PREVENTION OF SPINAL-CORD DYSFUNCTION IN A NEW MODEL OF SPINAL-CORD ISCHEMIA

Paraplegia or paraparesis caused by temporary cross-clamping of the ao rta is a devastating sequela in patients after surgery of the thoracoa bdominal aorta. No effective clinical method is available to protect t he spinal cord from ischemic reperfusion injury. A small animal (rat) model of spinal cord ischemia is established to better understand the pathophysiological events and to evaluate potential treatments. Eighty -one male Sprague-Dawley rats weighing 300 g to 350 g were used for mo del development (45) and treatment evaluation (36). The heparinized an d anesthetized rat was supported by a respirator following tracheostom y. The thoracic aorta was cannulated via the left carotid artery for p ost-damping intra-aortic treatment solution administration. After thor acotomy, the aorta was freed and temporarily clamped just distal to th e left subclavian artery and just proximal to the diaphragm for differ ent time intervals: 0, 5, 10, 15, 20, 25, 30, 35 and 40 minutes (five animals per group). The motor function of the lower extremities postop eratively showed consistent impairment after 30 minutes clamping (5/5 rats were paralyzed), and this time interval was used for treatment ev aluation. For each treatment, six animals per group were used, and dir ect local intra-aortic infusion of physiologic solution (2 mL) at diff erent temperatures with or without buffer substances was given immedia tely after double crossclamp to protect the ischemic spinal cord. Arte rial blood (2 mL) was infused in the control group. The data indicate that the addition of HCO3-(20 mM) to the hypothermic (15 degrees C) so lution offered complete protection of the spinal cord from ischemic in jury. We conclude that this clinically applicable treatment warrants f urther investigation for the development of a ''neuroplegic solution'' for the protection of the ischemic spinal cord during repair of the t horacoabdominal aorta. Additionally, this report describes a technical ly easy and reproducible model of spinal cord ischemia suitable for ev aluating other therapies.