Intraoperative spinal cord monitoring during descending thoracic and thoracoabdominal aneurysm surgery

doi:10.1016/S0003-4975(02)04137-1

The Annals of Thoracic Surgery

Volume 74, Issue 5, November 2002, Pages S1873-S1876

Presented at the Aortic Surgery Symposium VIII, May 2–3, 2002, New York, NY.

https://doi.org/10.1016/S0003-4975(02)04137-1 Get rights and content

Abstract

Background

Postoperative paraplegia is one of the most dreaded complications after descending thoracic and thoracoabdominal aneurysm surgery. In this study, intraoperative monitoring was applied during resection of descending thoracic and thoracoabdominal aneurysms to detect spinal cord ischemia and help prevent paraplegia.

Methods

Fifty-six patients (descending thoracic, 25; thoracoabdominal, 31) were monitored intraoperatively with both motor- (MEP) and somatosensory- (SSEP) evoked potentials. MEPs were elicited with transcranial electrical stimulation and recorded from the spinal epidural space (D wave) or peripheral muscles (myogenic MEP). SSEPs were obtained with median and tibial nerve stimulation.

Results

A total of 16 patients (28.6%) showed MEP evidence of spinal cord ischemia, only 4 of whom had delayed congruent SSEP changes. In 13 patients (23.2%), ischemic changes in MEPs were reversed by reimplanting segmental arteries or increasing blood flow or blood pressure. None of these 13 patients suffered acute paraplegia regardless of the status of SSEP at the end of the procedure, but 1 of them developed delayed postoperative paraplegia after multisystem failure. Three patients (5.4%) who had persistent loss of MEPs despite of recovery of SSEPs awoke paraplegic.

Conclusions

The results demonstrate that compared with SSEP, MEP, especially myogenic MEP, is more sensitive and specific in detection of spinal cord ischemia, and that intraoperative monitoring can indeed help prevent paraplegia.

Section snippets

Patients

Fifty-six consecutive patients (female, 26; male, 30; age, 29 to 78 years, mean 67 years) undergoing DTA (n = 25) or TAA (n = 31) repair between August 1996 and October 2001 were included in this study. Each patient had preoperative SSEP baseline studies and gave informed consent for TCES.

MEP recording

MEPs were elicited with TCES applied through spiral needle electrodes placed at C1 and C2 scalp sites (International 10 to 20 System) and recorded from the spinal epidural space (D wave, 16 patients) or

Results

Neurophysiological spinal cord monitoring, combined with other protective adjuncts (eg, retrograde aortic perfusion, CSF drainage, and moderate or deep hypothermia), was performed for 56 patients with DTA (n = 25) or TAA (n = 31) during repair of their aortic aneurysms. In this series of patients, in-hospital mortality was 5.4% (3 of 56 patients). The causes of death include cardiac (n = 1), respiratory (n = 1), and renal failure (n = 1).

Sixteen patients (28.6%) had significant MEP changes (

Comment

In this study, spinal cord function in 56 patients with descending aortic aneurysms was monitored intraoperatively with both SSEPs and MEPs. Sixteen patients had significant MEP changes, among which only 4 patients had delayed accompanying SSEP alteration. Loss of MEPs from the lower extremities suggested anterior cord ischemia and prompted intervention to restore blood supply to the spinal cord. Although 1 developed delayed postoperative paraplegia, all 13 patients with restoration of MEPs

Acknowledgements

We thank Karin Liddle, Nimira Bapoo, and Peter Van Rienen, IOM technologists at Vancouver General Hospital, for their dedicated technical support.

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Thoraco-abdominal aneurysm (TAA) repair carries a significant risk of spinal cord infarction. The latter results from irreversible changes in the spinal cord arterial network, e.g., sacrifice of the segmental arteries. Intra-operative neurophysiology with somatosensory and especially motor evoked potential (SEP and MEP respectively) monitoring, has emerged as an effective tool to assess the efficiency of the collateral blood flow, detect reversible spinal cord ischemia and guide the peri-operative multidisciplinary management to prevent postoperative paraplegia. The main roles of such monitoring include diagnosis of spinal cord vs peripheral limb ischemia, titration of mean arterial pressure during aortic clamping, the guidance of selective re-implantation of critical segmental arteries, and management of hemodynamics in the immediate postoperative period. In addition, manipulation of the aortic arch and proximal descending aorta, adds the risk of cerebral infarction from both low flow state and/or thromboembolic events. As such, EEG monitoring may be a useful add-on for either assessment of the efficiency of cerebral cooling as a neuroprotective method and/or for detection and treatment of reversible cerebral ischemia. This chapter presents the multimodality approach to open TAA monitoring as a versatile tool for the prevention of devastating postoperative neurologic deficits.
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The perioperative physician encounters spinal cord injury (SCI) in a variety of contexts. For example, spinal cord ischemia leading to postoperative paraplegia or paraparesis remains a major cause of morbidity and mortality after open and endovascular repair of descending thoracic and thoracoabdominal aortic aneurysms. Additionally, SCI after central neuraxial anesthesia remains a rare but devastating complication. Anesthesiologists must also be aware of the neurologic complications they may encounter after the surgical management of spinal deformities. Efforts aimed at the preservation of spinal cord function after acute SCI are focused on primary injury prevention. Once injury has occurred, treatment focus shifts to minimizing secondary mechanisms of injury. Ischemic injuries may be prevented, limited, or treated by strategies directed at improving spinal cord perfusion. The severity of mechanical injuries may be abated by surgical stabilization or decompression. Medical therapies aimed at limiting secondary mechanisms of injury, often referred to as neuroprotection strategies, can be instituted after the primary injury has occurred with the aim of preventing further cell death and functional disability. The anesthetic management of patients with existing or prior SCI requires a thorough understanding of the associated physiologic alterations, including neurogenic shock and autonomic dysreflexia.
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Original article: aortic surgery symposiumIntraoperative spinal cord monitoring during descending thoracic and thoracoabdominal aneurysm surgery

Abstract

Background

Methods

Results

Conclusions

Section snippets

Patients

MEP recording

Results

Comment

Acknowledgements

Semin Thorac Cardiovasc Surg

J Thorac Cardiovasc Surg

J Vasc Surg

New and future approaches for spinal cord protection

Semin Thorac Cardiovasc Surg

Original article: aortic surgery symposium
Intraoperative spinal cord monitoring during descending thoracic and thoracoabdominal aneurysm surgery