Does straight deep hypothermic circulatory arrest suffice for brain preservation in aortic surgery?

Myocardial protection in cardiac surgery-hindsight from the 2020s

Myocardial protection and specifically cardioplegia have been extensively investigated in the beginnings of cardiac surgery. After cardiopulmonary bypass had become routine, more and more cardiac operations were possible, requiring reliable and reproducible protection for times of blood flow interruptions to the most energy-demanding organ of the body. The concepts of hypothermia and cardioplegia evolved as tools to extend cardiac ischaemia tolerance to a degree considered safe for the required operation. A plethora of different solutions and delivery techniques were developed achieving remarkable outcomes with cross-clamp times of up to 120 min and more. With the beginning of the new millennium, interest in myocardial protection research declined and, as a consequence, conventional cardiac surgery is currently performed using myocardial protection strategies that have not changed in decades. However, the context, in which cardiac surgery is currently performed, has changed during this time. Patients are now older and suffer from more comorbidities and, thus, other organs move more and more into the centre of risk assessment. Yet, systemic effects of cardioplegic solutions have never been in the focus of attention. They say hindsight is always 20-20. We therefore review the biochemical principles of ischaemia, reperfusion and cardioplegic extension of ischaemia tolerance and address the concepts of myocardial protection with 'hindsight from the 2020s'. In light of rising patient risk profiles, minimizing surgical trauma and improving perioperative morbidity management becomes key today. For cardioplegia, this means accounting not only for cardiac, but also for systemic effects of cardioplegic solutions.

Therapeutic hypothermia applicable to cardiac surgery

OBJECTIVE

To review the beneficial and adverse effects of therapeutic hypothermia (TH) applicable to cardiac surgery with cardiopulmonary bypass (CPB) in the contexts of various temperature levels and techniques for achieving TH.

DATABASES USED

Multiple electronic literature searches were performed using PubMed and Google for articles published from June 2012 to December 2014. Relevant terms (e.g. 'hypothermia', 'cardiopulmonary bypass', 'cardiac surgery', 'neuroprotection') were used to search for original articles, letters and reviews without species limitation. Reviews were included despite potential publication bias. References from the studies identified were also searched to find other potentially relevant citations. Abstracts, case reports, conference presentations, editorials and expert opinions were excluded.

CONCLUSIONS

Therapeutic hypothermia is an essential measure of neuroprotection during cardiac surgery that may be achieved most effectively by intravascular cooling using hypothermic CPB. For most cardiac surgical procedures, mild to modest (32-36 °C) TH will be sufficient to assure neuroprotection and will avoid most of the adverse effects of hypothermia that occur at lower body core temperatures.

Sun's procedure for complex aortic arch repair: total arch replacement using a tetrafurcate graft with stented elephant trunk implantation

The Sun's procedure is a surgical technique proposed by Dr. Li-Zhong Sun in 2002 that integrates total aortic arch replacement using a tetrafurcated graft with implantation of a specially designed frozen elephant trunk (Cronus(®)) in the descending aorta. It is used as a treatment option for extensive aortic dissections or aneurysms involving the ascending aorta, aortic arch and the descending aorta. The technical essentials of Sun's procedure include implantation of the special open stented graft into the descending aorta, total arch replacement with a 4-branched vascular graft, right axillary artery cannulation, selective antegrade cerebral perfusion for brain protection, moderate hypothermic circulatory arrest at 25 °C, a special anastomotic sequence for aortic reconstruction (i.e., proximal descending aorta → left carotid artery → ascending aorta → left subclavian artery → innominate artery), and early rewarming and reperfusion after distal anastomosis to minimize cerebral and cardiac ischemia. The core advantage of Sun's procedure lies in the use of a unique stented graft, which has superior technical simplicity, flexibility, inherent mechanical durability and an extra centimeter of attached regular vascular graft at both ends. Since its introduction in 2003, the Sun's procedure has produced satisfactory early and long-term results in over 8,000 patients in China and more than 200 patients in South American countries. In a series of 1,092 patients, the authors have achieved an in-hospital mortality rate of 6.27% (7.98% in emergent or urgent vs. 3.98% in elective cases). Given the accumulating clinical experience and the consequent, continual evolution of surgical indications, the Sun's procedure is becoming increasingly applied/used worldwide as an innovative and imaginative enhancement of surgical options for the dissected (or aneurysmal) ascending aorta, aortic arch and proximal descending aorta, and may become the next standard treatment for type A aortic dissections requiring repair of the aortic arch.

Deep hypothermic circulatory arrest

Effective cerebral protection remains the principle concern during aortic arch surgery. Hypothermic circulatory arrest (HCA) is entrenched as the primary neuroprotection mechanism since the 70s, as it slows injury-inducing pathways by limiting cerebral metabolism. However, increases in HCA duration has been associated with poorer neurological outcomes, necessitating the adjunctive use of antegrade (ACP) and retrograde cerebral perfusion (RCP). ACP has superseded RCP as the preferred perfusion strategy as it most closely mimic physiological perfusion, although there exists uncertainty regarding several technical details, such as unilateral versus bilateral perfusion, flow rate and temperature, perfusion site, undue trauma to head vessels, and risks of embolization. Nevertheless, we believe that the convenience, simplicity and effectiveness of straight DHCA justifies its use in the majority of elective and emergency cases. The following perspective offers a historical and clinical comparison of the DHCA with other techniques of cerebral protection.

Midterm experience with modified Cabrol procedure: safe and durable for complex aortic root replacement

OBJECTIVE

To evaluate the early and late outcomes of the modified Cabrol technique as a method of coronary reimplantation during complex composite graft replacement of the ascending aorta.

METHODS

Between 1995 and 2012, 348 patients (mean age, 56 ± 14 years; 283 males and 65 females) underwent composite graft replacement of the ascending aorta, 40 of whom (mean age, 60 ± 12 years; 35 males and 5 females) had one or both coronary ostia reimplanted using a modified Cabrol technique with an 8- to 10-mm Dacron interposition graft. The mean clinical and radiologic (computed tomographic scan) postoperative follow-up was 39 months (range, 1-171 months), via our aortic database, patient interviews, and Social Security Death Index.

RESULTS

Cabrol reimplantation was necessitated by reoperations with anatomically fixed coronary ostia (n = 16, 40%), severely displaced coronary arteries (n = 15, 37.5%), button calcification (n = 4, 10%), coronary anomalies (n = 3, 7.5%), and coronary aneurysm (n = 2, 5%). Of the operations, 20% (8 patients) were urgent interventions. Early mortality was 3 (7.5%) of 40, none related to the Dacron interposition graft. Total late mortality was 16.2%, also not related to the coronary graft. Actuarial survivals were 0.88 ± 0.05, 0.79 ± 0.07, and 0.73 ± 0.08 at 1, 3, and 6 years, respectively. Radiologic follow-up was available for 31 (83.8%) of the surviving patients and revealed that the interposition graft was widely patent in all.

CONCLUSIONS

The modified Cabrol technique using a Dacron interposition graft showed good survival rates and excellent durability over time, confirmed radiographically. These data confirm that it is appropriate to use the Cabrol technique when technical complexity prevents bringing coronary buttons to the main aortic graft.