A new method of intrathecal PO2, PCO2, and pH measurements for continuous monitoring of spinal cord ischemia during thoracic aortic clamping in pigs

Background. Impaired spinal cord circulation during thoracic aortic clampin g may result in paraplegia. Reliable and fast responding methods for intrao perative monitoring are needed to facilitate the evaluation of protective m easures and efficiency of revascularization. Methods. In I I pigs, a multiparameter PO2, PCO2, and pH sensor (Paratrend 7, Biomedical Sensors Ltd, United Kingdom) was introduced into the intrathe cal space for continuous monitoring of cerebrospinal fluid (CSF) oxygenatio n, during thoracic aortic cross-clamping (AXC) distal to the left subclavia n artery. A laser-Doppler probe was inserted into the epidural space for si multaneous measurements of spinal cord flux. Registrations were made before and 30 minutes after clamping and 30 and GO minutes after declamping: The same measuring points were used for systemic hemodynamic and metabolic data acquisition. Results. The mean CSF PO2 readings of 41 mm Hg (5.5 kPa) at baseline decrea sed within 3 minutes to 5 mm Hg (0.7 kPa) during AXC (P < .01). Spinal cord flux measurement responded immediately in the same way to AXC. Both method s indicated normalization of circulation during declamping. Significant (P < .01) changes were also observed in the CSF metabolic parameters PCO2 and pH. Conclusions. In this experimental model of spinal ischemia by AXC, online m onitoring of intrathecal PO2, PCO2, and pH showed significant changes and c orrelated well with epidural laser-Doppler flowmetry (P < .01).