EPIDURAL PERFUSION COOLING PROTECTION AGAINST PROTRACTED SPINAL-CORD ISCHEMIA IN RABBITS

The protective effect of a modified epidural cooling technique was ass essed in a rabbit spinal cord ischemia model. The epidural space aroun d the lumbar segments with induced ischemia was continually perfused w ith cold (5-degrees-C) isotonic saline via two communicating spinal ca nal openings. This procedure allowed the spinal cord to be kept deeply hypothermic (< 15-degrees-C within central gray matter) during the is chemic period. The animals were subjected to either normothermic ische mia (Group A) or hypothermic ischemia (Group B). Each group contained three subgroups of animals undergoing 20, 40, or 60 minutes of aortic ligation. Their neurological outcomes were evaluated up to 48 hours po stischemia, and the intergroup differences were compared. Two days pos tischemia, all of the animals were sacrificed by transcardial perfusio n-fixation and their lumbar segments were processed for histopathologi cal examination. In addition, in animals with 60-minute ischemia, spin al somatosensory evoked potentials were recorded during surgical inter vention and again after 48 hours. In the normothermic animals, a high incidence of paraplegia was detected: in 40% after 20 minutes of ische mia, in 75% after 40 minutes, and in 100% after 60 minutes. In contras t, all of the hypothermic animals exhibited full neurological recovery even after 60 minutes of ischemia. Both electrophysiological and hist ological observations clearly correlated with the neurological finding s. The results suggest that deep spinal cord hypothermia produced by e pidural perfusion cooling provides effective protection against protra cted spinal cord ischemia in rabbits.