Intraoperative management of thoracic aortic aneurysm. Experimental evaluation of perfusion cooling of the spinal cord.

The early recognition and reversal of ischemic spinal cord injury have not been successfully accomplished during the conduct of surgical procedures requiring temporary occlusion of the thoracic aorta. Using a model of spinal cord infarction, we evaluated (1) a technique of perfusion cooling of the spinal cord designed to protect against the development of perioperative ischemic injury and (2) the utility of somatosensory cortical evoked potentials (SCEP) elicited by peripheral nerve stimulation in the detection of spinal cord dysfunction during normothermic and hypothermic ischemia. Six dogs (Group I) subjected to proximal and distal occlusion of the thoracic aorta for a 30 minute period at normothermia uniformly-sustained complete neurologic lesions confirmed by functional and histologic assessment. In a second group of six animals (Group II) likewise subjected to 30 minutes of aortic occlusion, regional cooling of the spinal cord was accomplished by perfusion of the thoracic intercostal arteries in the isolated aortic segment with an asanguineous hypothermic solution. The latter intervention substantially protected against the development of irreversible spinal cord injury; only one animal in this group had temporary postoperative paraparesis, and all animals had only minor abnormalities on histologic examination of the spinal cords (Group I versus Group II, p