Spinal Cord Protection During Open Repair of Thoracic and Thoracoabdominal Aortic Aneurysms Using Profound Hypothermia and Circulatory Arrest

Hypothermic circulatory arrest versus aortic clamping in thoracic and thoracoabdominal aortic aneurysm repair

BACKGROUND

To compare perioperative and midterm outcomes in thoracic and thoraco-abdominal aortic aneurysm (TAA and TAAA) repair using hypothermic circulatory arrest (HCA) or aortic clamping (AC) with mild hypothermia.

METHODS

From 2012 to 2021 there were 180 open repairs of a TAA or TAAA, of which 90 (50%) were done with HCA and 90 (50%) with aortic clamping with mild hypothermia. The indications for HCA were arch aneurysm, TAA from chronic aortic dissection, and inability to clamp the aorta for proximal anastomosis.

RESULTS

Compared to AC, the HCA group had less prior descending aorta replacement/repair (9.1% vs. 32%, p = 0.0001). Intraoperatively, the HCA group had more TAAs (70% vs. 20%, p < 0.0001) while the AC group had more TAAAs (80% vs. 30%, p < 0.0001). HCA group had longer cardiopulmonary bypass times (242 vs. 181 min, p < 0.0001) but shorter cross-clamp time (39 vs. 120 min, p < 0.0001) and lower temperatures (18°C vs. 34°C, p < 0.0001). Postoperatively, the HCA group had longer intubation times (31 vs. 26 h, p = 0.002), but all other postoperative outcomes including paralysis (2.2% vs. 8.9%, p = 0.08), and operative mortality (4.4% vs. 2.2%, p = 0.68) were similar between HCA and AC groups. Patient age was an independent risk factor for postoperative paralysis (OR 1.07, p = 0.03) while HCA was not significant (OR 0.37, p = 0.21). Five-year survival was similar between HCA and AC groups (85% vs. 80%, p = 0.36).

CONCLUSIONS

Postoperative outcomes and midterm survival were acceptable in thoracic and thoracoabdominal aneurysm patients after HCA or AC. Both HCA and AC with mild hypothermia were valid approaches in TAA/A repair.

Staged total arch replacement, followed by fenestrated-branched endovascular aortic repair, for patients with mega aortic syndrome

OBJECTIVE

The aim of the present study was to review the clinical outcomes of a staged approach using total arch replacement (TAR) with an elephant trunk or a frozen elephant trunk, followed by fenestrated-branched endovascular aortic repair (F-BEVAR) for patients with mega aortic syndrome.

METHODS

We reviewed the clinical data and outcomes of 11 consecutive patients (8 men; mean age, 71 ± 7 years) treated by staged TAR and F-BEVAR from January 2014 to December 2018. The F-BEVAR procedures were performed under a prospective, nonrandomized, physician-sponsored investigational device exemption protocol. All patients had had mega aortic syndrome, defined by an ascending aorta, arch, and extent I-II thoracoabdominal aortic aneurysm. The endpoints were 30-day mortality, major adverse events (MAE), patient survival, freedom from reintervention, and freedom from target vessel instability.

RESULTS

Of the 11 patients, 6 had developed chronic postdissection aneurysms after previous Stanford A (three A₁₁, two A₁₀, one A₉) dissection repair and 5 had had degenerative aneurysms with no suitable landing zone in the aortic arch. The thoracoabdominal aortic aneurysms were classified as extent I in four patients and extent II in seven. One patient had died within 30 days after TAR (9.0%). However, none of the remaining 10 patients who had undergone F-BEVAR had died. First-stage TAR resulted in MAE in three patients (27%), including one spinal cord injury. The mean length of stay was 12 ± 6 days. The mean interval between TAR and F-BEVAR was 245 ± 138 days with no aneurysm rupture during the interval. Second-stage F-BEVAR was associated with MAE in two patients (20%), including spinal cord injury in one patient from spinal hematoma due to placement of a cerebrospinal fluid drain. The mean follow-up period was 14 ± 10 months. At 2 years postoperatively, patient survival, primary patency, secondary patency, and freedom from renal-mesenteric target vessel instability was 80% ± 9%, 94% ± 6%, 100%, and 86% ± 8%, respectively. No aortic-related deaths occurred during the follow-up period. Four patients had required reintervention, all performed using an endovascular approach.

CONCLUSIONS

A staged approach to treatment of mega aortic syndrome using TAR and F-BEVAR is a feasible alternative for selected high-risk patients. Larger clinical experience and longer follow-up are needed.

Spinal cord injury as a complication of thoracic endovascular aneurysm repair

OBJECTIVE

Spinal cord ischemia (SCI) is a devastating complication of thoracic aortic aneurysm repair in the era of thoracic endovascular aneurysm repair (TEVAR). This review aims to clarify the causes of SCI during TEVAR and to propose ways that it may be prevented.

METHODS AND RESULTS

We performed an extensive literature search of SCI during TEVAR. Based on the existing literature, we examined the anatomy of the anterior spinal cord artery, which supplies blood to the anterior aspect of the spinal cord, and discuss reported effective ways to prevent SCI during TEVAR, including augmentation of arterial blood pressure and drainage of cerebrospinal fluid.

CONCLUSION

After reviewing the mechanism of SCI during TEVAR, we evaluated promising preventative measures.

Effects of methylprednisolone on neuroprotective effects of delay hypothermia on spinal cord injury in rat

Study Design

A retrospective study.

Purpose

The aim of this study was to evaluate the effects of delayed hypothermia on spinal cord injuries in rats. In addition, the effect of methylprednisolone on therapeutic window of hypothermia was evaluated.

Overview of Literature

Several studies have demonstrated that early hypothermia is the most effective neuroprotective modality. However, delayed hypothermia seems to be more practical for patients with traumatic spinal cord injuries. A combination of hypothermia and other neuroprotective methods, such as using methylprednisolone, may help extend the therapeutic window of hypothermia.

Methods

One hundred and twenty male rats were categorized into six groups. The rats in five groups were subjected to spinal cord injury using the weight drop method, followed by treatment, consisting of early hypothermia, late hypothermia, late hypothermia plus methylprednisolone, or methylprednisolone only. Biochemical tests including catalase, malondialdehyde, and superoxide level were evaluated in the injured spinal cord. Behavioral functions of the hind limb were evaluated by Basso-Battle-Bresnaham locomotor rating scale and tail-flick tests.

Results

Functional and biochemical evaluation showed both early and late hypothermia had significant neuroprotective effects. The treated groups did not differ significantly from one another in the behavioral tests. Hypothermia had better biochemical results compared to methylprednisolone. Also, methylprednisolone was shown to extend the therapeutic window of delayed hypothermia.

Conclusions

Hypothermia showed a significant neuroprotective effect, which can be improved with further studies optimizing the duration of hypothermia and the rewarming period. Moreover, the therapeutic effect of the delayed hypothermia can be extended by methylprednisolone.

Spinal cord injury following thoracic and thoracoabdominal aortic repairs

Objective

To discuss the currently available approaches to prevent spinal cord injury during thoracic and thoracoabdominal aortic repairs.

Methods

We carried out a PubMed search up to 2013 using the Medical Subject Headings: “aortic aneurysm/surgery” and “spinal cord ischemia”; “aortic aneurysm, thoracic/surgery” and “spinal cord ischemia”; “aneurysm/surgery” and “spinal cord ischemia/cerebrospinal fluid”; “aortic aneurysm/surgery” and “paraplegia”. All 190 original articles satisfying our inclusion criteria were analyzed for incidence, predictors, and other pertinent variables related to spinal cord injury, and we compared the results in recent publications with those in earlier reports.

Results

The mean age of the 38,491 patients was 65.3 ± 4.9 years. The overall incidence of paraplegia and/or paraparesis was 7.1% ± 6.1% (range 0%–32%). The incidence of spinal cord injury before 2000, from 2001 to 2007, and 2008–2013 was 9.0% ± 6.7%, 7.0% ± 6.1%, and 5.9% ± 5.2%, respectively ( p = 0.019). Various predictors of spinal cord injury were identified, extent of disease being the most common. Modification of surgical techniques, use of adjuncts, and better understanding of spinal cord perfusion physiology were attributed to the decrease in postoperative spinal cord injury in recent years.

Conclusions

Spinal cord injury after thoracic and thoracoabdominal aortic repair poses a real challenge to cardiovascular surgeons. However, with evolving surgical strategies, identification of predictors, and use of various adjuncts over the years, the incidence of spinal cord injury after thoracic/thoracoabdominal aortic repair has declined. Embracing a multimodality approach offers a good insight into combating this grave complication.

Anesthetic protection of neurons injured by hypothermia and rewarming: roles of intracellular Ca2+ and excitotoxicity

BACKGROUND

Mild hypothermia is neuroprotective after cerebral ischemia but surgery involving profound hypothermia (PH, temperature less than 18°C) is associated with neurologic complications. Rewarming (RW) from PH injures hippocampal neurons by glutamate excitotoxicity, N-methyl-D-aspartate receptors, and intracellular calcium. Because neurons are protected from hypoxia-ischemia by anesthetic agents that inhibit N-methyl-D-aspartic acid receptors, we tested whether anesthetics protect neurons from damage caused by PH/RW.

METHODS

Organotypic cultures of rat hippocampus were used to model PH/RW injury, with hypothermia at 4°C followed by RW to 37°C and assessment of cell death 1 or 24 h later. Cell death and intracellular Ca were assessed with fluorescent dye imaging and histology. Anesthetic agents were present in the culture media during PH and RW or only RW.

RESULTS

Injury to hippocampal CA1, CA3, and dentate neurons after PH and RW involved cell swelling, cell rupture, and adenosine triphosphate (ATP) loss; this injury was similar for 4 through 10 h of PH. Isoflurane (1% and 2%), sevoflurane (3%) and xenon (60%) reduced cell loss but propofol (3 μM) and pentobarbital (100 μM) did not. Isoflurane protection involved reduction in N-methyl-D-aspartate receptor-mediated Ca influx during RW but did not involve γ-amino butyric acid receptors or KATP channels. However, cell death increased over the next day.

CONCLUSION

Anesthetic protection of neurons rewarmed from 4°C involves suppression of N-methyl-D-aspartate receptor-mediated Ca overload in neurons undergoing ATP loss and excitotoxicity. Unlike during hypoxia/ischemia, anesthetic agents acting predominantly on γ-aminobutyric acid receptors do not protect against PH/RW. The durability of anesthetic protection against cold injury may be limited.

Role of induced hypothermia in thoracoabdominal aortic aneurysm surgery

For more than 50 years, hypothermia has been used in aortic surgery as a tool for neuroprotection. Hypothermia has been introduced into thoracoabdominal aortic aneurysm (TAAA) surgery by many cardiovascular centers to protect the body's organs, including the spinal cord. Numerous publications have shown that hypothermia can prevent immediate and delayed motor dysfunction after aortic cross-clamping. Here, we reviewed the historical application of hypothermia in aortic surgery, role of hypothermia in preclinical studies, cellular and molecular mechanisms by which hypothermia confers neuroprotection, and the role of systemic and regional hypothermia in clinical protocols to reduce and/or eliminate the devastating consequences of ischemic spinal cord injury after TAAA repair.

Descending thoracic aortic surgery: update on mortality, morbidity, risk assessment and management

PURPOSE OF REVIEW

The purpose of this review is to summarize the literature on thoracic aortic surgery, as well as key management guidelines in the perioperative period. This is particularly timely, as endovascular techniques continue to evolve and become more available.

RECENT FINDINGS

Endovascular treatment of thoracic aortic disease is expanding in applications and case complexity.

SUMMARY

With the expanded use of endovascular techniques to treat aortic disease, midterm and long-term outcome studies and comparisons to open surgical approach are now being published with increasing frequency. This review analyzes the available literature on preventing adverse outcomes after descending thoracic aortic surgery, with specific attention to mortality, morbidity, risk assessment and management in the perioperative setting.

Neurological complications of thoracic endovascular aortic repair

Thoracic endovascular aortic repair (TEVAR) has decreased the morbidity and mortality associated with open surgical repair of descending thoracic aortic diseases, but important complications unique to the procedure remain. Spinal cord ischemia and infarction is a recognized complication caused by endovascular coverage or injury to spinal cord collateral vessels. Stroke is a consequence of thromboembolism or coverage of aortic arch branch vessels with insufficient collateral circulation. Understanding the risk factors and the pathophysiology of neurological complications of TEVAR are important for the successful anesthetic and surgical management and treatment of patients undergoing endovascular procedures involving the thoracic aorta.