Intercostal Artery Reattachment Guided by Intraoperative Neurophysiologic Monitoring During Open Thoracoabdominal Aortic
Intraoperative neurophysiological monitoring (IOM) can promptly detect spinal cord ischemia (SCI) during thoracoabdominal aortic aneurysm (TAAA) repair. Early detection of SCI gives the team the opportunity to trigger interventions for maximizing spinal c
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Ubaldo Del Carro, Francesca Bianchi, Marco Cursi, and Heike Caravati
Spinal cord ischemia (SCI) is one of the most important complications during thoracoabdominal aortic aneurysm (TAAA) repair. In an effort to reduce this risk, over the last few years, operative strategies have evolved from the traditional clamp-and-sew technique with epidural cooling to one applying distal aortic perfusion with a variety of additional strategies to protect the spinal cord [1]. Among these strategies, intraoperative neuromonitoring (IOM) allows for a real-time assessment of spinal cord functional integrity and early detection of SCI, providing the team with the opportunity to promptly trigger interventions for maximizing spinal perfusion and potentially reverse spinal injury [2–4]. Type I to III TAAAs are often repaired with distal perfusion techniques and neuromonitoring, while the use of such adjuncts is irregularly applied in the repair of type IV TAAA [5–7]. Literature data support the use of U. Del Carro (*) Department of Neurology and INSPE, Vita-Salute University, San Raffaele Scientific Institute, Milan, Italy e-mail: [email protected] F. Bianchi · M. Cursi · H. Caravati Department of Neurology and INSPE, San Raffaele Scientific Institute, Milan, Italy e-mail: [email protected]; [email protected]; [email protected] © Springer Nature Switzerland AG 2019 Y. Tshomba et al. (eds.), Visceral Vessels and Aortic Repair, https://doi.org/10.1007/978-3-319-94761-7_26
IOM as a strategy to detect SCI and to guide hemodynamic optimization and/or reimplantation of intercostal arteries to prevent or treat SCI, providing a level B of evidence [8]. The neuromonitoring modalities used during TAAA surgery are the somatosensory evoked potentials (SSEPs) and the motor evoked potentials (MEPs) because their neural pathways pass through the spinal cord and their sensitivity to ischemia [9]. These techniques are safe, do not interfere with surgical procedures, or modify the clamping time. SSEPs provide information about the somatosensory pathway in the spinal dorsal columns. Furthermore, their peripheral response (i.e., popliteal potential) is useful to monitor the impending peripheral nerve injury and therefore differentiates SCI from peripheral ischemia. Nielsen and Kardel studied the peripheral nerve conduction during ischemia and found that sensory conduction velocity exhibits a temporospatial slowing along the ischemic nerve segment, determining that conduction time increases and amplitude decreases rectilinearly with the squared duration of ischemia and proportionally to segment length [10]. Because TAAA surgery is more likely to compromise blood flow in the anterior spinal artery territory, the presence of synapses in the anterior horn gray matter makes MEPs more sensitive than SSEPs in detecting SCI. Furthermore, MEP monitoring has a better 297
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correlation with motor outcome because it monitors the corticospinal tract [9]. However, SSEPs can provide a neurophysiologic “background” on which
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