Influence of low proximal aortic pressure on spinal cord oxygenation in experimental thoracic aortic occlusion

Background To evaluate the effect of low proximal aortic pressure on cerebr ospinal fluid (CSF) oxygenation in an experimental thoracic occlusion model . Methods. In nine pigs, continuous intrathecal pO(2), pCO(2) and pH monitori ng was used during double descending thoracic aortic clamping following ins ertion of an aorto-aortic shunt. In five pigs, the shunt was connected to a citrated bag adjusted at approximately 40-45 cm above the heart for partia l exsanguination in order to decrease mean proximal aortic pressure (MPAP) to below 50 mmHg. In four animals, sodium nitroprusside infusion was used f or this purpose, Results, Intrathecal pO(2) demonstrated a significant decrease from 4.9 +/- 2,1 to 2.9 +/- 2.4 kPa after 10 minutes of aortic cross-clamping. Lowering proximal aortic pressure caused a further significant decrease to 1.2 +/- 1.7 kPa (p < 0.05), In seven pigs (5 in the exsanguination and 2 in the vas odilator group), restoration of mean proximal aortic pressure to 94.0 <plus /minus> 27.7 caused a recovery of CSF pO(2) from 1.2 +/- 1.9 to 2.8 +/- 3.0 (p = 0.05). Conclusions. The results of this study demonstrate that MPAP which provides spinal cord perfusion through subclavian-vertebral arteries are crucial fo r maintenance of spinal cord oxygenation during thoracic aortic occlusion i n this pig model.