New surgical techniques for the prevention of paraplegia during aortic surgery.

It has been shown in previous publications that ischemic spinal cord injury after aortic cross-clamping may be produced by a steal-phenomenon. The present study investigates this phenomenon and the direction of spinal cord blood flow by directly measuring the oxygen tension on the spinal cord surface in pigs. After simple clamping of the aorta, oxygen tension decreased significantly distal to the clamping site both after occlusion of the thoracic aorta at T3-4 (group I) and the abdominal aorta at L1 (group II). Exclusion of the thoracic aorta by second clamping at T 13 restored oxygen tension almost to the control level while segmentation of the abdominal aorta up to S1 hardly affected oxygen tension in the area of the Adamkiewicz artery in most animals. An additional occlusion of the spinal cord proximal to the measuring point did not lead to a significant alteration of oxygen tension. It is concluded that, after aortic cross-clamping, blood tends to drain away from the spinal cord rather than supply it longitudinally. A steal phenomenon always has to be taken into account if any radicular artery, especially the artery of Adamkiewicz, supplies the spinal cord distal to the clamping. Without cognizance of the position of the Adamkiewicz artery in man as well as of the competence of the collateral circulation in the excluded segment, a new additional strategy needs to be developed for repair of the aorta. Two surgical techniques for the prevention of paraplegia after aortic cross-clamping are described and discussed: the counter occlusion technique and the bypass fractionated technique.