Ischemic preconditioning reduces neurologic injury in a rat model of spinal cord ischemia

Background. Ischemic preconditioning (IPC) is an endogenous cellular protective mechanism whereby brief, noninjurious periods of ischemia render a tissue more resistant to a subsequent, more prolonged ischemic insult. We hypothesized that IPC of the spinal cord would reduce neurologic injury after experimental aortic occlusion in rats and that this improved neurologic benefit could be induced acutely after a short reperfusion interval separating the IPC and the ischemic insult. Methods. Forty male Sprague-Dawley rats under general anesthesia were randomly assigned to one of two groups. The IPC group (n = 20) had 3 minutes of aortic occlusion to induce spinal cord ischemia 30 minutes of reperfusion, and 12 minutes of ischemia, whereas the controls (n = 20) had only 12 minutes of isehemia. Neurologic function was evaluated 24 and 48 hours later. Some animals from these groups were perfusion-fixed for hematoxylin and eosin staining of the spinal cord for histologic evaluation. Results. Survival was significantly better at 48 hours in the IPC group. Sensory and motor neurologic function were significantly different between groups at 24 and 48 hours. Histologic evaluation at 48 hours showed severe neurologic damage in rats with poor neurologic test scores. Conclusions. Ischemic preconditioning reduces neurologic injury and improves survival in a rat model of spinal cord ischemia. The protective benefit of IPC is acutely invoked after a 30-minute reperfusion interval between the preconditioning and the ischemic event. (Ann Thorac Surg 1999;68:874-80) (C) 1999 by The Society of Thoracic Surgeons.