Response of spinal cord blood flow and motor and sensory evoked potentials to aortic ligation. To produce spinal cord ischemia in the lamb, ligation of the thoracic aorta was performed for 15, 30, and 45 minutes in three animals each. Spinal cord blood flow and motor and sensory evoked potentials were measured before, during, and after aortic ligation. Ischemia with a blood flow of zero during ligation was encountered in the thoracic and lumbar cords, followed by hyperemia upon release of the ligature. Both somatosensory and motor evoked potentials were obliterated during aortic ligation and gradually recovered following resumption of flow. Motor and sensory evoked potentials behaved similarly to high aortic ligation. 