Fighting spinal cord complication during surgery for thoracoabdominal aortic disease

Prevention of Spinal Cord Injury during Thoracoabdominal Aortic Aneurysms Repair: What the Anaesthesiologist Should Know

Thoraco-abdominal aortic repair is a high-risk surgery for both mortality and morbidity. A major complication is paraplegia-paralysis due to spinal cord injury. Modern thoracic and abdominal aortic aneurysm repair techniques involve multiple strategies to reduce the risk of spinal cord ischemia during and after surgery. These include both surgical and anaesthesiologic approaches to optimize spinal cord perfusion by staging the procedure, guaranteeing perfusion of the distal aorta through various techniques (left atrium–left femoral artery by-pass) by pharmacological and monitoring interventions or by maximizing oxygen delivery and inducing spinal cord hypothermia. Lumbar CSF drainage alone or in combination with other techniques remains one of the most used and effective strategies. This narrative review overviews the current techniques to prevent or avoid spinal cord injury during thoracoabdominal aortic aneurysms repair.

Intravenous injection of adult human bone marrow mesenchymal stromal cells attenuates spinal cord ischemia/reperfusion injury in a murine aortic arch crossclamping model

OBJECTIVE

We sought to investigate the efficacy of human bone marrow mesenchymal stem/stromal cell (hBM-MSC) in a murine spinal cord ischemia/reperfusion (SCIR) model.

METHODS

C57BL/6J mice were subjected to SCIR by crossclamping the aortic arch and left subclavian artery for 5.5 minutes. Two hours after reperfusion, hBM-MSCs (hBM-MSC group) or phosphate-buffered saline (control group) were intravenously injected without immunosuppressant. Hindlimb motor function was assessed until day 28 after reperfusion using the Basso Mouse Scale (BMS). The lumbar spinal cord was harvested at hour 24 and day 28, and the histologic number of NeuN-positive motor neurons in 3 cross-sections of each lumbar spinal cord and the gene expression were evaluated.

RESULTS

BMS score was 0 throughout the study period in all control mice. BMS score was significantly greater in the hBM-MSC group than the control group from hour 8 (P < .05) to day 28 (P < .01). The numbers of motor neurons at hour 24 (P < .01) and day 28 (P < .05) were significantly preserved in the hBM-MSC group than the control group. mRNA expression levels of proinflammatory cytokines were significantly lower (P < .05), and those of insulin-like growth factor-1 (P < .01) and proangiogenic factors (P < .05) were significantly greater in the hBM-MSC group than the control group at hour 24.

CONCLUSIONS

hBM-MSC therapy may attenuate SCIR injury by preserving motor neurons, at least in part, through inhibition of proinflammatory cytokines and upregulation of proangiogenic factors in the reperfusion-injured spinal cord.

Perillaldehyde Alleviates Spinal Cord Ischemia-Reperfusion Injury Via Activating the Nrf2 Pathway

BACKGROUND

Spinal Cord ischemia-reperfusion injury (SCII) is one of the most destructive complications in thoracic-abdominal aortic surgery, which can cause physical abnormalities, paralysis and even brain death. Evidence has shown that perillaldehyde (PAH) can ameliorate rat's cerebra ischemia-reperfusion injury. However, the effect of PAH on SCII remains unknown.

METHODS

The current study established SCII rat models and oxygen and glucose deprivation/reoxygenation-induced BV2 microglia models to explore whether PAH could alleviate SCII symptoms and to investigate underlying mechanism.

RESULTS

SCII rats underwent severe neurologic motor dysfunction and histopathologic injury compared with the normal rats, which are exhibited by loss of motor neurons and decrease of nissl bodies. Treatment with PAH significantly ameliorated motor dysfunction and neuron damage. PAH downregulated the expression of NLR family pyrin domain containing 3, cleaved/pro caspase-1, interleukin-1β and interleukin-18 in spinal cord tissues of SCII rats. Besides, the contents of oxidative stress-related factors superoxide dismutase, manganese-dependent superoxide dismutase, catalase and glutathione peroxidase were significantly increased and malondialdehyde content was decreased after PAH treatment. PAH treatment upregulated the expression of nuclear factor-E2-related factor 2 and heme oxygenase-1 in spinal cord tissues of SCII rats. Our in vitro study confirmed that PAH inhibited microglial activation by activating the nuclear factor-E2-related factor 2/heme oxygenase-1 pathway, exhibited by alleviated inflammation and oxidative stress.

CONCLUSIONS

This study elucidates that PAH has the potential value for treating SCII, which provides an experimental basis for clinical trials in the future.

Interventions to improve perioperative neurologic outcomes

PURPOSE OF REVIEW

Few outcomes in surgery are as important to patients as that of their neurologic status. The purpose of this review is to discuss and categorize the most common perioperative neurologic complications. We will also discuss strategies to help prevent and mitigate these complications for our patients.

RECENT FINDINGS

There are several strategies the anesthesiologist can undertake to prevent or treat conditions, such as perioperative neurocognitive disorders, spinal cord ischemia, perioperative stroke, and postoperative visual loss.

SUMMARY

A thorough understanding of threats to patients' neurologic well-being is essential to excellent clinical practice.

Impact of preservation of the latissimus dorsi muscle through a left anteroaxillary thoracotomy on spinal cord protection in descending thoracic and thoraco-abdominal aortic operations†

OBJECTIVES

The presence of collateral network circulation to the spinal cord, which is reflected in the repair of a descending thoracic aortic aneurysm (dAo) and a thoraco-abdominal aortic aneurysm (TAAo), has been demonstrated in clinical and animal experimental data. The latissimus dorsi muscle (LDM) including the thoracodorsal artery might be one of the major sources of this collateral network. The objective of this study was to evaluate the impact on spinal cord safety of a left anteroaxillary thoracotomy with minimal muscle division including preservation of the LDM in surgery for dAo and TAAo.

METHODS

Sixty-nine patients [64 (23-85) years old; 56 men] who underwent surgical repair for dAo and TAAo were divided into 2 groups: 29 [65 (23-84) years old] with an anteroaxillary thoracotomy with LDM preservation (PL group) and 40 [61 (28-85) years old] with a lateral thoracotomy without LDM preservation (NL group).

RESULTS

Aortic repairs were performed at the dAo in 30 patients including 14 in the PL group vs 16 in the NL group and at the TAAo in 39 patients including 15 in the PL group vs 24 in the NL group. There were 2 (2.9%) 30-day deaths; 2 (7.9%) in the PL group vs none in the NL group (P = 0.173). No strokes occurred. In patients with a femoro-femoral partial cardiopulmonary bypass with mild hypothermia, the incidence of loss of signal of motor-evoked potentials (>50%) was significantly lower in the PL group; 5.6% vs 31.8% (P = 0.039). The frequency of signal reduction of the remaining motor-evoked potential after surgery was also significantly lower in the PL group: 3.7% vs 25% (P = 0.040). Subsequently, the rate of spinal cord complications were lower in the PL group: 3.4% vs 12.5% (P = 0.188).

CONCLUSIONS

The left anteroaxillary thoracotomy with minimal incision of the muscles including the LDM might have potential advantages for spinal cord protection via preserved intramuscular collateral circulations to the spinal cord in dAo/TAAo open repairs.

Biomechanical characterization of a novel ring connector for sutureless aortic anastomosis

The surgical treatment for aortic diseases remains a challenge for any cardiac surgeon. The use of sutureless ring connector in aortic anastomosis can simplify the procedure and shorten anastomosis time. Therefore, we developed a novel device for sutureless aortic anastomosis. A series of experiments were carried out for tensile and leakproof-capacity assessments to verify the feasibility of the ring connector by using fresh swine aorta samples. In in vivo test, the ring connector was implanted in 6 swine with follow-up of 6 months. Radiographic and pathological studies of the aorta were performed. In the tensile tests, the strength was 32.7±5.9 Newton (N) in the sutureless anastomosis group, compared with 73.3±12.5 N in the control group by traditional manual suture. In the leakproof-capacity assessment, no sign of either leakage or bursting was evident at 280 mmHg of internal pressure in the aorta samples. In in vivo tests, it took 9.47±0.3 minutes for the sutureless anastomosis, compared with 15.58±1.39 minutes for hand-sewn suturing. Insertion was easy and rapid. Radiographic and pathological studies were performed at first month, third month and sixth month after surgery, each time obtained from the two swine, showed patency of the anastomosis and no signs of stenosis, blood leakage, migration or pseudoaneurysm formation, except one paralyzed swine developed of thrombo-occlusion at the site of the sutureless anastomosis. The result indicates that this novel ring connector offers considerable promise for sutureless aortic anastomosis.

Optimized induction of beta common receptor enhances the neuroprotective function of erythropoietin in spinal cord ischemic injury

BACKGROUND

Paraplegia remains the most feared complication of complex thoracoabdominal aortic intervention. Although erythropoietin (EPO) has demonstrated neuroprotective effects in spinal cord ischemia, it does not work until expression of the beta common receptor subunit of the EPO receptor (βcR) is induced by ischemia. We hypothesized that the βcR can be induced by diazoxide (DZ), amplifying the neuroprotective effects of EPO in spinal cord ischemia-reperfusion injury.

METHODS

For the DZ time trial, adult male C57/BL6 mice received DZ (20 mg/kg) by oral gavage. Spinal cords were harvested after 0, 12, 24, 36, and 48 hours of administration. To evaluate optimal dosing, DZ was administered at 0, 5, 10, 20, and 40 mg/kg. The expression of βcR was assessed by Western blot analysis. Five groups were studied: PBS (pretreatment)+PBS (immediately before), PBS+EPO, DZ+PBS, DZ+EPO, and sham (without cross-clamping). Spinal cord ischemia was induced by 4 minutes of thoracic aortic cross-clamping. Functional scoring (Basso Mouse Score) was done at 12-hour intervals for 48 hours, and spinal cords were harvested for histological analysis.

RESULTS

Western blot analysis demonstrated that optimal βcR up-regulation occurred at 36 hours after DZ administration, and the optimal DZ dosage for βcR induction was 20 mg/kg. Motor function at 48 hours after treatment was significantly better preserved in the DZ+EPO group compared with all other groups, and was significantly better preserved in the DZ only and EPO only groups compared with control (PBS+PBS).

CONCLUSIONS

Pharmacologic up-regulation of βcR with DZ can increase the efficacy of EPO in preventing spinal cord ischemia and reperfusion injury. Improved understanding of this synergetic mechanism may serve to further prevent ischemic complications for high-risk aortic intervention.

Reproducible Motor Deficit Following Aortic Occlusion in a Rat Model Of Spinal Cord Ischemia

Spinal cord ischemia is a fatal complication following thoracoabdominal aortic aneurysm surgery. Researchers can investigate the strategies for preventing and treating this complication using experimental models of spinal cord ischemia. The model described here demonstrates varying degrees of paraplegia that relate to the length of occlusion following thoracic aortic occlusion in a rat spinal cord ischemia model. A 2-Fr. balloon-tipped catheter was advanced through the femoral artery into the descending thoracic aorta until the catheter tip was placed at the left subclavian artery in anesthetized male Sprague-Dawley rats. Spinal cord ischemia was induced by inflating the catheter balloon. After a set period of occlusion (9, 10, or 11 min), the balloon was deflated. Neurologic assessment was performed using the motor deficit index at 24 h after surgery, and the spinal cord was harvested for histopathological examination. Rats that underwent 9 min of aortic occlusion showed mild and reversible motor impairment in the hind limb. Rats subjected to 10 min of aortic occlusion presented with moderate but reversible motor impairment. Rats subjected to 11 min of aortic occlusion displayed complete and persistent paralysis. The motor neurons in the spinal cord sections were more preserved in rats subjected to shorter duration of aortic occlusion. Researchers can achieve a reproducible hind limb motor deficit following thoracic aortic occlusion using this spinal cord ischemia model.

Modification of a Standard Thoracoabdominal Incision to Preserve Collaterals to Adamkiewicz Artery

We report a case of a 35-year-old male who underwent thoracoabdominal aortic repair of a chronic dissecting aortic aneurysm, Crawford extent II. Preoperative computed tomography showed thrombosis of almost all intercostal arteries. Precise diagnostic assessment demonstrated the Adamkiewicz artery originating from the left lateral thoracic artery and subscapular artery, which would have been at risk after using a standard Stoney's incision, thus potentially causing paraplegia or paraparesis due to spinal cord ischemia. We modified the lateral thoracic incision anteriorly and successfully preserved the collateral arteries without impairing the spinal cord function.

Current and emerging treatment options for spinal cord ischemia

Spinal cord infarction (SCI) is a rare but disabling disorder caused by a wide spectrum of conditions. Given the lack of randomized-controlled trials, contemporary treatment concepts are adapted from guidelines for cerebral ischemia, atherosclerotic vascular disease, and acute traumatic spinal cord injury. In addition, patients with SCI are at risk for several potentially life-threatening but preventable systemic and neurologic complications. Notably, there is emerging evidence from preclinical studies for the use of neuroprotection in acute ischemic injury of the spinal cord. In this review, we discuss the current state of the art for the therapy and prevention of SCI and highlight potential emerging treatment concepts awaiting translational adoption.

Straight incision for extended descending and thoracoabdominal aortic replacement: novel and simple exposure with rib-cross thoracotomy

OBJECTIVES

Spiral incision of the thoracic wall towards the tip of a scapula and approach through the sixth intercostal space has been a standard method for the replacement of thoracoabdominal and descending aortic aneurysms. However, the exposure of the proximal lesion of the aorta with the spiral incision is not always sufficient for patients with a lesion extending into the aortic arch. Patients with Marfan syndrome tend to have a flat chest, and exposure using left thoracotomy generally causes difficulty to operate on the aortic arch.

METHODS

Since May 2012, 47 patients (mean age 51.2 ± 16.1, range 9-79, 33 males) have received a novel incision for better exposure of the extended descending and thoracoabdominal aneurysm. A straight incision instead of the traditional spiral one was made from the axilla to the umbilical region and the fourth to sixth ribs were transected. The latissimus dorsi muscle and thoracodorsal artery were preserved, which could be a source for collateral circulation to the Adamkiewicz artery. There were two emergent operations for acute aortic dissection. Twenty-four patients (51%) had undergone previous proximal aortic operation, and 2 patients undergone debranched thoracic endovascular aneurysm repair of the aortic arch. Connective tissue disorders were diagnosed in 16 (34.0%) patients (Marfan syndrome 13, Loeys-Dietz syndrome 3). All surgeries were performed under profound hypothermia.

RESULTS

Seven patients underwent total descending aortic replacement, and the others had Type II thoracoabdominal aortic replacements. Three had partial aortic arch replacement, 5 had total aortic arch replacement and 3 had Y-grafting for the abdominal aorta concomitantly. Operation time was 567 ± 141 min and cardiopulmonary bypass time was 259 ± 60 min. Three patients had a major stroke (6.4%), and 1 had a minor stroke. There was no spinal cord complication among survivors. Hospital mortality rate was 4.3% (2/47). These 2 patients underwent thoracoabdominal aortic replacement, and had a major stroke.

CONCLUSIONS

This new exposure with straight incision with rib-cross thoracotomy provided excellent exposures for the long segment of the thoracoabdominal aorta, and it enabled extended replacement from the ascending aorta to the abdominal aorta.

Effects of adenosine monophosphate-activated kinase in the ventral horn of rabbit spinal cord after transient ischemia

OBJECTIVE

To investigate the effect compound C, an adenosine monophosphate-activated kinase (AMPK) inhibitor, has on motor neurons of rabbit spinal cord after ischemia/reperfusion.

DESIGN

Compound C (30 mg/kg) was administered intraperitoneally to rabbits 30 minutes before ischemia and the animals were sacrificed at 15 minutes after ischemia/reperfusion to measure lactate levels and at 72 hours after ischemia/reperfusion for morphological study.

RESULTS

The administration of compound C did not produce any significant changes in physiological parameters such as pH, arterial blood gas (PaCO(2) and PaO(2)), and blood glucose in rabbit either at 10 minutes before ischemia or at 10 minutes after reperfusion. However, the administration of compound C did significantly ameliorate lactate acidosis at 15 minutes after reperfusion. In addition, the administration of compound C significantly improved the neurological scores of the rabbits and reduced the neuronal death seen in the ventral horn of their spinal cords at 72 hours after ischemia/reperfusion.

CONCLUSIONS

Inhibition of AMPK can ameliorate the ischemia-induced neuronal death in the spinal cord via the reduction of early lactate acidosis.

How to prevent spinal cord injury during endovascular repair of thoracic aortic disease

The incidence of spinal cord injury in thoracic endovascular aortic repair (TEVAR) has been 3-5 % from recent major papers where sacrifice of the critical intercostal arteries is inevitable by a stent graft. Hemodynamic stability, which depends on a network of blood vessels around the cord is most important not only during but also after stent-graft deployment. High risk factors of spinal cord injury during endovascular aortic repair are (1) coverage of the left subclavian artery, (2) extensive coverage of long segments of the thoracic aorta, (3) prior downstream aortic repair, (4) compromising important intercostal (T8-L1), vertebral, pelvic and hypogastric collaterals, and (5) shaggy aorta. Preoperative, intraoperative, and postoperative managements have been required to prevent spinal cord injury with TEVAR. For imaging assessment of blood supply to spinal cord including Adamkiewicz artery, prophylactic cerebrospinal fluid drainage is mandatory, and monitoring motor-evoked potential is recommended for high risk factors of spinal cord injury. Mean arterial pressure should be maintained over 90 mmHg after stent-graft placement for a while to prevent delayed spinal cord ischemia in high-risk patients of spinal cord ischemia. Finally, because spinal cord injury during TEVAR is not rare and negligible, perioperative care during TEVAR should be strictly performed according to the protocol proposed by each cardiovascular team.

Reproducable paraplegia by thoracic aortic occlusion in a murine model of spinal cord ischemia-reperfusion

BACKGROUND

Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered advancements to decrease the occurrence this injury. The current model demonstrates reproducible lower extremity paralysis following thoracic aortic occlusion.

METHODS

Adult male C57BL6 mice were anesthetized with isoflurane. Through a cervicosternal incision the aorta was exposed. The descending thoracic aorta and left subclavian arteries were identified without entrance into pleural space. Skeletonization of these arteries was followed by immediate closure (Sham) or occlusion for 4 min (moderate ischemia) or 8 min (prolonged ischemia). The sternotomy and skin were closed and the mouse was transferred to warming bed for recovery. Following recovery, functional analysis was obtained at 12 hr intervals until 48 hr.

RESULTS

Mice that underwent sham surgery showed no observable hind limb deficit. Mice subjected to moderate ischemia for 4 min had minimal functional deficit at 12 hr followed by progression to complete paralysis at 48 hr. Mice subjected to prolonged ischemia had an immediate paralysis with no observable hind-limb movement at any point in the postoperative period. There was no observed intraoperative or post operative mortality.

CONCLUSION

Reproducible lower extremity paralysis whether immediate or delayed can be achieved in a murine model. Additionally, by using a median sternotomy and careful dissection, high survival rates, and reproducibility can be achieved.

Dose-effects of aorta-infused clenbuterol on spinal cord ischemia-reperfusion injury in rabbits

Background

The β₂ adrenergic receptor (β₂AR) plays an important role in ischemia-reperfusion (I/R) injury in various organs. Recently, a selective β₂AR agonist clenbuterol was suggested to protect against cerebral I/R injury. This study was designed to investigate changes of β₂ARs after spinal cord I/R injury and dose-effects of aorta-infused clenbuterol on spinal cord I/R injury in rabbits.

Methods

Spinal cord ischemia was induced in New Zealand white rabbits by infrarenal abdominal aortic occlusion with a balloon catheter for 30 minutes except the sham group. During occlusion, nothing (I/R group), normal saline (NS group) or clenbuterol at different doses of 0.005, 0.01, 0.05, 0.1, 0.5, or 1 mg/kg (C_0.005, C_0.01, C_0.05, C_0.1, C_0.5, and C₁ groups) was infused into the occluded aortic segments. The hemodynamic data, blood glucose and serum electrolytes were measured during experimental period. Neurological function was assessed according to the modified Tarlov scales until 48 hours after reperfusion. After that, the lumbar spinal cord was harvested for β₂AR immunohistochemistry and histopathologic evaluation in the anterior horns.

Results

The β₂AR expression in the anterior horns of the spinal cord was significantly higher in the I/R group than in the sham group. Tarlov scores and the number of viable α-motor neurons were higher in C_0.01-C_0.5 groups than in the NS group, C_0.005 and C₁ groups and were highest in the C_0.1 group. Hypotension and hyperglycemia were found in the C₁ group.

Conclusion

β₂ARs in the anterior horn were upregulated after spinal cord I/R injury. Aortic-infused clenbuterol (0.01–0.5 mg/kg) can attenuate spinal cord I/R injury dose-dependently during the ischemic period. The Optimal dosage was 0.1 mg/kg. Activation of β₂AR could be a new therapeutic strategy for the treatment of spinal cord I/R injury.

One-stage repair of extensive aortic aneurysms: mid-term results with total or subtotal aortic replacement

OBJECTIVES

To retrospectively analyse the mid-term clinical results of one-stage repair of extensive aortic aneurysms with total or subtotal aortic replacement.

METHODS

From February 2004 to February 2011, 21 patients with extensive aortic aneurysm underwent one-stage total or subtotal aortic replacement for aortic dissection (95.23%) or aortic aneurysms. Operations were performed under circulatory arrest with profound hypothermia. Patients were opened with a mid-sternotomy and a thoraco-abdominal incision. Extracorporeal circulation was instituted as usual. During cooling, the ascending aorta or aortic root was replaced. At the nasopharyngeal temperature of 20°C, the aortic arch was replaced with selective antegrade cerebral perfusion. Staged aortic occlusions allowed for replacement of the descending thoracic and abdominal aorta. T6 to T12 intercostal arteries and L1,L2 lumbar arteries were formed to a neo-intercostal artery in place and were connected to an 8-mm branch for maintaining spinal cord blood perfusion. Visceral arteries were joined into a patch and anastomosed to the end of the main graft.

RESULTS

The early mortality was 4.8% (1 of 21); 1 patient died due to renal failure and multiple organ failure. No patient had spinal cord deficits postoperatively. Two patients had postoperative stroke at Day 5 and 7, respectively. Twenty patients were all alive with good life status during the follow-up period ranging from 18 to 84 months postoperatively. One patient was reoperated with aortic valve replacement because of massive valve insufficiency after 2 years. During the follow-up period, reconstructed intercostal arteries were clogged in 3 patients and dilatated in 2 patients with Marfan syndrome.

CONCLUSIONS

One-stage repair of extensive aortic aneurysms with total or subtotal aortic replacement is safe and effective. It is feasible with acceptable surgical risks and satisfactory results. It can eliminate the risk of remnant aortic aneurysm rupture in staged total aortic replacement and has satisfactory mid-term results.

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.