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Clinical application of continuous intraoperative neuromonitoring and selective use of temporary femoral conduits to minimize lower extremity ischemia and risk of spinal cord injury during complex endovascular thoracic and thoracoabdominal aortic repair
Peter Banga, MD, Gustavo S. Oderich, MD, Eric Sorenson, MD, Leonardo Reis de Souza, MD, Josh Netcott, R. EEG. T, Jan Hofer, RN, Stephen Cha, MS, Peter Gloviczki MD, MD.
Mayo Clinic, Rochester, MN, USA.
Purpose: To review the clinical utility of intra-operative motor-evoked (MEP) and somatosensory-evoked potential (SSEP) monitoring with selective use of temporary femoral conduits (TFCs) in patients undergoing endovascular repair of descending thoracic (DTA) and thoracoabdominal aortic aneurysms (TAAAs).
Methods: We reviewed the clinical data of 49 patients (38 male; mean age of 75±8 years old) who underwent endovascular repair of DTA and TAAAs (2007-2014). Patients treated by fenestrated and branched endografts were enrolled in prospective physician-sponsored investigational device exemption protocols. Patients requiring extensive aortic coverage had cerebrospinal fluid (CSF) drainage, permissive hypertension and MEP/SSEP monitoring. TFCs were used in patients with difficult visceral artery anatomy, allowing withdrawal of the device sheath into the conduit while performing visceral stenting. Changes in MEP/SSEPs prompted maneuvers to optimize spinal cord perfusion and restore lower extremity (LE) blood flow whenever possible. End-points were spinal cord injury (SCI) and LE ischemic complications.
Results: 45 patients (92%) had TAAAs, 4 (8%) had DTAs. 163 visceral arteries were targeted by fenestrations and branches (mean, 3.7±0.1 vessels/patient). Temporary conduits were used in 12 patients/14 limbs (11 TFCs, 3 iliac). A stable MEP/SSEP was achieved in all patients. 29 patients (59%) had >75% decrease in MEP amplitude in 40 limbs. MEP changes started 76±29 minutes after vascular access and were more prominent in the side of the larger sheath. Patients with temporary conduits less often had MEP changes compared to those without conduits (21% vs 47% of limbs, P<0.01). MEP amplitude partially improved in 7 patients/ 9 limbs (23%) with intra-operative maneuvers to increase mean arterial pressure and lower CSF pressure. With restoration to LE blood flow, MEP/SSEPs returned to baseline in all except for one patient who developed immediate permanent paraplegia. A second patient developed delayed paraplegia after open repair of retrograde type A dissection 2 days after the initial procedure. There were no other SCIs or LE ischemic complications.
Conclusion: Neuromonitoring is a reliable technique to assess LE ischemia and spinal cord function and predicts immediate SCI during endovascular repair of complex aortic aneurysms. Temporary iliofemoral conduits allow immediate restoration of LE blood flow in difficult cases where prolonged LE ischemia is anticipated. Identification of MEP/SSEP changes allows institution of a standardized protocol to optimize spinal cord perfusion and restore LE blood flow.
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