Effect of delayed induction of postischemic hypothermia on spinal cord damage induced by transient ischemic insult in rabbits

Objective: This study was performed to determine the effect of delayed induction of mild hypothermia after transient spinal cord ischemia in rabbits. Methods: Abdominal aortic occlusion was performed for 15 minutes to induce spinal cord ischemia at a rectal temperature of 37.3±0.3°C. Four groups of rabbits were investigated: Group 1 (n=8) was subjected to ischemia and reperfused at the same temperature for 7 hours; Group 2 (n=8) was subjected to ischemia and reperfused at the same temperature for 1 hour, followed by 6 hours of systemic hypothermia (32.5±0.5°C); Group 3 (n=8) was subjected to ischemia, reperfusion at the same temperature for 3 hours and then 6 hours of systemic hypothermia (32.5±0.5°C); and Group 4 (n=8) comprised non-ischemic controls. Neurological status of all rabbits in Groups 1– 3 was recorded and animals were sacrificed 1 week after ischemic injury. Spinal cord sections were examined microscopically to determine the extent of ischemic neuronal damage. Results: Mean modified Tarlov’s score at 1 week after ischemic insult was 0.5±0.8 in Group 1, compared to 4.3±1.5 in Group 2 and 2.9±1.8 in Group 3. Mean total number of surviving neurons within examined sections of spinal cord was significantly greater for Groups 2 and 3 compared with Group 1 (Group 1, 81±66.1; Group 2, 293.4±110.9; Group 3,227.1± 105.5; p<0.001). Conclusions: Delayed postischemic hypothermia induced within 3 hours after reperfusion significantly reduces ischemia-induced spinal cord neuronal damage in rabbits.