Is @entity451 after repair of @entity1498 due principally to XXXX during aortic cross-clamping?

@entity1 @entity6997 @entity16 @entity1498 @entity439 @entity451 @entity551
The hypothesis is presented that @entity451 after @entity1498 is principally due to @entity551 of sufficient severity and duration. In a group of 103 @entity1 who underwent surgery during a 10-year period, the distal aortic pressure was maintained above 60 mm Hg while the aorta was cross-clamped or the period of cross-clamping was limited to less than 20 minutes. No @entity16 occurred. In 17 of the 103 cases aortic pressure decreased below 60 mm Hg, occurring in 8% of @entity1 with the aorta occluded below the left subclavian artery but in 30% of those occluded above. Therapeutic measures used in the 17 @entity1 included infusion of @entity6997 in five and limiting cross-clamp time to less than 20 minutes in 11. The theory is proposed that ligation of intercostal arteries in a @entity1 with @entity1498 cannot injure the spinal cord because the normal direction of blood flow is reversed. Certainly, in @entity1 without a @entity1498 , such as @entity439 , ligation of a critical intercostal artery may injure the spinal cord. However, in @entity1 with @entity1498 the direction of blood flow is reversed, blood flowing from the intercostals into the distal aorta. The vague relationship long noted between development of collateral circulation, including rib notching, and the frequency of @entity451 probably depends not on the presence of enlarged intercostal arteries but on whether their temporary occlusion at the time of aortic cross-clamping results in @entity551 . Data with somatosensory-evoked potentials measured during operations on the thoracic aorta in 25 @entity1 found no changes in sensory potentials as long as the distal aortic pressure remained above 60 mm Hg, but a gradual disappearance was found at lower pressures. In five of six @entity1 with large thoracicoabdominal @entity439 in whom sensory potentials were absent for longer than 30 minutes, @entity451 resulted. Use of somatosensory potentials provides a significant method for evaluating methods to protect from @entity451 . This method should be far more productive than are simple clinical experiences because the fortunate rare occurrence of @entity451 , one in 200, greatly limits available data.
