Postconditioning, a series of brief interruptions of early reperfusion, prevents neurologic injury after spinal cord ischemia

OBJECTIVE: We sought to test whether postconditioning, a series of brief mechanical interruptions of reperfusion applied during the onset of reperfusion, can prevent neurologic injury of the spinal cord after transient ischemia. SUMMARY BACKGROUND DATA: Ischemia-reperfusion injury of the spinal cord is the principal mechanism leading to the paraplegia after surgery for descending and thoracoabdominal aortic aneurysms. Postconditioning has recently been demonstrated to confer cardioprotection by attenuating reperfusion injury. METHODS: Spinal cord ischemia was induced in rabbits by infrarenal aorta occlusion for 25 minutes. Control animals underwent no additional intervention. Two groups of animals underwent postconditioning consisting of 4 or 6 cycles of 1-minute occlusion/1-minute reperfusion, respectively, which were applied 1 minute after the start of reperfusion. In 2 additional groups, 6 cycles of postconditioning started 5 or 10 minutes after the onset of reperfusion, respectively. Hind-limb motor function was assessed during a 10-day recovery period using the modified Tarlov criteria. Histologic examination of the spinal cord was performed, and the number of intact motor neurons was counted. RESULTS: Compared with controls, 4 cycles of postconditioning significantly increased the Tarlov score and the number of intact motor neurons. Six cycles of postconditioning did not further improve the neuroprotection. Postconditioning starting 5 minutes after reperfusion still resulted in powerful neuroprotection, but the neuroprotection disappeared completely when postconditioning was delayed for 10 minutes. CONCLUSIONS: Postconditioning prevents neurologic injury of the spinal cord after ischemia, and the first few minutes of reperfusion are crucial to neuroprotection by postconditioning.