[Prevention of spinal cord ischemia after thoracic aortic occlusion]

Paraplegia has been a devastating and unpredictable complication following surgical procedures necessitating temporary occlusion of the thoracic aorta. This study was undertaken to investigate the effect of the pressure gradient between the aortic pressure distal to the occlusion and cerebrospinal fluid pressure (CSFP), defined as "Relative spinal cord perfusion pressure" (RSPP) on the development of ischemia to the spinal cord by using somatosensory evoked potentials (SEP). In 30 mongrel dogs, the thoracic aorta just distal to the left subclavian artery was occluded for either 30 or 120 minutes until SEP disappeared. RSPP was maintained at 20, 30 or 40 mmHg in each dog by adjusting the degree of occlusion of th aorta and/or changing CSFP by withdrawal of cerebrospinal fluid or injection of normal saline into the subarachnoid space. SEP were recorded as a cortical response to the electrical stimulation of bilateral peroneal nerves. SEP did not disappear for 30 or 120 minutes when RSPP was 40 mmHg. It would be concluded that 40 mmHg or higher of RSPP is necessary in order to prevent the spinal cord ischemia due to the temporary occlusion of the thoracic aorta.