Postischemic hyperoxia enhances vulnerability in the rabbit spinal cord ischemic model

This study evaluated whether or not reperfusion of the rabbit ischemic spinal cord under conditions of varying blood oxygen tension combined with low blood viscosity can alter the neurological outcome after 15 min of infrarenal aortic occlusion. In group A (n = 20), hyperoxic reperfusion was performed during the initial 30 min of recirculation (pO2 = 460 ± 72 mmHg). In group B (n = 20), no attempt was made to manipulate the physiological arterial pO2 tension. In group C (n = 20), graded postischemic reoxygenation was applied during 15 min of recirculation beginning with 48 ± 12 mmHg as the initial arterial pO2. Neurological analysis revealed a high incidence of paraplegic animals after hyperoxic reperfusion as opposed to relatively undamaged animals after normoxic or graded postischemic reoxygenation. The possible role of different pathobiochemical events, specifically the high molecular oxygen availability and oxygen free-radical overproduction, is discussed below with attention to the interneuronal destructive process, detected during the early reoxygenation phase by means of the Nauta method permitting the visualization of the early signs of somatic and dendritic argyrophilia.