Management of thoracoabdominal aortic aneurysms and dissections : with emphasis on spinal cord protection in aneurysm repair and non-surgical treatment of type-B dissection
Abstract: Thoracoabdominal aortic aneurysms and dissections are two very serious disease processes which entail a high risk of vessel rupture and death. Their specific treatment strategies have several similarities which have formed a base for this thesis. Ever since its inception, surgery on the thoracoabdominal aorta has been associated with paraparesis and paraplegia. Surgical adjuncts, i.e. distal aortic perfusion and cerebrospinal fluid drainage have been developed to minimize neurological injury. For type B aortic dissection, surgery during the acute phase has been abandoned in favor of conservative treatment with rigorous blood-pressure management. Spinal complications after extended cross-clamping of the thoracoabdominal aorta were studied comparing simple cross-clamp technique and the use of surgical adjuncts. Distal aortic perfusion and cerebrospinal fluid drainage decreased the risk of prolonged cross-clamp time during thoracoabdominal aortic aneurysm repair, particularly for highest risk type II aneurysms. In a canine model the same adjuncts reduced the neurological injury after 60 min of occlusion of the descending thoracic aorta. Retrograde venous spinal cord perfusion did not prevent neurological injury. The usefulness of neurospecific proteins in cerebrospinal fluid (CSF) as markers of spinal cord injury during and after thoracoabdominal aortic aneurysm repair was evaluated. Multilevel somatosensory evoked potentials (SSEP) were measured intraoperatively. SSEP accurately detected spinal cord ischemia during surgery but did not identify all patients with a postoperativIy vulnerable spinal cord. The neurospecific proteins GFAp, NFL, NSE, and S100B increased in CSF with spinal cord injury but the increases became evident too late to change the surgical procedure. However, GFAp shows promise as a means of identifying patients with a vulnerable spinal cord and increased risk of delayed paraplegia. S100B increased in scrum from the surgical trauma alone without any parallel increase in CSF. Survival, aneurysm formation, and rate of rupture were prospectively studied and the quality of life surveyed during the chronic phase in patients given conservative treatment of acute type B aortic dissection. These patients have a survival and quality of life resembling that of the normal population. The relatively low rates of aneurysm formation and aortic rupture support the strategy of reserving surgical intervention to patients with complications of acute type B aortic dissection.
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