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Ann Thorac Surg 1995;60:352-353
© 1995 The Society of Thoracic Surgeons
DR SAFUH ATTAR (Baltimore, MD): I congratulate Dr Bavaria and his associates on their solution to this very complicated problem. In our experience, cerebral perfusion, whether antegrade or retrograde, is indicated only when the transverse arch is involved by aneurysmal dissection. There is no need for cerebral perfusion in ascending aortic aneurysms, whether it is dissecting or not.
As far as the descending thoracic aortic aneurysms, our results compare with those of Dr Crawford and are about the same as yours. We have had 87 patients undergoing resection of the descending thoracic aortic aneurysms; 61 had acute traumatic aortic ruptures and 26 chronic aortic aneurysms. Among the acute traumatic ruptures, 22 were resected without shunt with a cross-clamp time of 41 minutes; 31 patients were shunted with a cross-clamp time of 74 minutes. In the chronic aneurysms, 13 had adjunctive support with a cross-clamp time of 22 minutes (these include thoracic and thoracoabdominal aortic aneurysms), and 13 patients had shunt and bypass with a cross-clamp time of 45 minutes. The paraplegia without shunt occurred in 4 of 22 with traumatic aortic rupture, an incidence of 17%, with the shunt it occurred in 6 of 39, which is 15%; in other words, no difference. In patients with chronic aortic aneurysms it occurred in 1 of 13, that is 7%, with or without shunt; the rates were equal. The incidence of renal failure was 5 of 39, that is 12%, in the shunted acute ruptures and 0% in the nonshunted group. In patients with chronic aortic aneurysms, the rate was 1 of 13, again, 7%, without shunt and 15% with the shunt; that is 2 of 13. The survival rate was 72% in acute traumatic aortic ruptures without the shunts and 59% with the shunts. In the chronic descending thoracic aneurysms, we had 11 of 13 survivors (84%) without shunt and 7 of 13 (54%) in the shunted group.
I do not think there is an indication for the use of retrograde cerebral perfusion in ascending aortic aneurysms, and the only reason we currently are using the Bio-Medicus pump with the Carmeda system is for medicolegal reasons. I do not believe any method will prevent the incidence of paraplegia completely, because the etiology is multifactorial.
DR BAVARIA: Regarding Dr Attar's question concerning the indication for retrograde cerebral perfusion in ascending aortic aneurysms, I believe he is fundamentally correct. Retrograde cerebral perfusion is only used during the repair of ascending aortic aneurysms when the fusiform aneurysmal component of the aneurysm extends into the proximal aortic arch. In this particular case, the use of retrograde cerebral perfusion is akin to the indication for retrograde cerebral perfusion in an uncomplicated acute type A aortic dissection. In these cases, the quality of the distal anastomosis is much improved using an ``open anastomotic'' technique. Although the open anastomotic technique for either acute type A dissection or ascending/proximal arch aneurysm only requires between 15 and 30 minutes of retrograde cerebral perfusion, I continue to believe that retrograde cerebral perfusion adds protection even during these short periods of hyperthermic circulatory arrest. I arrive at this conclusion based on an observation we have made regarding postoperative neurologic function in patients undergoing pulmonary thromboendarterectomy. Our standard technique for these patients is to perform the pulmonary thromboendarterectomy during 10- to 12-minute periods of hypothermic circulatory arrest followed by a period of reperfusion. Sometimes it will take between three and five periods of hypothermic circulatory arrest to complete both the left and right endarterectomy. It is my observation that these patients often will have short-term transient nonfocal neurologic damage in spite of the relatively short periods of hypothermic circulatory arrest. For this reason, as well as deairing and embolic reasons, I believe retrograde cerebral protection is appropriate even for relatively short periods of circulatory arrest. An open anastomosis is important in the reconstruction of ascending aortic pathology that extends to the level of the innominate artery because, as Dr Miller of Stanford has said, ``There is nothing quite so terrifying as to take off all your clamps and see your distal anastomosis start coming apart after acute type A dissection.''
In response to Dr Attar's questions regarding traumatic aortic transection, there has been an excellent study by Swenson, after reviewing Crawford's data, showing that when thoracic aortic cross-clamp time exceeded 40 minutes, there was a significant paraplegia rate. Although we usually can repair a thoracic aortic transection faster than 40 minutes, this is not always the case. Additionally, a recent paper by Von Opel revealed that the best circulation management strategy for thoracic aortic transection was distal aortic perfusion without the use of heparin. Our data also support this as we have no paraplegia rate at all in traumatic aortic transection using distal aortic perfusion.
DR HAZIM J. SAFI (Houston, TX): We used hypothermic circulatory arrest and retrograde cerebral perfusion for 29 patients during ascending and arch repair, and no strokes developed. Using conventional methods for 27 patients, stroke developed in 3. We kept the electroencephalogram isoelectric for both groups. With the 29 patients, upon initiation of retrograde cerebral perfusion, the electroencephalogram came back in 2 patients with 1 remaining for a full 55 minutes. Have you had this sort of experience?
DR BAVARIA: As noted, I showed one slide during the talk that was a recording of continuous electroencephalogram during a ``hemi-arch'' aortic reconstruction. As was shown on the slide, we obtained some activity on the electroencephalogram as soon as we started retrograde cerebral perfusion. So I agree with your observation completely.
DR SAFI: Do you also use cerebrospinal fluid drainage for your patients?
DR BAVARIA: I routinely include cerebrospinal fluid drainage for all distal aortic cases that are not emergent. The only time I would not use cerebrospinal fluid drainage is if I decide to go on full cardiopulmonary bypass with 25,000 units of heparin as opposed to just 5,000 units. In those patients I will not use cerebrospinal fluid drainage.
DR SAFI: I would like to make an appeal to the community of vascular surgeons at large: when we report the surgical results of thoracoabdominal aortic aneurysm repair, we should make sure to distinguish the separate aneurysm types and more or less concentrate on the higher risk type I and type II aneurysms, because for type IV and type III, the incidence of paraplegia is less than 5% and you need 500 cases to prove your point.
DR BAVARIA: I completely agree. For the statistical analysis of paraplegia in this article, I removed Crawford type IV thoracoabdominal aneurysms from consideration because there is no place for ``circulation management'' in type IV repairs. However, during the routine reconstruction of Crawford type III thoracoabdominal aneurysms, we do put an aortic cross-clamp directly superior to the celiac artery and perform the proximal anastomosis using distal perfusion and then perform the mesenteric anastomosis in a sequential fashion.
Related Article
Ann. Thorac. Surg. 1995 60: 345-352.
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