Suprarenal Clamping Is a Safe Method of Aortic Control when Infrarenal Clamping Is not Desirable
Article Outline
We evaluated the safety of suprarenal aortic clamping in patients with abdominal aortic aneurysm (AAA) treated by open aortic replacement by retrospectively reviewing all patients who underwent elective AAA replacement at a university hospital from 1993 until 2003. We reviewed 249 patient charts and divided them into three groups according to the clamp location during aortic replacement: group 1, infrarenal clamp group (n = 185); group 2, suprarenal clamp group (n = 52); and group 3, supraceliac clamp group (n = 12). Groups 1 and 2 were compared with respect to risk factors, intraoperative events, and postoperative events. Statistical analysis was done using Wilcoxon's rank-sum test, chi-squared test, and Fisher's exact test. Risk factors were comparable in groups 1 and 2 except for weight, which was higher in group 1. Intraoperative urine output, hypotensive episodes, and use of renal protective drugs were comparable in the two groups. Operation time, blood loss, and use of IV fluids were all significantly higher in group 2, while total aortic clamp time was higher in group 1. Postoperative events were comparable except for postoperative peak creatinine, intensive care unit length of stay, and postoperative length of stay, which were higher in group 2; however, discharge creatinine was comparable without a significant difference. Suprarenal clamping is a safe method of aortic control during open AAA replacement surgery. The selection of clamping site should be individualized according to the intraoperative anatomy. Supraceliac clamping is not necessarily the preferable method of aortic control when the infrarenal location is not suitable for clamping.
Introduction
Suprarenal aortic clamping is needed in approximately 10% of operations for infrarenal aortic aneurysmal disease, especially in patients with juxtarenal aneurysms.1 In this era of endovascular aneurysm repair, most straightforward aneurysms with adequate infrarenal necks are repaired with stent grafts. The traditional open method of repair is predominantly confined to juxtarenal or pararenal aneurysms. The technical complexity of these procedures may be challenging to recently trained young vascular surgeons more experienced with wires and catheters than with open aortic repair. The issue regarding the optimal level for proximal aortic control has been controversial. Various reports have tried to answer whether supraceliac, suprarenal, or interrenal aortic clamping are safe and whether one is superior in terms of lower morbidity and postoperative renal failure.2, 3, 4, 5 Reluctance to clamp the aorta at the suprarenal or supraceliac level to avoid excessive morbidity may lead to overextending infrarenal clamping to diseased aortas. This could lead to intraoperative anastomotic problems with excessive blood loss or later development of para-anastomotic pseudoaneurysms.6
At the University of Iowa Hospitals and Clinics, our practice and preference when the infrarenal aorta is not suitable for clamping has been to clamp suprarenally (between the superior mesenteric artery [SMA] and the renal arteries) or interrenally (between the renal arteries) for juxtarenal aneurysms. In order to evaluate the safety of this approach, we conducted a retrospective review of all the elective open aneurysms repaired from 1993 to 2003 and compared the morbidity and mortality between infrarenal and suprarenal clamping.
Materials and Methods
A retrospective review of the medical records of all patients who underwent elective open aortic replacement for abdominal aortic aneurysm (AAA) between January 1993 and December 2003 was performed. A total of 249 patients were identified and assigned to three groups according to the level of aortic clamping. In group 1, the clamping level was the infrarenal aorta, in group 2 the suprarenal aorta (above one or both renals), and in group 3 the supraceliac aorta. Of the 249 patients, there were 185 (74%) in group 1, 52 (21%) in group 2, and 12 (5%) in group 3.
We excluded all emergency operations for ruptured aneurysms, renal transplant patients, thoracoabdominal aneurysms, concomitant nephrectomies, patients who needed renal artery manipulation (bypass, endarterectomy, and reimplantation) in the infrarenal group, and cases where clamping was performed above an accessory renal artery.
The decision was made to leave group 3 out of our statistical analysis due to the low number of patients in this group and the fact that aneurysms in this group were all suprarenal or at the visceral level requiring supraceliac clamping.
The data gathered for analysis were divided into preoperative clinical data (Table I), intraoperative data (Table II), and postoperative data (Table III).
Table I. Preoperative clinical data
| Variable | Infrarenal | Suprarenal | p |
|---|---|---|---|
| Age (years) ± SD | 70.4 ± 9 | 72.5 ± 8.1 | 0.128 |
| Sex (male) | 140 (76%) | 29 (56%) | 0.005 |
| Median weight (kg) (IQR) | 80 (69-97) | 78 (64.9-86.3) | 0.039 |
| Tobacco use (current) | 67 (36.2%) | 15 (28.9%) | 0.324 |
| Hypertension | 77 (41.6%) | 25(48.1%) | 0.406 |
| CAD | 123 (66.5%) | 31 (59.6%) | 0.359 |
| CHF | 26 (14.1%) | 8 (15.4%) | 0.809 |
| Hyperlipidemia | 143 (77.3%) | 42 (80.8%) | 0.593 |
| COPD | 61 (32.8%) | 14 (26.9%) | 0.407 |
| RI | 32 (17.3%) | 11 (21.2%) | 0.524 |
| Median creatinine (IQR) | 1.2 (1.0-1.4) | 1.1 (0.9-1.5) | 0.601 |
| Dialysis | 5(2.7%) | 0 | 0.231 |
| Diabetes | 20 (10.8%) | 7 (13.5%) | 0.595 |
| Median aneurysm size (cm) (IQR) | 6 (5-7) | 6 (5-7) | 0.263 |
| Preoperative ASA | 104 (56.2%) | 36 (69.2%) | 0.092 |
| Preoperative β-blockers | 95 (51.4%) | 34 (65.4%) | 0.073 |
Table II. Intraoperative data
| Variable | Infrarenal | Suprarenal | p |
|---|---|---|---|
| Median total aortic clamp time (min) (IQR) | 55.5 (44.5-72) | 45 (30-64) | 0.006 |
| Suprarenal clamp time (n = 32/52) | 27 | ||
| Median operative time (IQR) | 270 (225-320) | 300 (248-382) | 0.025 |
| Median EBL (mL) (IQR) | 1,000 (700-1,600) | 1,225 (775-2,000) | 0.033 |
| Median intraoperative fluids (IQR) | 4,000 (3,000-5,300) | 4,800 (3,750-6,400) | 0.007 |
| Median urine output (IQR) | 547 (305-900) | 550 (400-968) | 0.474 |
| Renal drip | 84 (45%) | 26 (50%) | 0.557 |
| Hypotension | 112 (60%) | 38 (73%) | 0.098 |
| Intraoperative RBC (units) | |||
 0 | 67 (36.2%) | 5 (9.6%) | |
| 1 | 32 (17.3%) | 9 (17.3%) | |
| 2 | 41 (22.2%) | 15 (28.9%) | <0.0001 |
| 3 | 22 (11.9%) | 10 (19.2%) | |
| 4 | 10 (5.4%) | 4 (7.7%) | |
| 5-16 | 13 (7.0%) | 9 (17.3%) | |
| Intraoperative platelets (units) | |||
| 0 | 180 (97.3%) | 50 (96.2%) | |
| 1 | 4 (2.2%) | 1 (1.9%) | 0.856 |
| 2 | 1 (0.5%) | 1 (1.9%) | |
| Intraoperative FFP (units) | |||
| 0 | 175 (94.6%) | 48 (92.3%) | |
| 1-3 | 7 (3.8%) | 2 (3.8%) | 0.540 |
| 4-7 | 3 (1.6%) | 2 (3.8%) | |
| Surgical approach | Retro 14.1% | Retro 32.6% | 0.004 |
| Trans 85.9% | Trans 67.4% | ||
| Graft used | Bifurcated 30% | Bifurcated 32.6% | 0.741 |
| Tube 70% | Tube 67.4 | ||
| Renal vein ligation | 2 (1.08%) | 10 (19.2%) | <0.0001 |
Table III. Postoperative clinical data
| Variable | Infrarenal | Suprarenal | p |
|---|---|---|---|
| Mortality | 3 (1.6%) | 0% | 1.0 |
| SICU LOS (days) | |||
| 0-1 | 47% | 33% | |
| 2 | 26% | 29% | |
| 3 | 12% | 15% | 0.044 |
| 4-7 | 11% | 17% | |
| >7 | 4% | 6% | |
| Median postoperative LOS (days) (IQR) | 7 (6-11) | 9 (7-12.5) | 0.038 |
| Median peak creatinine (IQR) | 1.2 (1.0-1.6) | 1.4 (1.1-2.2) | 0.023 |
| Median discharge creatinine (IQR) | 1.1 (0.9-1.4) | 1.2 (1.0-1.5) | 0.272 |
| Hypotension | 53 (28.6%) | 16 (30.8) | 0.766 |
| CHF | 9 (4.9%) | 4 (7.7%) | 0.49 |
| MI | 5 (2.7%) | 1 (1.9%) | 1.0 |
| Pneumonia | 12 (6.5%) | 2 (3.9%) | 0.74 |
| Reintubation/tracheostomy | 6 (3.2%)/0% | 3 (5.8%)/1 (1.9%) | 0.41/0.22 |
| Dialysis | 6 (3.2%) | 0% | 0.34 |
| Postoperative RBC (units) | |||
| 0 | 118 (63.8%) | 27 (51.9%) | |
| 1 | 15 (8.1%) | 5 (9.6%) | |
| 2 | 31 (16.8%) | 7(13.5%) | 0.060 |
| 3-5 | 15 (7.6%) | 9 (17.3%) | |
| 6+ | 7 (3.8%) | 4 (7.7%) | |
| Postoperative platelet (units) | |||
| 0 | 180(97.3%) | 47(90.4%) | |
| 1 | 3 (1.6%) | 2 (3.9%) | |
| 2 | 1 (0.5%) | 3 (5.8%) | 0.026 |
| 3+ | 1 (0.5%) | 0 (0.0%) | |
| Postoperative FFP (units) | |||
| 0 | 173 (93.5%) | 44 (84.6%) | |
| 1-3 | 7 (3.9%) | 4 (7.7%) | 0.047 |
| 4-6 | 7 (3.9%) | 4 (7.7%) | |
| 7+ | 1 (0.5%) | 0 (0.0%) |
Statistical analysis was done using Wilcoxon's rank-sum test, chi-squared test, and Fisher's exact test.
Results
Preoperative Data
All preoperative data were analyzed and compared between the two groups. No significant difference was found except for preoperative weight and gender. All variables are summarized in Table I.
Intraoperative Data
The median total aortic clamping time was 55.5 min for the infrarenal group and 45 min for the suprarenal group . This time difference was statistically significant, p < 0.006. In 32 patients in group 2, the suprarenal clamp time was clearly recorded. In these patients, the median suprarenal clamp time was 27 min. Operative time, estimated blood loss, intraoperative fluid requirement, and blood (packed red blood cells) transfusion were all higher in the suprarenal group (group 2); and these values reached statistical significance. Other variables were without any statistical significance (Table II).
In terms of the operative technique (Fig. 1), 86% of patients in group 1 underwent a transperitoneal approach vs. 67% in group 2. The rest were done via a retroperitoneal approach. No difference was found regarding the use of bifurcated versus tube grafts on comparing the two groups.
In the infrarenal group, there were two occasions where the left renal vein required ligation. In the suprarenal group, 10 patients required renal vein ligation to obtain proximal control.
With respect to intraoperative complications, two patients in group 1 had significant intraoperative bleeding due to venous injury. Two other patients had thromboembolism to the lower extremities at the end of the procedure, requiring embolectomy with successful results. In group 2, three patients had significant bleeding: one due to venous injury, one due to arterial bleeding requiring reexploration 1 hr postoperatively, and one due to a splenic injury requiring splenectomy. One patient had thromboembolism to the lower extremities.
Postoperative Data
The perioperative mortality was 1.6% (three patients) in group 1 and 0% for group 2. Two patients in group 1 died, one due to sepsis and multiorgan failure and one due to cardiac arrhythmia.
With respect to the incidence of postoperative renal failure, the peak creatinine value during hospitalization and the discharge creatinine were compared in the two groups. The median peak creatinine was higher in the suprarenal group, but the median discharge creatinine was similar, without a statistically significant difference. Postoperative dialysis was required in six patients (3.2%) in group 1 and none in group 2.
We also looked at the effect of renal vein ligation in group 2 compared to the rest of the patients in that group (ie, group 2). In 10 patients (19%), no significant difference with regard to postoperative peak creatinine and discharge creatinine was found (p = 0.211 and 0.425, respectively). None of these patients had the vein reanastomosed.
The surgical intensive care unit (SICU) length of stay (LOS) and the overall hospital LOS were longer for the suprarenal group, both reaching statistical significance. All other complications and outcomes are detailed in Table III.
Discussion
Endovascular repair of AAA has become a routine practice. Currently, approximately 60% of infrarenal AAAs are candidates for repair with endovascular techniques, and this number is expected to increase with the development of newer endografts.7 Open surgery may become limited to juxta- and suprarenal aneurysms and explants after endograft failure. These procedures will require clamping of the aorta at the suprarenal or supravisceral segment.
The site of aortic clamping (supraceliac vs. suprarenal) has been a matter of debate throughout the vascular literature over the last 20 years with regard to postoperative morbidity and mortality.
In a study by Green et al.8 comparing the outcome between supraceliac and suprarenal clamping, the rates of operative mortality were higher in the suprarenal group (32% vs. 3%) and the rate of renal failure was also higher (23% vs. 3%). They attributed their results to the greater likelihood of dislodging atherosclerotic debris in the pararenal aorta than in the supraceliac aorta, which usually has fewer atherosclerotic plaques.
Other authors have advocated the use of supraceliac clamping. Shneider et al.9 reported their experience with 23 patients who required supraceliac clamping for juxtarenal AAA. No supraceliac clamp patient required dialysis, although 26% had a transient azotemia compared to 12% in the infrarenal control group. There were no operative deaths, and no patient suffered clinical hepatic failure or intestinal ischemia.
Hines and Chorost10 reported no instances of bowel ischemia, no significant deterioration of postoperative renal function, and no dialysis in a group of 16 patients who underwent supraceliac clamping for pararenal aortic aneurysms but found that interrenal clamping (between the renal arteries) was associated with increased incidence of renal failure.
Some authors9, 10, 11 recommend clamping of the supraceliac aorta to avoid retraction and manipulation of large aneurysms that may reduce the risk of embolization during dissection. It is believed this approach may avoid the ligation of the left renal vein in large juxtarenal aneurysms to facilitate suprarenal control.
Other authors advocate the suprarenal (between the SMA and the renals) clamp location vs. supraceliac clamping. In a recent retrospective review by Sarac et al.12 comparing supraceliac vs. suprarenal clamping for juxtarenal aneurysms, the mortality rate was greater for the supraceliac group (11.6% vs. 2.1%). In addition, the supraceliac group had a significantly greater rate of renal insufficiency (41.9% vs. 22.1%).
Back et al.13 also found similar results in a retrospective review of their experience with visceral aneurysms. In this series, the perioperative mortality varied for clamp locations [infrarenal 2.1%, suprarenal 3.0%, supravisceral (above the celiac or superior mesenteric artery) 10.8%].
We have not found suprarenal clamping to be associated with increased morbidity. We have tried to minimize the number of vessels involved during cross-clamping. Very often, one renal artery is located higher than the other and an aortic clamp may be safely applied between the two renal arteries, thus limiting the ischemia to one kidney. One key issue is patient selection.
When clamping above the renal arteries is anticipated based on the computed tomographic scan, our approach has typically been to use a retroperitoneal approach when the aneurysmal disease is limited to the aorta or proximal common iliac arteries. When the aneurysmal disease extends significantly into the right common iliac artery and its bifurcation, we prefer to use the transabdominal approach. An essential part of the suprarenal control in the transperitoneal approach is adequate mobilization of the renal vein. Ligation of the left gonadal and lumbar veins will allow for significant cephalad mobilization of the renal vein. Division of the left adrenal vein will allow for significant caudal mobilization of the renal vein. Occasionally, the aneurysmal dilatation is extensive at the level of the renal vein and is associated with a significant inflammatory reaction. In this situation, division of the renal vein will be necessary to provide adequate exposure above the renal arteries. If division of the left renal vein is contemplated, the left adrenal, lumbar, and gonadal veins should be preserved to provide venous drainage from the renal vein. If division of the renal vein after these branches have been ligated becomes necessary, then the renal vein can be divided between two vascular clamps and reattached once the proximal aortic anastomosis is completed. In our study this approach was found to be safe, as demonstrated above with no significant difference in postoperative creatinine levels with renal vein ligation.
The retroperitoneal approach will allow avoidance of the left renal vein, especially when the left kidney is mobilized anteriorly and the dissection plane is carried posterior to it. The retroperitoneal exposure of the suprarenal area is further enhanced by dividing the left crus of the diaphragm. The clamping site is carefully assessed prior to applying the clamp. Suprarenal or interrenal clamping is avoided if that segment is aneurysmal or contains an intraluminal thrombus as this could lead to fragmentation and embolization of thrombus material into the renal or visceral vessels while the clamp is applied or once the clamp is removed and applied distal to the proximal anastomosis. In such situations, clamping in the supraceliac location will be preferred.
Familiarity with supraceliac clamping remains essential, especially for aortic control during ruptured aortic aneurysm repairs and the repair of endoleak where a device with suprarenal fixation has been used. The disadvantages of supraceliac clamping include increased visceral ischemia with potential coagulopathy, increased cardiac afterload, and a higher degree of hypotension upon clamp release. Back-bleeding from the celiac artery and the SMA can be managed by using an intra-aortic occlusive balloon.
At our institution we clamp at the suprarenal level preferentially over the supraceliac location, as long as the condition of the aorta allows it. Good selection of the clamp level according to the condition of the aortic tissue is perhaps the key factor in avoiding technical complications such as visceral embolism, aortic tearing or dissection, incomplete inflow control, and intraoperative bleeding. Also, incorrectly chosen cross clamp level with later reclamping at a higher level has been associated with increased morbidity, especially atheroembolic complications.8
In our retrospective review, our mortality rate was 0% with minimal cardiac comorbidities, e.g., myocardial infarction (1.9%), and no patients required postoperative dialysis due to renal failure (0%).
The perception that suprarenal clamping exposes the patient to greater risks, increased perioperative morbidity due to potential renal failure, and greater hemodynamic changes is unfounded.
The reported incidence of postoperative renal failure after suprarenal clamping ranges 14-50%.5, 15, 16 The etiology of the renal failure is likely multifactorial, but several factors appear to be consistent throughout the literature. The first one is the presence of preoperative renal insufficiency.12, 15, 16 The second and probably most important is suprarenal aortic clamp time.17, 18, 19 In a retrospective study, Wahlberg et al.15 reviewed 60 patients who underwent infrarenal aortic reconstruction with temporary suprarenal clamping. The preoperative creatinine level was 1.21 mg/dL (±0.54) and the clamp time duration was 32 min (±17 min). They observed only transient azotemia in 23% of patients. None needed dialysis. The main determinant of azotemia was total renal ischemia time, with a 10-fold increased risk when suprarenal aortic clamping was >50 min. In addition, intraoperative hypotension has been correlated with postoperative renal insufficiency.12, 13, 14, 15
In our study, variables that could affect the perioperative renal morbidity were analyzed in both groups. Preoperative risk factors such as renal insufficiency, diabetes, and previous use of dialysis were similar between the groups. Factors such as hypotension during surgery, use of renal drip (mannitol, furosemide [Lasix], dopamine), and intraoperative urine output were also similar between groups 1 and 2.
The total aortic clamping time was longer in the infrarenal group. In the suprarenal group, our median total clamp time was 45 min, with a renal cross-clamp time of 27 min in 32 of our patients. Unfortunately, for 20 patients only total aortic clamp time was recorded. Nevertheless, no patients in the suprarenal clamp group had severe renal insufficiency postoperatively, with no patients requiring dialysis and a median discharge creatinine of 1.2 mg/dL.
Other groups have reported similar results. Giulini et al.20 compared suprarenal clamping for juxtarenal aneurysms and infrarenal clamping for regular AAA. Their perioperative mortality was 3.6% for the suprarenal group vs. 1.9% for the infrarenal one, which did not represent a statistically significant difference. In their study, renal function deteriorated in 14% (suprarenal group) vs. 0% (infrarenal group) but only 2% required dialysis. They also concluded that suprarenal clamping can be performed with low risk.
Conclusion
Suprarenal clamping is a safe method of aortic control during open AAA replacement surgery. The selection of clamping site should be individualized according to the intraoperative anatomy. Supraceliac clamping is not necessarily the preferable method of aortic control when the infrarenal location is not suitable for clamping.
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PII: S0890-5096(08)00076-9
doi:10.1016/j.avsg.2008.02.006
© 2008 Annals of Vascular Surgery Inc. Published by Elsevier Inc All rights reserved.
