Optimal Cerebral Protection Strategies in Aortic Surgery

Selective cerebral extracorporeal circulation-enhanced total endovascular arch replacement using in situ fenestration

In this article, we present a newly designed cerebral perfusion technique during the in situ fenestration procedure with three covered stent placement in an endovascular total aortic arch repair of a 68-year-old male patient. This technique enables the endovascular repair of the ascending aorta and aortic arch pathologies with commonly available thoracic aorta stent grafts in a safer and more effective manner.

Total Endovascular Aortic Arch Repair: From Dream to Reality

The gold-standard therapy for the treatment of aortic arch pathologies is conventional open surgery. Recently, total endovascular aortic arch replacement with branched stent-grafts has been introduced into clinical practice with the aim of reducing invasiveness especially in selected high-risk patients. The aim of this review is to describe the two most commonly used branched devices for endovascular arch stent-grafting: Nexus (Endospan, Herzlia, Israle) and RelayBranch (Terumo Aortic, Glasgow, United Kingdom). Nexus is a CE-certified off-the-shelf, single branch, double stent graft system. It consists of two different components: a main module for the aortic arch and the descending aorta with a side-branch for the brachiocephalic artery (BCA), and a curved module for the ascending aorta that lands into the sino-tubular junction and connects to the main module through a side-facing self-protecting sleeve. Nexus may be used in urgent-emergency cases and also in patients with only one suitable supra-aortic target vessel but, on the other hand, it makes cerebral blood flow dependent on one source vessel only. The RelayBranch Thoracic Stent-Graft System is a custom made, double branched endograft with a wide window on its superior portion to accommodate two inner tunnels for BCA and left common carotid artery connection; bilateral cervical accesses are generally used to advance guidewires for catheterization of the inner tunnels in a retrograde fashion. RelayBranch can be customized on every patient’s specific anatomy and provides a double blood source for the brain, but it cannot be used in urgent-emergency conditions. Therefore, in order to optimize outcomes, the choice of the most appropriate device should be made considering pros and cons of each system and patient’s anatomy by an experienced aortic team. In conclusion, total endovascular aortic arch exclusion is a promising reality in selected high-risk patients.

Anaesthetic-surgical guide in the treatment of ascending aorta and surgery of the ascending aorta and aortic arch. Consensus document of the Spanish Society of Cardiovascular and Endovascular Surgery and the Sociedad of Anaesthesiology, Resuscitation and Pain Therapy

Aortic pathology is always a challenge for the clinician, and must be diagnosed and treated by a multidisciplinary team due to the technical and technological complexity of the resources used. Ongoing efforts to implement a systematic, protocolized approach involving "Aortic teams" made up of cardiologists, cardiac surgeons, vascular surgeons, anaesthesiologists and radiologists, among others are now leading to improved outcomes. The aim of this consensus document drawn up by the Aortic working groups of the Spanish Society of Anaesthesiology, Resuscitation and Pain Therapy (SEDAR) and the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) is to disseminate a set of working protocols. The latest consensus document of the European Association for Cardio-Thoracic Surgery (EACTS) and the European Society for Vascular Surgery (ESVS) define the concept of "AORTIC TEAM"(1). The aortic team should be closely involved from diagnosis to treatment and finally follow-up, and should be formed of cardiac and vascular surgeons working together with anaesthesiologists, cardiologists, radiologists and geneticists. Treatment of aortic pathologies should be centralised in large centres, because this is the only way to effectively understand the natural course of the disease, provide the entire range of treatment options under one umbrella and treat potential complications. A streamlined emergent care pathway (24/7 availability), adequate transportation and transfer capabilities, as well as rapid activation of the multidisciplinary team must be available. In light of the complexity and constant evolution of therapeutic options, we present this first version of the Anaesthesiology and surgical guidelines for surgery of the ascending aorta and aortic arch. Some questions will no doubt remain unanswered, and future versions will include new techniques that, though implemented in some centres, are still not widely recommended.

Ketamine Mitigates Neurobehavioral Deficits in a Canine Model of Hypothermic Circulatory Arrest

Hypothermic circulatory arrest is a protective technique used when complete cessation of circulation is required during cardiac surgery. Prior efforts to decrease neurologic injury with the NMDA receptor antagonist MK801 were limited by unacceptable side effects. We hypothesized that ketamine would provide neuroprotection without dose-limiting side effects. Canines were peripherally cannulated for cardiopulmonary bypass, cooled to 18°C, and underwent 90 minutes of circulatory arrest. Ketamine-treated canines (n = 5; total dose 2.85 mg/kg) were compared to untreated controls (n = 10). A validated neurobehavioral deficit score was obtained at 24, 48, and 72 hours (0 = no deficits/normal exam; higher score represents increasing deficits). Biomarkers of neuronal injury in the cerebrospinal fluid were examined at baseline and at 8, 24, 48, and 72 hours. Brain histopathologic injury was scored at 72 hours (higher score indicates more necrosis and apoptosis). Ketamine-treated canines had significantly improved, lower neurobehavioral deficit scores compared to controls (overall P = 0.003; 24 hours: median 72 vs 112, P = 0.030; 48 hours: 47 vs 90, P = 0.021; 72 hours: 30 vs 89, P = 0.069). Although the histopathologic injury scores of ketamine-treated canines (median 12) were lower than controls (16), there was no statistical difference (P = 0.10). Levels of phosphorylated neurofilament-H and neuron specific enolase, markers of neuronal injury, were significantly lower in ketamine-treated animals (P = 0.010 and = 0.039, respectively). Ketamine significantly reduced neurologic deficits and biomarkers of injury in canines after hypothermic circulatory arrest. Ketamine represents a safe and approved medication that may be useful as a pharmacologic neuroprotectant during cardiac surgery with circulatory arrest.

Bifurcated Arterial Circulation for Hybrid Aortic Reconstruction: A Novel Technique

Hybrid aortic procedures present many new challenges to the management of cardiopulmonary bypass (CPB). Reoperation or previous thoracic endovascular aortic repair (TEVAR) can further complicate these procedures, increasing the need for flexibility within the CPB system to execute multiple perfusion strategies as cases dictate. This technique describes the use of a bifurcated arterial circulation to provide both cerebral and lower body perfusion during a redo hybrid aortic arch reconstruction. The arterial line was divided into upper and lower body limbs, and connected to an 8-mm Dacron graft to the axillary artery, as well as a percutaneous 16-Fr. OptiSite femoral arterial cannula respectively. A 25-Fr. multi-stage femoral venous cannula was placed percutaneously as well. CPB was initiated utilizing both arterial cannulas with near-infrared spectroscopy and electroencephalogram to monitor the adequacy of cerebral perfusion. Moderate hypothermia of 26°C was induced and a CODA balloon (Cook Medical, Bloomington, IN) was deployed to occlude the proximal limb of a thoracic endovascular repair (TEVAR) graft; the common trunk of the debranched arch vessels was clamped proximally, allowing for simultaneous upper and lower body perfusion. Upon completion of the distal arch, the CODA balloon was removed and total body perfusion was reinitiated via central cannulation utilizing a sidearm on the arch graft.

Anaesthetic-surgical guide in the treatment of ascending aorta and surgery of the ascending aorta and aortic arch. Consensus document of the Spanish Society of Cardiovascular and Endovascular Surgery and the Sociedad of Anaesthesiology, Resuscitation and Pain Therapy

Aortic pathology is always a challenge for the clinician, and must be diagnosed and treated by a multidisciplinary team due to the technical and technological complexity of the resources used. Ongoing efforts to implement a systematic, protocolized approach involving "Aortic teams" made up of cardiologists, cardiac surgeons, vascular surgeons, anaesthesiologists and radiologists, among others are now leading to improved outcomes. The aim of this consensus document drawn up by the Aortic working groups of the Spanish Society of Anaesthesiology, Resuscitation and Pain Therapy (SEDAR) and the Spanish Society of Thoracic and Cardiovascular Surgery (SECTCV) is to disseminate a set of working protocols. The latest consensus document of the European Association for Cardio-Thoracic Surgery (EACTS) and the European Society for Vascular Surgery (ESVS) define the concept of "AORTIC TEAM"(1). The aortic team should be closely involved from diagnosis to treatment and finally follow-up, and should be formed of cardiac and vascular surgeons working together with anaesthesiologists, cardiologists, radiologists and geneticists. Treatment of aortic pathologies should be centralised in large centres, because this is the only way to effectively understand the natural course of the disease, provide the entire range of treatment options under one umbrella and treat potential complications. A streamlined emergent care pathway (24/7 availability), adequate transportation and transfer capabilities, as well as rapid activation of the multidisciplinary team must be available. In light of the complexity and constant evolution of therapeutic options, we present this first version of the Anaesthesiology and surgical guidelines for surgery of the ascending aorta and aortic arch. Some questions will no doubt remain unanswered, and future versions will include new techniques that, though implemented in some centres, are still not widely recommended.

NMDA Receptor Antagonism for Neuroprotection in a Canine Model of Hypothermic Circulatory Arrest

BACKGROUND

Hypothermic circulatory arrest (HCA) is associated with neurologic morbidity, in part mediated by activation of the N-methyl-D-aspartate glutamate receptor causing excitotoxicity and neuronal apoptosis. Using a canine model, we hypothesized that the N-methyl-D-aspartate receptor antagonist MK801 would provide neuroprotection and that MK801 conjugation to dendrimer nanoparticles would improve efficacy.

MATERIALS AND METHODS

Male hound dogs were placed on cardiopulmonary bypass, cooled to 18°C, and underwent 90 min of HCA. Dendrimer conjugates (d-MK801) were prepared by covalently linking dendrimer surface OH groups to MK801. Six experimental groups received either saline (control), medium- (0.15 mg/kg) or high-dose (1.56 mg/kg) MK801, or low- (0.05 mg/kg), medium-, or high-dose d-MK801. At 24, 48, and 72 h after HCA, animals were scored by a standardized neurobehavioral paradigm (higher scores indicate increasing deficits). Cerebrospinal fluid was obtained at baseline, eight, 24, 48, and 72 h after HCA. At 72 h, brains were examined for histopathologic injury in a blinded manner (higher scores indicate more injury).

RESULTS

Neurobehavioral deficit scores were reduced by low-dose d-MK801 on postoperative day two (P < 0.05) and by medium-dose d-MK801 on postoperative day 3 (P = 0.05) compared with saline controls, but free drug had no effect. In contrast, high-dose free MK801 significantly improved histopathology scores compared with saline (P < 0.05) and altered biomarkers of injury in cerebrospinal fluid, with a significant reduction in phosphorylated neurofilament-H for high-dose MK801 versus saline (P < 0.05).

CONCLUSIONS

Treatment with MK-801 demonstrated significant improvement in neurobehavioral and histopathology scores after HCA, although not consistently across doses and conjugates.

Brain Protection in Aortic Arch Surgery: An Evolving Field

Despite advances in cardiac surgery and anesthesia, the rates of brain injury remain high in aortic arch surgery requiring circulatory arrest. The mechanisms of brain injury, including permanent and temporary neurologic dysfunction, are multifactorial, but intraoperative brain ischemia is likely a major contributor. Maintaining optimal cerebral perfusion during cardiopulmonary bypass and circulatory arrest is the key component of intraoperative management for aortic arch surgery. Various brain monitoring modalities provide different information to improve cerebral protection. Electroencephalography gives crucial data to ensure minimal cerebral metabolism during deep hypothermic circulatory arrest, transcranial Doppler directly measures cerebral arterial blood flow, and near-infrared spectroscopy monitors regional cerebral oxygen saturation. Various brain protection techniques, including hypothermia, cerebral perfusion, pharmacologic protection, and blood gas management, have been used during interruption of systemic circulation, but the optimal strategy remains elusive. Although deep hypothermic circulatory arrest and retrograde cerebral perfusion have their merits, there have been increasing reports about the use of antegrade cerebral perfusion, obviating the need for deep hypothermia. With controversy and variability of surgical practices, moderate hypothermia, when combined with unilateral antegrade cerebral perfusion, is considered safe for brain protection in aortic arch surgery performed with circulatory arrest. The neurologic outcomes of brain protection in aortic arch surgery largely depend on the following three major components: cerebral temperature, circulatory arrest time, and cerebral perfusion during circulatory arrest. The optimal brain protection strategy should be individualized based on comprehensive monitoring and stems from well-executed techniques that balance the major components contributing to brain injury.

Endovascular exclusion of the entire aortic arch with branched stent-grafts after surgery for acute type A aortic dissection

Background

The treatment of residual pathology of the aortic arch after surgical repair for type A acute dissection (AAD) represents a therapeutic challenge. Recently, new branched endovascular devices have expanded the possibility of aortic arch stent-grafting (ASG) with proximal landing in zone 0. The aim of this retrospective, single-center study was to evaluate outcomes of patients with a history of surgical repair for AAD undergoing ASG with branched devices.

Methods

We analyzed patients undergoing ASG after treatment for type AAD with 2 different branched devices: Nexus (dual-module, single branch, off-the-shelf) and RelayBranch (single-module, dual branch, custom-made). Before ASG, surgical bypass of supra-aortic vessels was performed according to patient's anatomy and to the selected device. All patients underwent clinical and computed tomography scan evaluation before hospital discharge, at 6 months, and on a yearly basis thereafter.

Results

From March 2017 to April 2019, 4 consecutive patients underwent ASG after surgery for AAD at our institution. Mean time from surgery for AAD to ASG was 20 months. Mean age at the time of ASG was 72 years. Nexus and Relay were implanted in 2 patients each. All patients survived and were successfully discharged. Mean intensive care unit stay and hospital stay were 3 and 19 days, respectively. We did not observe any major adverse events. At a mean follow-up of 28 months, all patients are alive and computed tomography scans showed good anatomic results with no endoleaks.

Conclusions

This preliminary experience shows that ASG after surgery for AAD is feasible and provides encouraging clinical and anatomic early results.