Anesthetic consideration for descending thoracic aortic aneurysm repair

Assessment of the neuroprotective effects of (-)-epigallocatechin-3-gallate on spinal cord ischemia-reperfusion injury in rats

Objective: Paraplegia or paraparesis due to spinal cord ischemia is one of the complications following thoracoabdominal aortic surgery. Recent studies revealed the neuroprotective effects of (-)-epigallocatechin-3-gallate (EGCG) on a variety of neurological disorders. The purpose of this study was to determine the neuroprotective effects of EGCG following spinal cord ischemia-reperfusion injury (IRI).Design: The present study was conducted on four groups of rats each as follows: Sham-operated group (laparotomy alone); Control group (with IRI); EGCGI group (50-mg/kg, i.p., before IRI), and EGCGII group (50-mg/kg, i.p., after IRI). Neurological function evaluated with motor deficit index (MDI) test. Spinal cord samples were taken 48 h after IRI and studied for determination of malodialdehyde (MDA) level, histopathology, and immunohistochemistry of caspase-3, TNF-α, and iNOS.Setting: Mazandaran University of Medical Sciences, Sari, Iran.Results: The level of MDA was significantly decreased in EGCG-treated rats. Attenuated caspase-3, TNF-α, and iNOS expression could be significantly detected in the EGCG-treated rats. Also, EGCG reduced the extent of degeneration of the spinal cord neurons, in addition to a significant reduction of MDI.Conclusion: The results suggest that pre- and post-treatment with EGCG may be effective in protecting spinal cord from IRI.

Kidney protection in thoracoabdominal aortic aneurysm surgery

Acute kidney injury (AKI) is a common complication of both open and endovascular repair of thoracoabdominal aortic aneurysms (TAAA). Its definition varies across difference studies, some standardized definitions (RIFLE, AKIN, KDIGO) have been proposed but still not uniformly employed in published papers. Acute kidney injury is multifactorial and is associated with increased in-hospital mortality, long-term mortality and late renal function decline. In addition, AKI is also associated with perioperative spinal cord ischemia. No specific pharmacological strategy has received a strong recommendation with high level of evidence as a protective measure. Fenoldopam, methylprednisolone or mannitol use to prevent AKI is commonly employed, but not supported by literature data. Avoiding nephrotoxic drugs and maintaining an adequate MAP, during and after the procedure plays a key role in preserving kidney function. During open TAAA surgery, renal arteries may be reimplanted using different techniques. The choice of the best option must be tailored to the patient, to reduce ischemic time and guarantee long-term patency. Current experience suggests that cold crystalloid solutions are the best substrates in preventing ischemia-reperfusion injury. Renal perfusion using Custodiol^® (Dr Franz-Kohler Chemie GmbH; Bensheim, Germany) 4 °C, even if currently considered off-label, represents an encouraging organ protection tool. In endovascular TAAA repair, techniques such as fusion imaging, use of diluted contrast, and CO<inf>2</inf> subtraction angiography have the potential to reduce postoperative AKI. Visceral vessels patency is closely related to the anatomy. Therefore, accurate endograft design according to these characteristics is crucial for long-term preservation of renal function.

Anaesthetic management in endovascular total aortic arch repair via needle-based in situ fenestration: a case series of 14 patients

Objective

Endovascular total aortic arch repair (ETAAR) via needle-based in situ fenestration (ISF) is a major challenge for anaesthesiologists because of haemodynamic instability and the risk of cerebral hypoxia. We herein summarise our experience with anaesthetic management of patients who underwent this procedure.

Methods

Fourteen patients who underwent ETAAR via ISF for arch pathologies involving the major supra-arch branches were included. Regional cerebral oxygen saturation was measured to monitor cerebral perfusion. Partial extracorporeal circulation (EC) support from the right common femoral vein to the right axillary artery was introduced to provide cerebral perfusion.

Results

During ISF, vessel rupture occurred in three patients and ventricular fibrillation occurred in one patient. The regional cerebral oxygen saturation significantly decreased during the potential risk period for cerebral ischaemia. Establishment of EC effectively prevented cerebral ischaemia.

Conclusions

During ETAAR, the risks of haemodynamic instability caused by the procedure and vessel rupture during ISF need to be overcome. Partial EC ensured good cerebral protection in our study, and regional cerebral oxygen saturation monitoring may help to reduce the rate of desaturation.

The roles of chemokine (C-X-C motif) ligand 13 in spinal cord ischemia-reperfusion injury in rats

Spinal cord ischemia-reperfusion injury (SCII) remains an unresolved complication and its underlying mechanism has not been fully elucidated. In this study, we studied the role of chemokine (C-X-C motif) ligand 13 (CXCL13) in a rat model of SCII. We examined the time course and cellular distribution of CXCL13 protein in rats after SCII. The effects of siRNA targeting CXCL13 or C-X-C chemokine receptor type 5 (CXCR5) in SCII were also investigated. Neurological function, histological assessment, and disruption of the blood-spinal cord barrier (BSCB) were evaluated. The expression levels of CXCL13, CXCR5, phosphorylated extracellular signal-regulated kinase (p-ERK), caspase-3, interleukin 6 (IL-6), TNF-α, and IL-1β were determined. We found that SCII resulted in impaired hind limb function and increased the expression of CXCL13. In addition, CXCL13 expression demonstrated the most pronounced effect at 24 h after SCII. We reveal that CXCL13 protein was co-expressed with the mature neuron marker NeuN and the microglial marker IBA-1 in spinal cord tissues of model rats. SCII also increased the expression of CXCR5, p-ERK, caspase-3, IL-6, TNF-α, and IL-1β at 24 h after SCII. Pre-treatment with CXCL13 siRNA protected the rats against SCII and decreased the expression of signalling pathway proteins and proinflammatory cytokines mentioned above. CXCR5 siRNA also showed similar protective effects. These findings indicate that CXCL13 is involved in SCII. The CXCL13/CXCR5 axis promotes the development of SCII, possibly via ERK-mediated pathways. Targeting the mechanism of CXCL13 involved in the development of SCII might be a potential approach for the treatment of this condition.

Thoracoabdominal Aortic Aneurysm Repair: What Should the Anaesthetist Know?

The surgical repair of descending thoracic aortic (DTA) and thoracoabdominal aortic aneurysms (TAAAs) presents one of the greatest challenges for anaesthesiologists. The challenge comes from the fine balance of complex medical issues in the setting of altered physiology that occurs during the perioperative period. Patients presenting for TAAA repair usually have multiple pre-existing comorbid conditions involving their cardiac, pulmonary and renal systems; and aneurysm repair poses a direct and immediate threat to these systems in addition to that to the gastrointestinal and neurologic systems. Operative mortality in thoracoabdominal aortic surgery is quite high to the extent of 5%-12% with a 5-year survival rate of 70%-79% for DTA aneurysm and 59% for thoracoabdominal aortic aneurysm surgeries. Complex haemodynamic changes associated with the clamping and declamping of aorta requires thorough knowledge and expertise for the management of TAAA. We present a brief review on the anaesthetic management and possible complications that anaesthetists should be aware of during TAAA repair.

KIF6 719Arg Genetic Variant and Risk for Thoracic Aortic Dissection

BACKGROUND

Carriers of the 719Arg variant in KIF6, compared with noncarriers, have been reported to be at greater risk for coronary heart disease (CHD) in six prospective studies. Because CHD, thoracic aortic dissection, and nondissection thoracic aortic aneurysm share some risk factors and aspects of pathophysiology, we investigated whether carriers of the 719Arg variant also have greater odds of thoracic aortic dissection or nondissected thoracic aortic aneurysm than noncarriers.

METHODS

We genotyped 140 thoracic aortic dissection cases, 497 nondissection thoracic aortic aneurysm cases, and 275 disease-free controls collected in the United States, Hungary, and Greece and investigated the association between KIF6 719Arg carrier status and thoracic aortic dissection, and between KIF6 719Arg carrier status and nondissection thoracic aortic aneurysm, using logistic regression models adjusted for age, sex, hypertension, smoking, and country.

RESULTS

The odds of aortic dissection were two-fold greater in KIF6 719Arg carriers compared with noncarriers (odds ratio (OR) 2.14, 95% confidence interval (CI) 1.18-3.9). To account for the potential of concomitant CHD to confound the association between the KIF6 719Arg and thoracic aortic dissection, we repeated the analysis after removing subjects with concomitant CHD; the estimates for association of KIF6 719Arg carrier status remained essentially the same (OR 2.04, 95% CI 1.11-3.77). In contrast, KIF6 719Arg carrier status was not associated with risk for nondissection thoracic aortic aneurysm.

CONCLUSIONS

We observed an association of the KIF6 719Arg genetic variant with thoracic aortic dissection in this multicenter case-control study. This association may enhance our management of patients with thoracic aortic disease.

Propofol injection combined with bone marrow mesenchymal stem cell transplantation better improves electrophysiological function in the hindlimb of rats with spinal cord injury than monotherapy

The repair effects of bone marrow mesenchymal stem cell transplantation on nervous system damage are not satisfactory. Propofol has been shown to protect against spinal cord injury. Therefore, this study sought to explore the therapeutic effects of their combination on spinal cord injury. Rat models of spinal cord injury were established using the weight drop method. Rats were subjected to bone marrow mesenchymal stem cell transplantation via tail vein injection and/or propofol injection via tail vein using an infusion pump. Four weeks after cell transplantation and/or propofol treatment, the cavity within the spinal cord was reduced. The numbers of PKH-26-positive cells and horseradish peroxidase-positive nerve fibers apparently increased in the spinal cord. Latencies of somatosensory evoked potentials and motor evoked potentials in the hindlimb were noticeably shortened, amplitude was increased and hindlimb motor function was obviously improved. Moreover, the combined effects were better than cell transplantation or propofol injection alone. The above data suggest that the combination of propofol injection and bone marrow mesenchymal stem cell transplantation can effectively improve hindlimb electrophysiological function, promote the recovery of motor funtion, and play a neuroprotective role in spinal cord injury in rats.

Sevoflurane preconditioning ameliorates neuronal deficits by inhibiting microglial MMP-9 expression after spinal cord ischemia/reperfusion in rats

Background

Microglia are the primary immune cells of the spinal cord that are activated in response to ischemia/reperfusion (IR) injury and release various neurotrophic and/or neurotoxic factors to determine neuronal survival. Among them, matrix metalloproteinase-9 (MMP-9), which cleaves various components of the extracellular matrix in the basal lamina and functions as part of the blood spinal cord barrier (BSCB), is considered important for regulating inflammatory responses and microenvironmental homeostasis of the BSCB in the pathology of ischemia. Sevoflurane has been reported to protect against neuronal apoptosis during cerebral IR. However, the effects of sevoflurane preconditioning on spinal cord IR injury remain unclear. In this study, we investigated the role of sevoflurane on potential genetic roles of microglial MMP-9 in tight junction protein breakdown, opening of the BSCB, and subsequent recruitment of microglia to apoptotic spinal cord neurons.

Results

The results showed significant upregulation of MMP-9 in rats with IR-induced inflammation of the BSCB compared to that of the sham group, manifested as dysfunctional BSCB with increased Evans blue extravasation and reduced expression of occludin protein. Increased MMP-9 expression was also observed to facilitate invasion and migration of activated microglia, imaging as high Iba-1 expression, clustered to neurons in the injured spinal cord, as shown by double immunofluorescence, and increased proinflammatory chemokine production (CXCL10, CCL2). Further, sevoflurane preconditioning markedly improved motor function by ameliorating neuronal apoptosis, as shown by reduced TUNEL-positive cell counts and expression of cleaved caspase-3. These protective effects were probably responsible for downregulation of MMP-9 and maintenance of normal expression of occludin protein indicating BSCB integrity from inflammatory damage, which was confirmed by decreased protein levels of Iba-1 and MMP-9, as well as reduced production of proinflammatory chemokines (CXCL10, CCL2) and proinflammatory cytokines (IL-1β). Intrathecal injection of specific siRNAs targeting MMP-9 had similar protective effects to those of sevoflurane preconditioning.

Conclusions

Preconditioning with 2.4% sevoflurane attenuated spinal cord IR injury by inhibiting recruitment of microglia and secretion of MMP-9; thus inhibiting downstream effects on inflammatory damage to BSCB integrity and neuronal apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-014-0069-7) contains supplementary material, which is available to authorized users.

Role of the TLR4 pathway in blood-spinal cord barrier dysfunction during the bimodal stage after ischemia/reperfusion injury in rats

Background

Spinal cord ischemia-reperfusion (I/R) involves two-phase injury, including an initial acute ischemic insult and subsequent inflammatory reperfusion injury, resulting in blood-spinal cord barrier (BSCB) dysfunction involving the TLR₄ pathway. However, the correlation between TLR₄/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in BSCB dysfunction is not fully understood. The aim of this study is to characterize inflammatory responses in spinal cord I/R and the events that define its clinical progression with delayed neurological deficits, supporting a bimodal mechanism of injury.

Methods

Rats were intrathecally pretreated with TAK-242, MyD₈₈ inhibitory peptide, or Resveratrol at a 12 h interval for 3 days before undergoing 14-minute occlusion of aortic arch. Evan’s Blue (EB) extravasation and water content were detected at 6, 12, 18, 24, 36, 48, and 72 h after reperfusion. EB extravasation, water content, and NF-κB activation were increased with time after reperfusion, suggesting a bimodal distribution, as maximal increasing were detected at both 12 and 48 h after reperfusion. The changes were directly proportional to TLR₄ levels determined by Western blot. Double-labeled immunohistochemical analysis was also used to detect the relationship between different cell types of BSCB with TLR₄. Furthermore, NF-κB and IL-1β were analyzed at 12 and 48 h to identify the correlation between MyD₈₈-dependent and TRIF-dependent pathways.

Results

Rats without functional TLR₄ and MyD₈₈ attenuated BSCB leakage and inflammatory responses at 12 h, suggesting the ischemic event was largely mediated by MyD₈₈-dependent pathway. Similar protective effects observed in rats with depleted TLR₄, MyD₈₈, and TRIF receptor at 48 h infer that the ongoing inflammation which occurred in late phase was mainly initiated by TRIF-dependent pathway and such inflammatory response could be further amplified by MyD₈₈-dependent pathway. Additionally, microglia appeared to play a major role in early phase of inflammation after I/R injury, while in late responding phase both microglia and astrocytes were necessary.

Conclusions

These findings indicate the relevance of TLR₄/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in bimodal phases of inflammatory responses after I/R injury, corresponding with the clinical progression of injury and delayed onset of symptoms. The clinical usage of TLR₄ signaling inhibitors at different phases may be a therapeutic option for the prevention of delayed injury.

One-lung ventilation for surgical repair of thoracic aortic aneurysm

Advances in the surgical approach to thoracic aortic aneurysm repairs have led to the increasing use of one-lung ventilation. Today's practice of cardiothoracic and vascular anesthesia requires a clear understanding of the techniques available for lung separation and the technical skills necessary to employ them. In this article, we discuss and evaluate the options for one-lung ventilation in thoracic aortic aneurysm repair with regard to preoperative, intraoperative, and postoperative management.

Glycyrrhizin attenuates rat ischemic spinal cord injury by suppressing inflammatory cytokines and HMGB1

AIM

To investigate the neuroprotective effect of glycyrrhizin (Gly) against the ischemic injury of rat spinal cord and the possible role of the nuclear protein high-mobility group box 1 (HMGB1) in the process.

METHODS

Male Sprague-Dawley rats were subjected to 45 min aortic occlusion to induce transient lumbar spinal cord ischemia. The motor functions of the animals were assessed according to the modified Tarlov scale. The animals were sacrificed 72 h after reperfusion and the lumbar spinal cord segment (L2-L4) was taken out for histopathological examination and Western blotting analysis. Serum inflammatory cytokine and HMGB1 levels were analyzed using ELISA.

RESULTS

Gly (6 mg/kg) administered intravenously 30 min before inducing the transient lumbar spinal cord ischemia significantly improved the hind-limb motor function scores, and reduced the number of apoptotic neurons, which was accompanied by reduced levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the plasma and injured spinal cord. Moreover, the serum HMGB1 level correlated well with the serum TNF-α, IL-1β and IL-6 levels during the time period of reperfusion.

CONCLUSION

The results suggest that Gly can attenuate the transient spinal cord ischemic injury in rats via reducing inflammatory cytokines and inhibiting the release of HMGB1.

Magnesium sulfate does not protect spinal cord against ischemic injury

OBJECTIVE

We tested various doses of MgSO(4) to investigate the effect of Mg on a spinal cord ischemia.

METHODS

Rats were treated with either MgSO(4) (30, 100, or 300 mg/kg; group Mg(low), group Mg(medium), group Mg(high), respectively, n = 10 for each) or saline (control group; n = 10) before ischemia. Spinal cord ischemia was induced using a balloon-tipped catheter placed on proximal descending aorta. During surgery, hemodynamic variables were recorded before ischemia, during aortic occlusion and after reperfusion. Neurologic function was assessed using the motor deficit index (MDI; 0 = normal, 6 = complete paralysis) until seven days after reperfusion, and histologic examination of spinal cord was performed.

RESULTS

After reperfusion, the mean arterial pressure in the group Mg(high) was significantly lower than other groups. Compared to the control group, the groups Mg(low) and Mg(medium) did not show any difference in MDI and the group Mg(high) showed significantly higher MDI. The number of normal motor neurons was similar among other groups except the group Mg(high) had a significantly fewer normal motor neurons.

CONCLUSIONS

Intravenous MgSO(4) with low or medium dose (30, or 100 mg/kg) did not improve neurological injury following spinal cord ischemia. Furthermore, higher dose of MgSO(4) (300 mg/kg) resulted in hemodynamic instability and aggravated neurologic outcome.

[Spinal cord protection during open and endovascular surgery in thoracic and thoracoabdominal aorta diseases]

In recent decades great advances have been made in surgical procedures for treating thoracic and thoracoabdominal aorta defects. Associated mortality and morbidity rates have dropped considerably, mainly in major reference centers, but nonetheless continue to be significant. The need for new strategies to reduce mortality and morbidity has made endovascular approaches an attractive alternative for high-risk surgical patients. The most feared complications of these procedures include paraparesis and paraplegia, which have devastating consequences on patients' quality of life. We provide an updated review of the pathophysiology of spinal cord ischemia in open and endovascular surgery, as well as perioperative measures designed to protect the spinal cord in both types of procedure.

A case of difficulty predicting neurological deficit during thoracoabdominal aortic surgery

Perioperative spinal cord injury associated with thoracoabdominal aorta (TAAA) surgery is a devastating complication. With variable results, the intraoperative use of neurophysiologic monitoring has been employed for the diagnosis and prevention of spinal cord ischemia. We present a case report of a patient undergoing TAAA surgery with the use of evoked potential monitoring. Intraoperatively, both sensory and motor evoked potentials were utilized and consequently the patient experienced changes in monitoring consistent with a new neurologic deficit. However, postoperatively these changes in evoked potentials never manifested in neurologic injury. We examine the utility of neurophysiologic monitoring as it pertains to TAAA surgery.

Esmolol and landiolol, selective beta1-adrenoreceptor antagonists, provide neuroprotection against spinal cord ischemia and reperfusion in rats

BACKGROUND

Paraplegia is a devastating and unpredictable complication occasionally resulting from surgery of the thoracic and thoracoabdominal aorta. Because ultrashort-acting selective beta(1)-adrenoreceptor antagonists provide neuroprotective effects after brain ischemia, we hypothesized that they would also ameliorate spinal cord injury after transient ischemia and reperfusion in rats.

METHODS

Male Sprague-Dawley rats were randomly assigned to one of the following 4 groups: saline (received IV infusion of 0.9% saline at a rate of 0.5 mL/h, n = 8), esmolol (esmolol 200 microg/kg/min, n = 8), landiolol (landiolol 50 microg/kg/min), or sham surgical (n = 6). Infusion of saline or drugs was initiated 30 minutes before spinal cord ischemia and continued for the subsequent 24-hour reperfusion. Spinal cord ischemia was induced by intraaortic balloon occlusion combined with proximal arterial hypotension for 10 minutes. The spinal cord was then reperfused for 24 hours. Ischemic injury was assessed in terms of the motor deficit index score of the hindlimb and the number of viable motor nerve cells in the anterior spinal cord at 24 hours after reperfusion.

RESULTS

The motor deficit index scores were significantly lower in the esmolol and landiolol groups compared with the saline group (P < 0.05). Histopathologic evaluation of the spinal cord showed less damage in the esmolol and landiolol groups than in the saline group (P < 0.05).

CONCLUSIONS

These data show that ultrashort-acting selective beta(1)-adrenoreceptor antagonists can reduce neurological injury in a rat model of spinal cord ischemia-reperfusion.

[Anesthesiologic procedure for elective aortic surgery]

Aortic aneurysms are frequent in the elderly who often suffer from relevant co-morbidities. In Germany it is estimated that approximately 250,000 patients suffer from an aortic aneurysm. Due to the high risk of cardiac or pulmonary complications operative management poses a challenge to the anesthesiologist. Especially hemodynamic management during aortic cross-clamping requires anesthesiologic know-how and an anticipatory use of vasodilators and catecholamines. Furthermore, the anesthesiologist has to protect renal function. In order to avoid paraplegia due to spinal ischemia cerebrospinal fluid drainage may be necessary in patients with aneurysms of the thoracic aorta. In recent years endovascular repair of aortic aneurysms has been established in addition to conventional open surgery. As a consequence in some patients aortic surgery can be performed under regional or local anesthesia. In special cases thoracic endovascular repair requires a medicinal induction of heart arrest or the reduction of aortic blood flow by overpacing.