Interactive Cardiovascular and Thoracic Surgery 2:40-42(2003)
© 2003 European Association of Cardio-Thoracic Surgery
New ideas - Vascular thoracic |
Outflow switch technique during the left heart bypass to prevent the distal embolization in the distal aortic arch surgery
Shiro Sasaguri*,
Hideaki Nishimori,
Atsushi Hata and
Takeshi Fukutomi
Department of Surgery II, Kochi Medical School, Okoh, Nankoku city, Kochi 783-8505, Japan
* Corresponding author. Tel.: +81-88-880-2373; fax: +81-88-880-2376
sasaguri{at}kochi-ms.ac.jp
Received May 12, 2002;
received in revised form October 22, 2002;
accepted November 4, 2002
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Abstract
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Aortic cross-clamping has the risk of inducing the postoperative embolization including the stroke during the repair of distal aortic arch with the use of left heart bypass. In this paper, we present a modified technique to reduce the embolization by switching the outflow of the left heart bypass from left atrium to the side branch of the inserted graft.
Key Words: Cerebral protection; Extracorporeal circulation; Great vessels
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1. Introduction
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Stroke is a devastating complication in surgery of the thoracic aorta, however, it may not be adequately appreciated as a common sequel to descending aortic operations. Recent study by Goldstein et al. demonstrated that the stroke does indeed occur in descending aortic operations as frequently as in ascending aortic operations. They recommended the antiembolic measures, including gentle aortic manipulation, through debridement, transesophageal echocardiography, carbon dioxide flooding of the field and proximal clamp application before initiating femoral perfusion [1].
Here we also emphasize the risk of stroke while releasing the clamp and advocate switching the outflow port of left heart bypass (LHB) from the left atrium (LA) to the branch of the inserted graft which may prevent the detached debris from getting into the cerebral circulation in the surgery of distal aortic arch or proximal descending aorta.
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2. Technique
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The operative technique involved a left antero-axillary thoracotomy for the distal aortic arch aneurysm [2]. LA was cannulated as an outflow site and the femoral artery or distal thoracic aorta as an inflow site. Once the LHB was established, the proximal aorta was cross-clamped either between the left carotid artery and the left subclavian artery or just distal to the left subclavian artery. Perfusion was maintained with a centrifugal pump (Medtronic INTERSEPT CB6500; Minneapolis, MN, USA) to keep the mean distal aortic pressure over 70mmHg. Blood filter (Medtronic AFFINITY CB351) was incorporated in the inflow line. The proximal aorta was transected and the graft with a side branch was anastomosed. After completing the proximal anastomosis, the blood drainage was switched from LA to the side branch at the same time of declamping. (Fig. 1). This procedure thus prevents the tiny debris from getting into the turbulent flow near the re-instituted clamp by sucking into the side branch. Fig. 2 shows the macroscopic picture of the blood filter and the electron micrographic picture of the tiny debris, which was trapped by the mesh of the blood filter. These debris which otherwise might have flowed into the cerebral circulation have been demonstrated in the recent three out of five cases, in which the filters had been examined under the electron microscope following the distal aortic arch replacement under LHB.
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Fig. 1 Outflow switch during left heart bypass. (A) Standard left heart bypass with left atrial drainage turbulent flow near the clamp may induce the cerebral embolism from the clamp site. (B) Outflow switch after completion of proximal anastomosis from the left atrium to the side branch of the graft. The debris may be flushed out through the outflow. LA, left atrium; arrow, blood stream; round spot, clamp site; *, debris.
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Fig. 2 (A) Macroscopic picture showing a large particle trapped by the blood filter. (B) Electron micrographic picture of a blood filter showing the tiny debris, which has been trapped by the mesh.
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3. Discussion
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The repair of the distal aortic arch in patients with degenerative aneurysms and superimposed atherosclerosis can be a particularly hazardous procedure. The options for repairing these aneurysms are: (1) LHB with clamping the aorta between the left carotid artery and left subclavian artery through the left lateral thoracotomy and; (2) deep hypothermic circulatory arrest (DHCA) with or without retrograde cerebral perfusion (RCP) either through a left lateral thoracotomy or median sternotomy. DHCA has several advantages such as no usage of cross-clamping, technical simplicity and bloodless operative field, however DHCA itself does not flush back the tiny debris from the cerebral tributaries, even with the concomitant use of RCP. LHB which maintains the cerebral blood flow during the procedure, can avoid the cerebral global ischemia and also prevents the coagulopathy by the profound hypothermia, thus reducing the morbidity especially in the high-risk patients. However, the reported risk of the postoperative stroke in cross-clamping technique is ranging from 3 to 14%, which is higher than that in DHCA [3–5]. Several techniques have been demonstrated to reduce the embolization [5]. Among them, external flushing is the most commonly used method, which flushes the aorta through the graft after completing the proximal anastomosis. However, re-occlusion of the graft for the distal anastomosis may induce the turbulence near the clamp, which may disrupt the debris from the injured aortic wall, thus resulting in the embolization. Internal flushing is another method to prevent the embolization. In this method, the proximal clamp is released only after the graft is in place, thus flushing the debris distally. This technique, however, has a risk of producing the distal embolization and is sometimes difficult in controlling bleeding from the proximal anastomosis through the limited operative field.
Outflow switch technique, which has been demonstrated here is a method to prevent the turbulent flow near the re-instituted clamp by draining the blood through the side branch of the graft that is placed just proximal to the clamp, thus, evacuating the debris which may be detached from the injured aortic wall following clamping. This method is simple and may increase the benefits of LHB by reducing the incidence of embolization.
doi:10.1016/S1569-9293(02)00097-X
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References
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- Goldstein LJ, Davies RR, Rizzo JA, Davila JJ, Cooperberg MR, Shaw RK, Kopf GS, Elefteriades JA. Stroke in surgery of the thoracic aorta: incidence, impact, etiology, and prevention. J Thorac Cardiovasc Surg. 2001;122:935–945[Abstract/Free Full Text]
- Sasaguri S, Yamamoto S, Fukuda T, Hosoda Y. Anteroaxillary thoracotomy facilitates the use of retrograde cerebral perfusion in distal aortic arch reconstruction. Ann Thorac Surg. 1996;62:1861–1862[Abstract/Free Full Text]
- Svensson LG, Crawford ES, Hess KR, Coselli JS, Safi HJ. Experience with 1509 patients undergoing thoracoabdominal aortic operations. J Vasc Surg. 1993;17:357–370[CrossRef][Medline]
- Crawford ES, Svensson LG, Coselli JS, Safi HJ, Hess KR. Surgical treatment of aneurysm and /or dissection of the ascending aorta, transverse aortic arch. Factors influencing survival in 717 patients. J Thorac Cardiovasc Surg. 1989;98:659–674[Abstract]
- Kieffer E, Koskas F, Walden R, Godet G, Le Blevec D, Bahnini A, Bertrand M, Fleron MH. Hypothermic circulatory arrest for thoracic aneurysmectomy through left-sided thoracotomy. J Vasc Surg. 1994;19:457–464[Medline]
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Abstract
1. Introduction