Somatosensory evoked potentials in the detection of spinal cord ischemia in aortic coarctation repair

Cortical somatosensory evoked potential (SEP) monitoring was used in 15 patients 2 to 50 years old undergoing repair of aortic coarctation to detect the onset of spinal cord ischemia during the cross-clamp period. Three different response patterns were observed. In 8 patients (53%), the SEP remained unchanged throughout the cross-clamping. This was designated a type 1 response. Six patients (40%) showed a gradual deterioration in the SEP after 15 minutes of cross-clamping (type 2 response). All SEPs returned to normal levels within 5 minutes of release of the clamp. One patient (7%) demonstrated a decline in SEP commencing prior to the application of the cross-clamp when an intercostal vessel was controlled with slings. The SEP completely disappeared within 5 minutes of cross-clamping, but after 19 minutes the repair was completed and the SEP returned within 3 minutes of reperfusion (type 3 response). No patient sustained neurological sequelae of repair. We believe that SEP monitoring offers the potential to identify the patient at risk of developing spinal cord ischemia intraoperatively before irreversible damage occurs. However, it is susceptible to deep halothane anesthesia, which abolishes all cortical responses and requires expert monitoring.