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We are not proponents of profound hypothermia and circulatory arrest for single-stage arch and descending thoracic aortic replacement. As we stated in the introduction to our article, ¹ our use of the technique is highly selective and reserved for instances in which aortic cross clamping may be hazardous because of rupture, excessive aortic size, or atheromatous plaque or debris. In our experience of more than 400 thoracoabdominal aortic aneurysm cases, the combined adjuncts of cerebrospinal fluid drainage, distal aortic perfusion, and active visceral cooling have done a good job in lowering the incidence of neurologic complications and death.² In type I thoracoabdominal and descending thoracic aortic aneurysms, we have had no instances of paraplegia or paraphrases since we began to use these methods.³

There are times, however, when cross clamping is not feasible, and we have no choice but to resort to profound hypothermic circulatory arrest. As for our perfusion techniques, we find no evidence to support Mr Westaby's suggestion that retrograde perfusion produces a higher incidence of stroke than antegrade perfusion. We do not cannulate the ascending aorta or arch as advocated by Mr Westaby for precisely the same reason we do not clamp in this region (ie, the potential for dislodging plaque or debris to the brain).⁴ Mr Westaby comments that with profound hypothermic circulatory arrest, reperfusion to the coronary and brachiocephalic vessels can be accomplished early after the proximal anastomosis. But this technique is not without its problems if a major purpose of cooling the spinal cord is to reduce cord metabolic rate and therefore protect against ischemic injury. Because restoration of circulation to the head would warm the cerebrospinal fluid and the spinal cord, it would remove any protective hypothermic effects to the spinal cord while the distal work was still underway. Our experimental data showed that cerebrospinal fluid temperature correlates with nasopharyngeal temperature but not with core temperature.

The cases we reported here were patients who presented with a high degree of preoperative risk, not unlike many of our other patients. The difference, however, was the noticeably poor outcome. Although small in number, we believed this group deserved notice. We reported only what we encountered, motivated by results that we believe were ominous.

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1. Safi HJ, Miller CC, Subramaniam MH, Campbell MP, Iliopoulos DC, O'Donnell JJ, et al.  Thoracic and thoracoabdominal aortic aneurysm repair using cardiopulmonary bypass, profound hypothermia, and circulatory arrest via left side of the chest incision. J Vasc Surg. 1998;28:591–598
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2. Safi HJ, Campbell MP, Miller CC, Iliopoulos DC, Khoynezhad A, Letsou GV, et al.  Cerebral spinal fluid drainage and distal aortic perfusion decrease the incidence of neurological deficit: the results of 343 descending and thoracoabdominal aortic aneurysm repair. Eur J Vasc Surg. 1997;14:118–124
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3. Safi HJ, Subramanian MH, Miller CC, Coogan SM, Flionlos DC, Winnerkvist A, et al. Progress in the management of type I thoracoabominal and descending thoracic aortic aneurysms. Ann Vasc Surg. In press.
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4. Safi HJ, Miller CC, Azizzadeh A, Campbell MP, Iliopoulos DC, LeBlevec D, et al.  Brain manifestations associated with atherosclerotic aortic arch disease. New trends and developments in carotid artery disease. In:  Branchereau A,  Jacobs M editor. Armonk, NY: European Vascular Course Futura Publishing Company; 1998;p. 117–131
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