Relationship between intrathecal oxygen tension and ultrastructural changes in the spinal cord during experimental aortic clamping

Objectives: to investigate spinal cord ultrastructure related to cerebrospi nal fluid (CSF) oxygenation. Design: experimental aortic occlusion model with intrathecal oxygen tension monitoring. Materials and methods: two groups of pigs underwent proximal (P) or double (D) aortic occlusion for 30 min followed by 1 h of reperfusion. In a third group (I) segmental arteries distal to T3 were clamped for 90 min. A thin p O(2), pCO(2) and pH sensor was placed intrathecally for continuous monitori ng of CSF. Spinal cord segments were studied by electron microscopy (EM). Results: in group P, CSF-pO(2) rapidly decreased during clamping and major changes in pH and pCO(2) were seen. EM demonstrated neuronal degeneration w ith loss of cellular integrity and severe affection of organelles. In the g roup D, CSF oxygenation decreased to about half, but with only moderate cha nges in the metabolic parameters. Group I showed no significant changes in CSF measurements. The latter groups were similar at EM, showing only mild m itochondrial changes. Conclusions: the level of CSF oxygenation during aortic cross-clamping or s egmental artery interruption seems to correlate with ultrastructural change s in the spinal cord. This online intrathecal monitoring technique may prov ide valuable information on spinal cord circulation during thoracoabdominal aortic surgery.