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Ann Thorac Surg 1995;60:76-77
© 1995 The Society of Thoracic Surgeons
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Introduction |
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 Top Introduction |
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DR JOSEPH S. COSELLI (Houston, TX): Once again, Dr Kouchoukos' presentations and publications remain an ideal we all strive to achieve.
I thank Dr Kouchoukos for the opportunity to review the manuscript before the meeting. Doctor Kouchoukos and associates report on an experience with truly excellent results in a selective cohort of patients treated with an evolving strategy over a 9-year period. In this group of patients, however, I believe we need to make two clear distinctions, which Dr Kouchoukos has already pointed out.
One is the use of deep hypothermia and circulatory arrest in the left chest for aneurysms where, for technical or anatomic reasons, it is simply not possible to place a clamp for proximal control. These would include large aneurysms of the proximal descending thoracic aorta where no appropriate neck for proximal clamping is anatomically available.
The second is the extension of this modality for the purpose of spinal cord and visceral protection, particularly renal, in patients in whom cross-clamping proximally is possible. In my experience, it has been used relatively infrequently, for a total of 28 patients in whom circulatory arrest was used through the left chest out of 717 patients with either descending thoracic or thoracoabdominal aortic aneurysms. In these 28 patients, the development of paraplegia or a paraparesis was 7.14% and the early mortality was 3 patients (10.7%), comparing favorably with other techniques such as atriofemoral bypass or simple cross-clamping. In 107 patients treated with atriofemoral bypass, the overall neurologic deficit rate, including paraplegia and paraparesis was 3.74% and mortality was 4.67%; for simple cross-clamping the rates were 5.42% and 4.55%, respectively. Although the mortality is increased numerically over the latter two techniques, no statistical difference regarding the incidence of neurologic deficits has been identified.
A problem still remains regarding the postoperative development of neurologic deficits in the Crawford type II patients (thoracoabdominal aortic aneurysms). In 137 Crawford type II patients out of 498 consecutive patients in a personal series, the mortality was 5.8% and the paraplegia and paraparesis rate combined was 10.9%. It makes me wonder whether in Kouchoukos and associates' series we are not trading off a certain amount of mortality for a decrease in the incidence of neurologic deficits.
Doctor Kouchoukos, why did you use patients from other institutions for comparison with your own data, rather than using patients from your own institution? Additionally, were the 51 patients in your series consecutive; if not, how many other operations in patients with descending and thoracoabdominal aneurysms were carried out during the same time period of the study? The results in those patients, I think, would be informative.
DR ALLAN WOLPOWITZ (Hollywood, FL): I have two technical questions. If you have to reperfuse the descending thoracic aorta at the same time that you are perfusing the femoral, the two perfused systems require different techniques, necessitating two oxygenators and two arterial heads. Is this a standard set-up?
With all patients with elevated creatinine levels we routinely use continuous arteriovenous hemofiltration, but it appears as if we dialyze aprotinin out. This might be the reason that there is disseminated intravascular coagulation postoperatively despite use of aprotinin.
DR TIRONE E. DAVID (Toronto, Ont, Canada): I enjoyed your presentation very much, Dr Kouchoukos. I have been very reluctant to place patients on cardiopulmonary bypass through femoral cannulation if they have extensive atherosclerotic aneurysm because of the possibility of embolization to the brain once the flow in the thoracic and abdominal aorta is reversed. Would you care to comment about that?
DR KOUCHOUKOS: Doctor Coselli, the issue of trading a potentially higher early mortality rate for a lower incidence of spinal cord ischemic injury is a very important one. We made the decision to use hypothermic cardiopulmonary bypass and circulatory arrest in patients in whom the risk of spinal cord ischemic injury was judged to be approximately 10% or greater, and this included patients with aneurysms involving most or all of the descending thoracic aorta and patients with Crawford type I, II, and III thoracoabdominal aneurysms. The 30-day mortality rate for the 43 patients in these categories was 11.6%, and the rate of paraplegia or paraparesis was 7%. During the study interval, alternative operative techniques were not used for patients in these categories. For patients with aneurysms confined to the upper or the mid-descending thoracic aorta we used distal perfusion with femoral vein to femoral artery bypass, and for patients with Crawford type IV thoracoabdominal aneurysms we used simple aortic clamping.
Doctor Wolpowitz, we used separate pump-oxygenator systems to perfuse the upper and lower parts of the body. Separate systems are necessary to regulate blood flow precisely to these two areas. We did not routinely use a hemoconcentrator, and thus I cannot comment on whether or not aprotinin was removed from the circulation.
Doctor David, I share your concern about the potential for embolization of atheromatous material to the brain if femoral artery perfusion is used in patients with arteriosclerotic aneurysms. The 2 patients in our series in whom embolic strokes developed had atherosclerotic disease in the aorta proximal to the aneurysm and had clamps placed on this segment. We believe this is a more likely cause for embolic stroke and we no longer place clamps on the proximal aorta. Since we abandoned this maneuver we have seen no embolic strokes.
The optimal level of hypothermia that will provide maximal protection of the spinal cord and kidneys is undetermined, and it is possible that a lesser degree of hypothermia may be equally protective and will be associated with less mortality and morbidity than the technique we have reported. However, hypothermia and circulatory arrest will be required for aortic disease that necessitates resection of the aortic arch. Techniques involving the use of distal perfusion with normothermia or mild hypothermia, which have been used by Dr Coselli and others, also have been associated with a lower incidence of spinal cord ischemia injury than the simple aortic clamping technique. However, these perfusion techniques require the use of sequential aortic clamping to minimize the duration of spinal cord ischemia, and this will not be possible in all cases. Thus, in situations where aortic clamping is not possible, use of hypothermic circulatory arrest should be considered.
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