Cerebral Protection in Aortic Arch Surgery: Hypothermia Alone Suffices

Cerebral protection has been the cornerstone of successful aortic arch surgery for almost 40 years. Aneurysms of the aortic arch are among the most challenging cases for surgical treatment and require procedural expertise for their safe conduct. Up to now, 3 main strategies for cerebral protection of patients undergoing extensive aortic surgery have been developed and studied. These are straight deep hypothermic circulatory arrest (DHCA), retrograde cerebral perfusion (RCP), and antegrade cerebral perfusion (ACP).1–3 Straight DHCA used to be the preferred technique; however, the recent trend among cardiothoracic surgeons is to avoid straight DHCA in favor of such adjunctive perfusion techniques as RCP or ACP.4 Therefore, the possible superiority of one of these 3 techniques has been an ongoing topic for debate. At our center, straight DHCA has been the method of choice for the absolute majority of complex procedures involving the aortic arch. We believe that straight DHCA is a very appealing method of cerebral protection, because it is quick and simple. There is no need for additional tubes or cannulas, which always carry the risk of intimal injury or embolization when inserted in an antegrade fashion. The operative field stays dry and free of mechanical encumbrances that can compromise exposure of the anastomosis. Furthermore, the surgeon's attention is not distracted by any problems associated with perfusion techniques. For example, flow rate is always difficult to determine and can result in hypoperfusion (if the flow is too slow) or cerebral edema (if the flow is too fast). Then, in ACP, there is still the debate over which vessels (and how many) need to be perfused. This can become a serious issue, especially in patients with aortic dissection. Further, clamping the left subclavian artery in order to prevent steal of perfusate into the open aortic arch might or might not be necessary; this is another matter still in need of clarification. We argue that straight DHCA remains a very effective method of brain protection during aortic surgery, even when used without adjunctive perfusion. The analysis of a 10-year experience in nearly 400 patients has yielded excellent clinical results.5 This study included ascending as well as descending and thoracoabdominal aortic operations in elective and emergent settings. The mortality rate for procedures of the ascending aorta and arch was 2.0% in elective cases, and the stroke rate was only 1.9%.5 We are not aware of better operative survival and stroke rates with the use of ACP or RCP.6 In the few strokes that did occur with DHCA, computed tomographic evaluation revealed that two thirds were embolic (and therefore not protection related); the remaining one third appeared to be hypoperfusion related (and potentially protection related). The mean DHCA time was 31 min (range, 10–66 min). In patients with DHCA times that exceeded 40 minutes, the stroke rate increased significantly to 13.1%, with a similar pattern upon computed tomographic evaluation. Low DHCA times can be achieved if hemiarch replacement is performed, which suffices for many combined procedures of the ascending aorta and arch, as well as for many acute type A dissection repairs. In addition, straight DHCA can accommodate even complex arch reconstructions with elephant trunk or arch vessel replacement—especially if done with an anastomosis between the left carotid and left subclavian arteries, which facilitates exposure, anastomosis, and hemostasis (Fig. 1 4). Fig. 1 Our preferred alternative technique of arch reconstruction with a 2-vessel Carrel patch.4 Reprinted with permission from Elsevier. In a separate study of patients in high-cognitive professions who underwent aortic arch surgery with use of DHCA, we found that these patients manifested very little cognitive change in association with DHCA. Excellent preservation of functional state was found: there was no difference between patients who underwent operation with or without DHCA.7 Currently, the method of brain protection to use in each specific case is largely up to the surgeon's personal preference or to the specific experience of the medical center. Straight DHCA remains an extraordinarily effective method. Instincts, memories, skills, and cognition emerge fully intact after periods of complete brain silence and nonperfusion. Gathering enough data to prove the superiority of one method over another will probably require several more decades. We do not want to argue against ACP, which should be performed in extremely complex cases that are likely to require long intervals before restoration of brain perfusion. The performance of right axillary perfusion has technically facilitated ACP. However, on the basis of our extremely favorable experience, we argue that convenience, effectiveness, simplicity, and noninferiority in comparative studies still render straight DHCA a viable option.