Spinal cord oxygenation during thoracic aortic clamping in pigs

Abstract: Despite a dramatic reduction in the mortality associated with thoracoabdominal aorticreplacement during the past 40 years, spinal cord ischaemia that results in paraplegia remainsa serious complication. Simple and reliable intraoperative monitoring techniques are neededto detect impending neurological deficit in time to prevent permanent damage. The presentthesis covers several aspects of the monitoring of cerebrospinal fluid oxygen tension inexperiments involving clamping of the thoracic aorta, using a new method.Epidural laser Doppler flowmetry was used to validate online cerebrospinal fluid (CSF)PO2, PCO2 and pH measurements by Paratrend® catheter during thoracic aortic clamping inpigs. A new experimental prolonged spinal cord ischaemia model was established by using apassive aorto-aortic shunt. Influence of segmental spinal cord perfusion and manipulation ofproximal aortic pressure on CSF oxygenation were studied in this model. Finally, intrathecalvariables were correlated with ultrastructural changes in the spinal cord.Intrathecal oxygen tension was strongly correlated with laser Doppler registrations. Theprolonged selective spinal cord ischaemia model offered stable central haemodynamics duringaortic occlusion. Monitoring of CSF oxygen tension allowed rapid detection of alterations inthe circulation to the spinal cord. The importance of proximal aortic pressure on maintenanceof spinal cord oxygenation during aortic occlusion was shown. Paratrend®-derivedmeasurements correlated with electron microscopic evaluation of spinal cord changes. Inconclusion, continuous CSF PO2, PCO2 and pH monitoring may provide new possibilities forthe detection and management of neurological deficit during thoracoabdominal aortic replacement.