CLINICAL-APPLICATION OF EVOKED SPINAL-CORD POTENTIALS ELICITED BY DIRECT STIMULATION OF THE CORD DURING TEMPORARY OCCLUSION OF THE THORACICAORTA

Evoked spinal cord potentials elicited by direct stimulation of the co rd were used to monitor spinal cord ischemia in 68 patients undergoing temporary occlusion of the thoracic aorta (29 thoracic nondissecting aortic aneurysms, 9 nondissecting thoracoabdominal aneurysms, and 30 d issecting aneurysms). ''Immediate'' postoperative paraplegia developed in three patients and ''immediate'' paraparesis developed in one, whe reas ''delayed'' paraplegia developed in two others. During aortic cro ssclamping, four response patterns of the spinal cord potentials were obtained: (1) no change (n = 53), (2) change with return (n = 10), (3) change with inconsistent return (n = 2), and (4) change without retur n (n = 3). Neurologic complications occurred in 2%, 0%, 100%, and 100% of these groups, respectively. Delayed paraplegia developed on the se cond postoperative day in only one patient with a false-negative resul t, and the potentials correlated well with this patient's clinical neu rologic recovery. The aortic crossclamp time was significantly longer in the patients with ''change with inconsistent return'' and ''change without return'' than in the other two groups (p < 0.01). Femoral arte ry pressure and the cardiopulmonary bypass flow Fate were also signifi cantly lower in these groups than in the other two groups (p < 0.02 an d p < 0.01, respectively). We conclude that intraoperative monitoring of direct spinal cord responses is useful for the early detection of s pinal cord ischemia for assessing the efficacy of surgical countermeas ures.