Spinal cord protection in open- and endovascular thoracoabdominal aortic aneurysm repair: critical review of current concepts and future perspectives.

Unresolved for over half a century now since the beginning of aortic surgery spinal cord injury (SCI) remains the most devastating complication after extensive open and endovascular thoracoabdominal aortic aneurysm (TAA/A) repair. Over the past decade extensive research on spinal cord perfusion lead to a better understanding of previously unknown physiologic mechanisms involved in the suspension of the cord's arterial supply and the consecutive development of SCI underscoring the need for new concepts in treatment strategy and monitoring methods during and after TAA/A repair. Based on this knowledge, new treatment strategies in particular the staged-repair were developed. The first-in-man translation of this idea has just been published introducing the new concept: minimally invasive selective segmental artery coil-embolization. Another approach to overcome the most critical initial period after segmental artery occlusion due to stent graft deployment in the descending or thoracoabdominal aorta is temporary aneurysm sac perfusion, which also has recently been clinically trialed. Furthermore, the new non-invasive real-time monitoring method to record spinal cord viability by means of near-infrared spectroscopy of the paraspinal collateral network by means of near-infrared spectroscopy has also been suggested and successfully introduced in a pilot series to a clinical setting. This review addresses problems, unsolved questions and future perspectives regarding these three new concepts.

Spinal cord ischemia in open and endovascular thoracoabdominal aortic aneurysm repair: new concepts.

For more than half a century ischemic spinal cord injury (SCI) and consecutively permanent paraplegia remained the most devastating complication after open and endovascular thoracoabdominal aortic aneurysm (TAAA) repair. Various neuroprotective strategies (e.g., motor-/somatosensory evoked potential monitoring and cerebrospinal fluid drainage) used as adjuncts have lowered the SCI; maybe most importantly, the modern collateral network (CN) has begun to replace the classic understanding of spinal cord blood supply implying several consequences. Reliable non-invasive tools to monitor cord perfusion to detect imminent spinal cord malperfusion, ischemia and forthcoming neurologic injury (particularly early postoperatively) is not available, neither is a reliable strategy to prevent ischemic injury during distal circulatory arrest and after segmental artery occlusion. Currently, two promising new concepts--potentially advancing spinal protection in open and endovascular TAAA repair--address these issues: 1) non-invasive real-time monitoring of the paraspinous CN-oxygenation via near-infrared spectroscopy (NIRS) as an alternative to the demanding direct neuromonitoring; and 2) preconditioning of the CN as minimally invasive, endovascular "first stage" to increase the resilience of spinal cord perfusion prior to definite aortic repair. This article illustrates both concepts discussing: 1) the clinical application of thoracic and lumbar collateral NIRS monitoring to indirectly detect spinal cord hypoperfusion; and 2) minimally invasive selective segmental artery coil-embolization (MISACE) for (arteriogenic) preconditioning of the CN prior to extensive open or endovascular staged TAAA repair.

Near-infrared spectroscopy monitoring of the collateral network prior to, during, and after thoracoabdominal aortic repair: a pilot study.

OBJECTIVE: The aim of this study was to evaluate the feasibility of non-invasive monitoring of the paraspinous collateral network (CN) oxygenation prior to, during, and after thoracoabdominal aortic repair in a clinical series. METHODS: Near-infrared spectroscopy optodes were positioned bilaterally-over the thoracic and lumbar paraspinous vasculature-to transcutaneously monitor muscle oxygenation of the CN in 20 patients (age: 66 ± 10 years; men = 11) between September 2010 and April 2012; 15 had open thoracoabdominal aortic repair (Crawford II and III), three had thoracic endovascular aortic repair (TEVAR; Crawford I), and two had a hybrid repair (Crawford II). CN oxygenation was continuously recorded until 48 hours postoperatively. RESULTS: Hospital mortality was 5% (n = 1), 15% suffered ischemic spinal cord injury (SCI). Mean thoracic CN oxygenation saturation was 75.5 ± 8% prior to anesthesia (=baseline) without significant variations throughout the procedure (during non-pulsatile cooling on cardiopulmonary bypass and with aortic cross-clamping; range = 70.6-79.5%). Lumbar CN oxygenation (LbS) dropped significantly after proximal aortic cross-clamping to a minimum after 11.7 ± 4 minutes (74 ± 13% of baseline), but fully recovered after restoration of pulsatile flow to 98.5% of baseline. During TEVAR, stent-graft deployment did not significantly affect LbS. Three patients developed relevant SCI (paraplegia n = 1/paraparesis n = 2). In these patients LbS reduction after aortic cross-clamping was significantly lower compared with patients who did not experience SCI (p = .041). CONCLUSIONS: Non-invasive monitoring of CN oxygenation prior to, during, and after thoracoabdominal aortic repair is feasible. Lumbar CN oxygenation levels directly respond to compromise of aortic blood circulation.

Efficacy and frequency of cerebrospinal fluid drainage in operative management of thoracoabdominal aortic aneurysms.

BACKGROUND: Paraplegia remains the most dreaded complication following thoracoabdominal aortic repair. We investigated the efficacy of cerebrospinal fluid drainage as a spinal cord-protecting modality. We also evaluated the correlation between the frequency of cerebrospinal fluid drainage and the Crawford classification. METHODS: Spinal cord function was monitored during 20 open surgical procedures (group I) and 27 stent-graft implantations (group II). Evoked potentials and intracranial pressure were monitored in each operation. If intracranial pressure exceeded 15 mmHg, cerebrospinal fluid was drained. RESULTS: Cerebrospinal fluid drainage was necessary in 75 % of patients in group I (Crawford type I: 33 %, type II: 40 %, type III: 20 %, type IV: 7 %) and in 22 % of patients in group II (Crawford type I: 33 %, type II: 66 %). Evoked potential alterations correlated with an increase in intracranial pressure. Timely cerebrospinal fluid drainage reversed these changes in 72 %. Three patients remained paraplegic. CONCLUSION: Cerebrospinal fluid drainage is a valuable neuroprotective interventional tool to lower the risk of spinal cord ischemia. The combination of neurophysiological monitoring and cerebrospinal fluid drainage optimizes the prevention of paraplegia during aortic repair.

Development of a special balloon occlusion device to prevent adverse events in high-risk patients during open aortic surgery.

OBJECTIVE: To prevent clamp injury that may occur during aortic surgery, we aimed to develop a special balloon occlusion (BO) device to lower the thromboembolic risk in patients with severe atherosclerosis during aortic aneurysm repair. METHODS: The study comprised two test phases: a laboratory-testing series focussing on flexible artificial aortas, and an experimental series conducted on 10 pigs. RESULTS: The device proved to be effective during the laboratory tests and the experiments on pigs. No complications such as intraoperative balloon rupture, dislocation, or occlusion leaks occurred. No damage to the aortic vessels was observed in further histological examinations. CONCLUSIONS: This BO device has the potential to become an alternative to cross-clamping for vascular surgeons in patients with severely atherosclerotic vessels.