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Eur J Cardiothorac Surg 1998;14:201-205
© 1998 Elsevier Science NL

Reduced renal failure following thoracoabdominal aortic aneurysm repair by selective perfusion¹

^a Department of Vascular Surgery, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands
^b Department of Cardiopulmonary Surgery, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands
^c Department of Anesthesiology, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands

Received 19 January 1998; received in revised form 28 April 1998; accepted 12 May 1998.

Corresponding author. Department of Vascular Surgery, Academic Medical Center, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands. Tel.: +31 20 5662766; fax: +31 20 6914858; e-mail: m.jacobs@amc.uva.nl

	Abstract

Top Abstract Introduction Patients and methods Results Discussion Appendix A. Conference... References

 
Objectives: Renal failure and visceral ischemia are feared complications following thoracoabdominal aortic aneurysm (TAAA) repair, significantly contributing to mortality. This prospective study describes volume- and pressure-controlled perfusion of the renal and visceral arteries during TAAA surgery. Methods: In 73 consecutive patients (mean age 59 years), TAAA repair (27 type I, 28 type II, 8 type III and 10 type IV) was performed, using retrograde and selective organ perfusion. Sixteen patients had impaired renal function with blood creatinine higher than 100 mmol/l. During the thoracic part of the procedure, the mean distal aortic pressure was kept above 60 mm Hg by means of left-heart bypass. After opening the abdominal aorta, the renal and visceral arteries were individually perfused by means of perfusion catheters (9 French) in the first 33 patients (group I). Volume flow through each catheter was assessed with ultrasound flow meters and maintained at least at 60 ml/min. In addition to volume flow measurements, catheters with pressure sensors were used in the last 40 patients (group II), allowing pressure-controlled selective perfusion. The extent of the aneurysm was comparable in both groups. Results: Mean cross-clamp time for the thoracic part was 46 min, including proximal anastomosis and reattachment of intercostal arteries. Mean cross-clamp time for the abdominal part was 74 min, including re-implantation of intestinal and renal arteries and selective dacron grafts to the celiac-axis arteries (n=5), superior mesenteric arteries (n=8) and renal arteries (n=25), through which the catheters guaranteed continuous perfusion during the time the anastomosis was performed. Urine output was uninterrupted in all patients, irrespective of cross-clamp time. In group I, one patient (3%) developed renal failure and three patients (9%) required temporary peritoneal dialysis. In group II, no patients developed renal failure and two patients (5%) required temporary peritoneal dialysis. Thirteen patients with pre-existing renal impairment did not deteriorate. No patients developed visceral ischemia or multiple-organ failure. Total in-hospital mortality was 6/73 (8%) and was related to cardiopulmonary complications. Conclusions: Renal and visceral ischemia can be reduced significantly by continuous perfusion during cross-clamping in TAAA repair. Not only sufficient volume flow but also adequate arterial pressure appears to be essential in maintaining renal function.

Key Words: Thoracoabdominal aortic aneurysm repair • Selective perfusion

	Introduction

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The expected outcome of thoracic and thoracoabdominal aortic aneurysm (TAAA) repair has improved during the last decade, mainly as a result of a clearer understanding of the determinants of the operative risks and the major postoperative complications such as paraplegia, renal failure, and visceral ischemia. Surgical adjuncts to decrease renal failure include perfusion of the renal arteries with cold Ringer's lactate solution and various methods of blood perfusion to the kidneys [1] [2]; however, clinical studies have not shown protective effects [3] [4]. Recently, we described retrograde and selective organ perfusion as a safe technique to prevent ischemic renal and intestinal damage during cross-clamping of the aorta in TAAA repair [5]. The most convincing value of this technique was the uninterrupted urine output in all patients, irrespective of aortic cross-clamp time. However, three patients (9%), who all had impaired renal function before surgery, had further increased creatinine levels and one patient (3%) developed renal failure. This implied that the technique of selective organ perfusion was not adequate to prevent renal failure in patients with preoperatively impaired renal function. Since we only assessed volume flow in each perfusion catheter, we hypothesized that the perfusion pressure in the renal arteries was insufficient.

This prospective study describes the results of pressure-controlled selective perfusion of the renal and visceral arteries during TAAA surgery.

	Patients and methods

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In 73 consecutive patients, TAAA repair was performed, using retrograde and selective organ perfusion. Mean age was 59 years (range 21–83). There were 46 men and 27 women. Fifteen patients had chronic aortic dissection, 13 had a symptomatic aneurysm, and four suffered from rupture and were operated on as an emergency. Forty-six patients (63%) had hypertension, 26 (36%) chronic obstructive pulmonary disease, 19 (26%) previous myocardial infarction, 16 (22%) impaired renal function with blood creatinine higher than 100 mmol/l, and 14 (19%) previous infrarenal aortic surgery. Smoking was an associated risk factor in 41 patients (56%). Fig. 1 depicts the extent of the aneurysm for the whole group of patients.

View larger version (22K): [in this window] [in a new window]   Fig. 1. Extent of thoracoabdominal aortic aneurysm in 73 patients, based on the classification of E.S. Crawford.

Retrograde aortic perfusion was achieved by cannulation of the left atrium or pulmonary vein and the femoral artery, using a centrifugal pump. Patients received heparin 0.5 mg/kg. Retrograde aortic perfusion was performed only when the aneurysm did not extend below the renal arteries (TAAA I). In these patients, the aorta was cross-clamped, using two clamps, followed by complete transection of the aorta and performance of the proximal anastomosis. Meanwhile, retrograde aortic perfusion maintained visceral and spinal-cord perfusion with a mean distal aortic pressure of at least 60 mm Hg. Based on urine output and motor-evoked potentials, the critical perfusion pressure (femoral-artery line) was increased when necessary. Intercostal arteries between T8 and T12 were routinely reattached, followed by performance of the distal anastomosis. Multiple-organ perfusion was installed in type-II, type-III, and type-IV aneurysms after opening the abdominal aorta by means of perfusion catheters (9 French), which were inserted in the celiac-axis, superior mesenteric, and both renal arteries, and connected to the left-heart bypass system.

The aortic island containing the visceral arteries was then anastomosed around the perfusion catheters. Thus, the ischemic time consisted only of the time required to perform the aortotomy, to insert the perfusion catheters, and to disconnect the system just before the last aortic stitches, which is usually not more than a few minutes. In general, the celiac-axis, superior mesenteric, and both renal arteries were reattached to the dacron graft. However, in case of concomitant disease of these arteries (aneurysm, ostial stenosis, or occlusion) or a sludgy aortic wall, separate grafting was performed, using 8-mm dacron grafts (Sulzer Vascutek®, Scotland). In 16 of the 73 patients, we performed 38 separate grafts, 25 to the renal arteries, five to the celiac-axis arteries, and eight to the superior mesenteric arteries. Although these arteries were separately grafted, continuous perfusion was guaranteed by means of the perfusion catheter inserted in the target artery through the 8-mm graft, which was anastomosed end-to-end around the catheter. After completion of the anastomosis, the tip of the perfusion catheter was withdrawn into the graft and perfusion was continued until reimplantation of the graft into the tube graft.

In the first 33 patients (group I), volume flow (ml/min) through each catheter was assessed with ultrasound flow meters (Transonic®, Ithaco, New York) and kept at at least 60 ml/min [5]. In addition to volume-flow measurements, perfusion catheters with pressure sensors (Medtronic DLP®, Grand Rapids, MI) were used in the next 40 patients (group II), allowing pressure-controlled selective perfusion. Extent of the aneurysm was comparable in both groups. Blood creatinine (mmol/l) was measured before surgery and daily until the 10th postoperative day.

Mean cross-clamp time for the thoracic part of the procedure was 46±4 min, which includes 5 min for assessment of motor-evoked potential changes, transection of the aorta, performance of the proximal anastomosis, reattachment of the intercostal arteries, and performance of the distal anastomosis in type-I aneurysms.

Mean cross-clamp time for the abdominal part was 74±4 min, consisting of insertion of the multiperfusion system, reattachment of the visceral arteries, separate grafting of the renal and intestinal arteries (n=38), performance of the distal anastomosis, reattachment of the lumbar arteries based on motor-evoked potentials, attachment of separate grafts to the tube graft, and an additional bifurcated graft for iliac aneurysm disease in 12 patients.

Mean total extracorporeal perfusion time calculated from cannulation until decannulation was 149±12 min. Mean selective perfusion time through the multiperfusion system was 64±6 min for the celiac-axis, 63±5 min for the superior mesenteric, and 72±6 min for the renal arteries.

	Results

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General outcome
All 73 patients survived the surgical procedure and immediate postoperative care was performed in the intensive-care unit. The main complications are listed in Table 1. There were no significant differences between patients in group I and group II. Atelectasis and pneumonia were the most important postoperative problems (73%). Arrhythmia (20%) and myocardial infarction (3%) were the most common cardiac complications. Paraplegia occurred in four patients; one in type II, one in type III, two in type IV (5%). Mortality was mainly due to cardiopulmonary complications (8%). No complications relating to the left-heart bypass and multiperfusion catheter system occurred.

Minimal volume flow in patients of groups I and II through each artery was 60 ml/min with a maximum of 210 ml/min. In group II, the minimal arterial pressure at the tip of the catheter was 60 mm Hg. However, to achieve this, it was always necessary to diminish flow and pressure to the femoral artery in favor of selective perfusion. In hypertensive patients and in patients with preoperative renal impairment, the mean selective perfusion pressure in order to maintain urine output was 85 mm Hg. These values were not measured in group I. However, appreciating the necessary adjustments in order to achieve these high pressures in group II, it was obvious that the pressures in group-I patients must have been significantly lower.

Table 2 depicts renal outcome in patients belonging to groups I and II. In group I, four patients (12%) had preoperative renal impairment. One of them developed complete renal failure whereas two with pre-existing renal impairment and one without renal disease developed temporary renal insufficiency, which was treated with peritoneal dialysis with a mean duration of 3 days, whereafter normal recovery evolved.

There was no clinical evidence of any visceral ischemia or multiple-organ failure in all 73 patients.

	Discussion

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Selective perfusion of renal and intestinal arteries by means of left-heart bypass and selective perfusion catheters is feasible and safe. The technique is simple and not time-consuming. When only volume flow was assessed, renal insufficiency and finally renal failure were relatively low but did not compare favorable with other series [4] [7]. However, when perfusion pressure measurements were added and mean pressures were adjusted to higher levels in order to maintain urine output, renal failure could be avoided in all patients. This experience cannot be scientifically proven because of the lack of statistical significance. However, from a clinical point of view, we believe that this additional improvement is mandatory to perfuse the kidneys adequately since the kidneys are more pressure-dependent than flow-dependent. This might explain the results of Safi et al. [4], who even found visceral perfusion a risk factor for renal failure. They did not measure arterial pressures in the perfusion system. Since we intentionally had to increase the mean pressures in most patients, we underline the importance of doing so. The main advantage of selective perfusion is obtained in patients with preoperatively impaired renal function, which in fact is the major risk factor for the development of renal failure [3] [7] [8]. In the present series, 95% of the patients treated with pressure-controlled perfusion had stable creatinine levels, including ten of the 12 patients with pre-existing renal damage and creatinine levels higher than 200 mmol/l. Creatinine levels increased to 450 mmol/l in only two patients (5%), who had to undergo peritoneal dialysis for 2 days, whereafter they stabilized. In these two patients, we were unable to reach acceptable arterial pressures in order to maintain urine output, which immediately indicates the drawback of the perfusion system. The diameter of the catheters and the multiple connections jeopardize the rheological properties of the blood, and excessive pressures in the centrifugal pump have to be created to ensure adequate pressures at the tips of the catheters. Larger-diameter perfusion catheters without connections are currently constructed to overcome these problems.

The main question in the literature is whether retrograde aortic and selective organ perfusion is necessary. Cambria et al. [9] reviewed the larger series recently published, showing an overall renal failure rate of 14% when using the clamp-and-sew technique, which was comparable to the outcome for the distal bypass perfusion set-up (14.2%). They emphasize operative expediency and simplicity without extracorporeal bypass with specific regional hypothermia. Our goal, however, was to reduce the incidence of renal failure further, because patients who have this complication have a significantly increased postoperative mortality risk [7] [10]. Another advantage of selective perfusion is the available time to perform perfect reconstructions. As shown in the present study, urine output continued, irrespective of cross-clamp time, allowing renal and visceral artery repair with separate grafts, if necessary. In practice, the aorta and its branches are often diseased. When using the clamp-and-sew technique without adjunctive procedures, every selective graft would add ischemic time, thereby increasing the risk of postoperative complications. It is therefore understandable that the series using the clamp-and-sew technique hardly include selective grafts.

In addition to hemodynamic advantages, distal aortic perfusion reduces post-clamp acidosis, the risk of cerebral perfusion overload, and the need for pharmacological intervention during clamping. Extracorporeal circulation, however, might induce complications like arterial dissection, damage to the left atrium or pulmonary vein, embolization and bleeding. We did not encounter these problems.

In conclusion, this clinical study shows that renal and visceral ischemia can be reduced significantly by continuous perfusion during cross-clamping in TAAA repair. It is therefore recommended that this will be included in the protocol for TAAA repair, especially for type-II aneurysms [11]. Not only sufficient volume flow but also adequate arterial pressure appears to be essential for maintaining renal function. It has to be emphasized that scientific proof of this conclusion can only be achieved by performing a prospective randomized trial comparing selective perfusion and no perfusion at all or selective perfusion and other protective measures.

	Footnotes

 
Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, September 28 – October 1, 1997.

	Appendix A. Conference discussion

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Dr C. Alhan (Istanbul, Turkey): To maintain adequate pressure, I think you give more blood through the centrifugal pump system. Isn't that so? So is the proximal pressure lower with that technique, and do you manage for this to raise the pressure? Do you give inotropes or things like that?

Dr Eijsman: Did I understand your question correctly, that you're asking if we systemically use inotropic drugs.

Dr Alhan: Yes, systemically, to maintain proximal pressure. Because when your volume going into the visceral vessels gets higher, then I believe you'll have hypotension proximally in the cerebral length.

Dr Eijsman: In some cases pharmacological management is necessary to maintain adequate perfusion pressure.

Dr R. Dion (Brussels, Belgium): As you may know, we use the somato-sensory-evoked potentials for monitoring the spinal cord because our neurophysiologists are not convinced that motor-evoked potentials bring any definite advantage from the physiological point of view. In addition, they are not always reliably recordable in an anesthetized and curarized patient, and may need a very high intensity stimulus, which might be harmful for the brain. So my first question is: are you successful in recording the motor-evoked potentials in every patient?

The second question is: if you want to follow the motor- or the somatosensory-evoked potentials, you have to continuously perfuse the spinal cord in order to maintain its function. Therefore, while the aortic aneurysmal segment is excluded from blood perfusion after application of both clamps, you should find the way to selectively perfuse the intercostal and lumbar tributaries that are comprised between the clamps. How do you manage that?

Dr Eijsman: The first answer is yes, we are very enthusiastic about motor-evoked potentials. But we are just humble surgeons. There is a neurophysiologist standing in the OR together with a very experienced anesthetist. And yes again, it's possible in all patients to do motor-evoked potentials. It's a special technique. Since time was limited I couldn't show it here, but I can show you slides where at the moment of clamping motor-evoked potentials were lost and we then realized that we had just cut out a very essential artery. In that artery we did selective perfusion, which we generally do not. And then we very quickly reanastomosed that artery in the prosthesis because that artery turns out to be essential. The moment we did reperfusion of this artery, the motor-evoked potentials came back.

Dr D. Dougenis (Patras, Greece): Since you're performing the anastomosis, the upper anastomosis, with the clamp on, I would like to ask you what was your complication rate in terms of embolic episodes, neurological deficits from the brain, since there have been some data stating that the clamp, in particular for aneurysms of Type II, originating near the left subclavian orifice, may cause embolic episodes? And also have you ever used hypothermia for prevention of spinal cord and visceral ischemic injury?

Dr Eijsman: To answer your last question first, no, we did not use hypothermia, but you should be aware that those are thoracoabdominal aneurysms. The arch is not involved in this series. And we were probably lucky, just like you, we didn't see cerebral emboli in this series.

	References

Top Abstract Introduction Patients and methods Results Discussion Appendix A. Conference... References

 

1. Svensson L.G., Coselli J.S., Safi H.J., Hess K.R., Crawford E.S. Appraisal of adjuncts to prevent acute renal failure after surgery on the thoracic or thoracoabdominal aorta. J Vasc Surg 1989;10:230-239.[Medline]
2. Safi H.J., Cox G.S. A new technique for left renal cryopreservation. J Am Coll Surg 1994;178:629-631.[Medline]
3. Crawford E.S., Crawford J.L., Safi H.J., Coselli J.S., Hess K.R., Brooks B., Norton H.J., Glaeser D.H. Thoracoabdominal aortic aneurysms: preoperative and intraoperative factors determining immediate and long-term results of operations in 605 patients. J Vasc Surg 1986;3:389-404.[Medline]
4. Safi H.J., Harlin S.A., Miller L.L., Iliopoulos D.C., Joshi A., Tabor M., Zippel R., Letson G.V. Predictive factors for acute renal failure in thoracic and thoracoabdominal aortic aneurysm surgery. J Vasc Surg 1996;24:338-345.[Medline]
5. Jacobs M.J.H.M., de Mol B.A.J.M., Legemate D.A., Veldman D.J., de Haan P., Kalkman C.J. Retrograde aortic and selective organ perfusion during thoracoabdominal aortic aneurysm repair. Eur J Vasc Endovasc Surg 1997;14:360-366.[Medline]
6. de Haan P., Kalkman C.J., de Mol B.A., Ubags L.H., Veldman D.J., Jacobs M.J.H.M. Efficacy of transcranial motor-evoked myogenic potentials to detect spinal cord ischemia during operations for thoracoabdominal aneurysms. J Thorac Cardiovasc Surg 1997;113:87-101.[Abstract/Free Full Text]
7. Kashyap, V.S., Cambria, R.P., Davidson, J.K., l'Italien, G.J. Renal failure after thoracoabdominal aortic surgery. J Vasc Surg 1998, in press.
8. Schepens M., Defauw J., Hamerlijnck R., Vermeulen F. Risk assessment of acute renal failure after thoracoabdominal aortic aneurysm surgery. Ann Surg 1994;219:400-407.[Medline]
9. Cambria, R.P., Davidson, J.K., Zanetti, S., l'Italien, G.J., Atamien, S. Thoracoabdominal aneurysm repair. Perspectives over a decade with the clamp and sew technique. Ann Surg, 1998, in press.
10. Gilling-Smith G.L., Worswick L., Knight P.F., Wolfe J.H.N., Mansfield A.O. Surgical repair of thoracoabdominal aortic aneurysm: 10 years experience. Br J Surg 1995;82:624-629.[Medline]
11. Jacobs MJHM, Myhre HO, Norgren L for the Second Nordic Workshop Group. Thoracoabdominal aortic surgery with special reference to spinal cord protection and perfusion techniques. Eur J Vasc Endovasc Surg, 1998, in press.

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