Regional lidocaine infusion reduces postischemic spinal cord injury in rabbits

Paraplegia secondary to spinal cord ischemia is a devastating complication in operations on the descending and thoracoabdominal aorta. We hypothesized that the tolerance of the spinal cord to an ischemic insult could be improved by means of regional administration of lidocaine. Thirty-one New Zealand white rabbits were anesthetized and spinal cord ischemia was induced by the placement of clamps both below the left renal vein and above the aortic bifurcation. The animals were divided into 5 groups. Aortic occlusion time was 20 minutes in Group 1 and 30 minutes in all other groups. Groups 1 and 2 functioned as controls. Lidocaine (Group 5) or normal saline solution (Group 3) was infused into the isolated aortic segment after cross-clamping. Group 4 animals received 20% mannitol regionally, before and after reperfusion. Postoperatively, rabbits were classified as either neurologically normal or injured (paralyzed or paretic). Among controls, 20 minutes of aortic occlusion did not produce any neurologic deficit (Group 1: 0/4 injured), while 30 minutes of occlusion resulted in more consistent injury (Group 2: 6/8 injured). Animals that received normal saline (Group 3) or mannitol (Group 4) regionally showed 80% neurologic injury (4/5). Animals treated with the regional lidocaine infusion (Group 5) showed much better neurologic outcomes (7/9 normal: 78%). This superiority of Group 5 over Groups 2, 3, and 4 was significant (P <0.02). We conclude that regional administration of lidocaine reduced neurologic injury secondary to spinal cord ischemia and reperfusion after aortic occlusion in the rabbit model.