**4. Conclusion**

222 Front Lines of Thoracic Surgery

Bachet's initial description of arch reconstructions using "cold cerebroplegia" at 6-12C in 1991 was also remarkable for the fact that he performed all of his arch reconstructions under moderate hypothermic circulatory arrest at core temperatures between 25-28°C (36). Using this technique he reported excellent neurologic outcomes with an incidence of PND and TND of 2.1% and 4.3% respectively. Minatoya and colleagues evaluated outcomes of 229 patients who received arch reconstruction with HCA+bSACP at three different temperatures: 20C (n=81), 25C (n=81), and 28C (n=67). 81% of all patients received total arch replacement. There were no significant differences between the three groups with regards to the incidence of mortality, PND or TND (54). The use of MHCA+ACP for arch reconstruction has also been reported by several groups in the setting of acute Type A aortic

At Emory, MHCA+uSACP is our preferred method of cerebral protection. All circulatory arrest cases are performed by cannulating an 8mm Dacron graft sewn to the right axillary artery. This is based upon a strong belief that axillary artery cannulation reduces the incidence of PND. This is supported by the important analysis by Svensson and colleagues who reviewed their stroke rates in 1336 circulatory arrest cases with different sites for arterial cannulation (ascending aorta, femoral, axillary, and innominate). They determined that cannulating a graft sewn to the right axillary artery resulted in the lowest incidence of PND (14). Although the mechanism of the protective effect of axillary cannulation is unknown, we have two hypotheses. The first is that axillary artery cannulation provides retrograde blood flow down the innominate artery, which may prevent atheroembolic disease from the ascending aorta. The second hypothesis relates to the differences in technique between uSACP and bSACP. In bSACP, there is a risk of cannulation-induced embolic injury from the introduction of cerebral perfusion catheters into the innominate and left common carotid arteries, especially in patients with atheromatous aortic arch disease. With uSACP, the innominate artery is occluded at the time of circulatory arrest and antegrade blood at 16°C is perfused at 10ml/kg/min through the right common carotid artery, right vertebral artery as well as through the left carotid system via intracranial and extracranial collaterals (58). This avoids manipulation of the ostia of the great vessels which

In our initial report using this technique, we reviewed 412 arch reconstruction cases (elective and emergent) performed under MHCA with uSACP at core temperature of 25.7°C at the initiation of circulatory arrest. Operative mortality was 7.0%, and the incidence of PND and TND were 3.6% and 5.1% respectively with no cases of paraplegia. There were four (1%) deaths due to mesenteric inschemia, and three of these four patients presented with an acute Type A aortic dissection with preoperative visceral malperfusion. There was a 4.6% incidence of renal failure requiring dialysis. In a multivariate analysis, moderate hypothermia was not found to be an independent risk factor for mortality, PND, TND or renal failure requiring dialysis (55). Since that initial report, our experience has grown and we have continued to perform arch reconstructions at more moderate levels of hypothermia. In our recent study, we compared the outcomes of 257 patients undergoing arch reconstruction at 24.3°C to 265 patients undergoing arch reconstruction using at 28.5 °C. Both groups had adjunctive uSACP. There was no difference in mortality, TND or renal failure requiring dialysis between the two groups. The Stroke rate, cardiopulmonary bypass, cross clamp, post op ventilator times and ICU and hospital lengths of stay were all reduced in the 28.5C group (Table 2) (59). We feel that these results add to the growing body of literature which supports the strategy of moderate hypothermic circulatory arrest + uSACP as a highly effective cerebral protection strategy for aortic arch replacement (36, 54, 55, 56).

dissection with results equivalent to those achieved with DHCA (55, 56, 57).

are often covered with large, friable atherosclerotic plaques.

Overall outcomes of patients undergoing aortic arch surgery have significantly improved over the past 3 decades. Advancements in surgical technique, prosthetic grafts and most importantly cerebral protection strategies have all contributed to better results. Despite the evidence presented in the preceding paragraphs, the optimal method of cerebral protection for arch reconstruction remains a controversial topic. All of these data are observational or retrospective studies. Due to surgeon bias and the limited number of arch cases performed, it is unlikely that there will ever be a prospective, randomized, controlled trial to determine the "gold standard" method of cerebral protection.

As we have demonstrated, there are many different methods of cerebral protection which range from simple to complex. The arterial cannulation site, level of hypothermia, and the use of adjunctive cerebral perfusion are factors which have been shown to impact neurologic outcomes following arch reconstruction. It is highly likely that most cardiothoracic surgeons do 1-2 arch reconstructions/year (usually in the setting of Type A dissection) and are most comfortable using DHCA at 18C with femoral cannulation as their sole method of cerebral protection (Personal communications). The cerebral protection conferred by deep hypothermia is undisputed, and for short circulatory arrest times (<30 minutes) the addition of RCP or ACP may not significantly impact neurologic outcomes. However it is generally agreed upon that for prolonged circulatory arrest times (>45) minutes, adjunctive ACP or RCP should be utilized. When using MHCA, ACP must be employed as it is the only adjunctive method reported with more moderate levels of hypothermia. Animal studies have demonstrated equivalent bilateral perfusion with the use of uSACP or bSACP, and clinical data has reported excellent neurologic outcomes with either method (43, 54, 55, 57). Surgeons should be familiar with the technical aspects of all

Cerbral Protection Strategies for Aortic Arch Surgery 225

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**13** 

et al.,

*1,2Germany 3United Kingdom* 

**Recent Advances in the** 

Laszlo Göbölös1,3<sup>∗</sup>

*University Hospital Regensburg,* 

 *Southampton University Hospital Trust,* 

**Management of Acute Aortic Syndrome** 

*1Department of Cardiothoracic Surgery, University Hospital Regensburg,* 

Type A acute aortic dissection is one of the most serious cardiovascular conditions and is associated with significant morbidity and mortality. A half century ago, Hirst et al published a milestone article describing the linearized mortality rate of one percent per hour after the onset of an ascending aortic dissection [1]. Hence, the importance of accurate, quick and reliable diagnosis, as the timing of procedure is vital for optimal management of this highly lethal condition. Despite improvements in the diagnostic modalities, surgical techniques and perioperative care, the overall mortality remains high, between 10% and

Due to its major role in systemic perfusion, the aorta and its main branches after dissection are often challenging when trying to prevent surgical morbidity and mortality. The complexity of aortic dissection presents not only a pure cardiovascular surgical task, but also consideration must be given to protection of the myocardium, cerebrum, peripheral tissues and organs. An early fatal result of aortic dissection is due to ischaemic injury to the brain or heart, although longer peripheral ischaemia can cause multiorgan failure resulting in extended hospital stay, increased morbidity and mortality. Alexis Carrel highlighted the risks of surgery in 1910 with the following short summary on aortic interventions: "The main danger of the aortic operation does not come from the heart or from the aorta itself, but from the central nervous system." Even a century later, we are still trying to optimize cerebral protection, despite having significantly wider range of diagnostic and therapeutic

Advances in our understanding of varying pathologies of aortic dissections have improved as have the technological developments in the modes of detection. These advances together

Maik Foltan1, Peter Ugocsai2, Andrea Thrum1, Alois Philipp1, Steven A. Livesey3, Geoffrey M. Tsang3

with improved therapeutic options have raised expectations for better outcomes.

**1. Introduction** 

30% [2].

modalities.

and Sunil K. Ohri3

*3Department Cardiothoracic Surgery, Southampton General Hospital,* 

*2Institute for Clinical Chemistry and Laboratory Medicine,* 

[59] Leshnower BG, Thourani VH, Myung RJ, et al. Aortic Arch Reconstruction at 28°C: A Comparative Analysis of Outcomes using Mild vs Moderate Hypothermia. *Ann Thorac Surg* Submitted.
