Spinal Cord Protection for Descending or Thoracoabdominal Aortic Aneurysm Repair

Abstract

The mortality and morbidity of extensive thoracoabdominal aorta replacement has improved markedly in recent years [1]. However, postoperative paraplegia from spinal cord infarction remains the most devastating complication that faces patients undergoing surgery on the thoracoabdominal aorta because loss of lowerlimb function imposes severe constraints on the quality of life. Additionally, paraplegia is associated with higher postoperative mortality and morbidity. Despite advances in spinal cord protection, the risk of spinal cord ischemia or infarction as a consequence of open surgical repair of thoracoabdominal aortic aneurysms (TAAAs) remains within the range of 8-28%[2,3]. The registry of the Japanese Association for Thoracic Surgery reported that the hospital mortality for surgery on the thoracoabdominal aorta was 14.2% in 561 patients during 2008 [4]. The U.S. multicenter registry in 2001 disclosed that early mortality after thoracoabdominal aortic surgery was 20% [5]. There are two major events during which injury to the spinal cord can occur. Firstly, spinal cord injury happens depending on the duration and degree of ischemia during crossclamping. The surgeon must temporarily interrupt aortic blood flow to the lower body, which renders the distal organs (including the spinal cord) ischemic, in order to resect the aneurysm. Secondly, damage may occur from the loss of blood flow to the spinal cord after the period of aortic cross-clamping because of failure to reattach the intercostal and lumbar arteries that are critical to the spinal cord blood supply. Essentially, being a neural tissue, the spinal cord tolerates ischemia poorly and if infarction ensues, paraplegia results. A number of adjunctive measures have been used successfully to counteract the consequences brought about by spinal cord ischemia during surgical intervention and a precarious spinal cord blood supply postoperatively. The incidence of paraplegia and paraparesis at centers for aneurysm repair has been decreasing then. Occasionally, a case of spinal cord injury still occurs, and the most important factors for the prevention of either immediate or delayed paraplegia remain to be elucidated [6-10]. In this chapter, we review the contemporary anatomical and pathophysiological understanding of spinal cord blood supply and present the scientific basis for clinical interventions used during descending and thoracoabdominal aortic surgery in order to reduce the incidence of paraplegia.