or the creatinine clearance decreased by 25%.

Statistical evaluation was done by descriptive statistics (mean and median with lower and upper quartiles). Test statistics were performed with both the t-test and the Mann-Whitney U-test. p < 0.05 was considered significant. All evaluations were performed using the statistical package SPSS for MS-Windows, release 12.0 (SPSS, Chicago, IL).

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Results 

A total of 485 patients (males/females 420/65, age 71.7 [43-91] years, aneurysm diameter 58 [23-110] mm) were treated. There were 373 procedures carried out electively. Transperitoneal OR was performed in 229 patients (males/females 203/26, 69.8 [43-90] years, 57 [26-95] mm). In 144 patients (129/15, 73.1 [49-90], 55 [33-100] mm) the aneurysms were excluded endovascularly. Patients' characteristics are given in Table I.

Table I. Patient characteristics by elective repair
CharacteristicsOREVAR
Males/females203/26129/15
Age (years)a69.8 (62.9-75.4)73.4 (68.0-79.3)
Body mass indexa26.0 (24.0-28.7)26.6 (24.1-28.6)
Hemoglobin (g/L)14.2 (13.2-15.2)14.1 (12.6-15.0)
Smoker77%57%
Serum cholesterol >200 mg/dL42%42%
Diabetes11%14%
SVS comorbidity scorea6 (4-10)12 (8-15)
ASA 1, 235%23%
ASA 3, 4, 565%77%
Procedure time (min)a165 (121.5-210.0)135 (113-169)
Blood loss (mL)a1200 (700-1,800)400 (200-600)
Mortality1.3%2.8%
Length of stay postoperatively (days)a9 (7-13)7 (5-8)

SVS, Society for Vascular Surgery; ASA, American Society of Anesthesiologists.

aMedian, lower and upper quartiles.

In the cohort of electively performed endovascular procedures, suprarenal fixation of the stent graft was achieved in 84 (58%) patients. Patients´ characteristics did not differ when comparing those who had infrarenal stent grafts with those who had suprarenal fixation.

The preoperative renal function tests revealed no significant differences between preoperative SCr levels of the OR and EVAR groups (Table II). However, preoperative creatinine clearance showed a significant difference between the treatment groups (p = 0.013).

Table II. Renal function tests, OR vs. EVAR group
TestsOREVAR
Preoperatively
SCr level (mg/dL)a1.0 (0.87-1.23)1.0 (0.9-1.3)
Creatinine clearance (mL/min)72.8 (58.2-98.8)67.6 (51.3-85.1)
At discharge
SCr level (mg/dL)0.98 (0.83-1.23)1.08 (0.9-1.36)
Creatinine clearance (mL/min)74.6 (57.8-95.9)66.7 (49.9-81.4)

aMedian, lower and upper quartiles.

Evaluation of the SCr level at discharge was not altered significantly in the OR group, but in the EVAR group the increase of SCr level reached significance (p = 0.007); in the same way, creatinine clearance worsened significantly in the EVAR group (p = 0.032). The change of creatinine clearance in the OR group was not significant (p = 0.25).

The influence of suprarenal fixation of the stent grafts in the EVAR group was analyzed additionally (Table III). The pre- to postoperative change in SCr level was not significant in the infrarenal EVAR group (p = 0.1), nor was the altered creatinine clearance (p = 0.95). However, in the EVAR group with suprarenal stent graft fixation, the slight changes in SCr level (p = 0.027) as well as in creatinine clearance (p = 0.015) reached significance.

Table III. Renal function tests, EVAR group with infrarenal stent grafts (n = 60) vs. EVAR group with suprarenal fixation (n = 84)
TestsEVAR infrarenalEVAR with suprarenal fixation
Preoperatively
SCr level (mg/dL)a1.09 (0.93-1.3)1.0 (0.86-1.3)
Creatinine clearance (mL/min)63.03 (50.17-77.62)70.70 (51.5-90.79)
At discharge
SCr level (mg/dL)1.09 (0.91-1.45)1.07 (0.9-1.32)
Creatinine clearance (mL/min)66.82 (49.59-80.66)65.9 (50.97-82.42)

aMedian, lower and upper quartiles.

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Discussion 

Renal dysfunction has a predictive value to the perioperative course in thoracic as well as abdominal aortic aneurysm repair. Mortality due to acute renal dysfunction after open AAA repair can be as high as 27.8%.2 On the other hand, a decline in kidney function after the administration of a contrast medium is associated with a prolonged hospital stay, adverse cardiac events, and high mortality both in the hospital and in the long term.14 Therefore, it seems worthwhile to evaluate the response of renal function to the manner of aneurysm repair. Although the Dutch Randomized Endovascular Aneurysm Management (DREAM) trial showed that postoperative changes in SCr level were similar in patients undergoing EVAR and OR, several trials have confirmed that after EVAR the renal damage is less compared to OR.15, 16 In the face of these conflicting results we conducted a prospective trial to evaluate the renal response to OR and EVAR. Both cohorts showed similarities, especially in their demographics, and some differences, particularly in their risk profile; but still the groups were comparable. In the OR group no renal impairment could be documented and neither SCr level nor the more sensitive creatinine clearance showed any significant changes. On the other hand, in the EVAR group SCr as well as creatinine clearance showed slight postoperative renal impairment. In contrast to the literature, which revealed no influence of suprarenal fixation of stent grafts,17, 18, 19, 20, 21 our subgroup analysis showed a slight renal impairment in the EVAR group only in those patients with suprarenal fixation. The cause of this renal impairment during the short postoperative period is speculative, but it may have resulted from contrast damage, procedural atheroemboli, or continued renal injury from the suprarenal stent.12, 17

As a limitation of our study, the lack of data on the exact doses of contrast media has to be mentioned. Because of diagnostic procedures being performed outside for part of our treatment groups, the amount of contrast dye could not be calculated; but differences in the volume of contrast media might not explain the discrepancy in the EVAR group because the time interval between the applications is regularly too long.

Moreover, the interval between the contrast-enhanced computed tomography and the preoperatively performed angiographic studies in several patients was highly variable. Therefore, the effect of the repetitive contrast media exposition in the EVAR group has to be speculative. In addition, the possible effect of other nephrotoxic medications may be uncertain because their application in the prehospital period was not fully documented.

Beyond these aspects, our study revealed the necessity to take preoperative renal impairment into consideration as an indication for suprarenal stent graft fixation. However, in future studies more sensitive markers of the differentiated renal functions (cystatin C for renal glomerular function, N-acetyl-ß-d-glucosamidase for proximal tubular function) should be evaluated.

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References 

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PII: S0890-5096(07)00313-5

doi:10.1016/j.avsg.2007.07.027

Annals of Vascular Surgery
Volume 22, Issue 1 , Pages 1-4, January 2008

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