New method for absolute spinal cord ischemia protection in rabbits

ObjectiveThis study aims to establish a superior procedure to prevent spinal cord damage after severe spinal cord ischemia during aortic surgery. We examined the synergistic effect of topical hypothermia of the spinal cord combined with radical scavenger infusion into the clamped segment of the aorta to prevent spinal cord damage in an animal model.MethodsSpinal cord ischemia was induced in rabbits by clamping the aorta between the renal artery and aortic bifurcation for 30 minutes. Rabbits were divided into four groups of 16 each: group I, sham-operated; group II, edaravone (6 mL, 4°C, 1 mg/kg); group III, saline (6 mL, 4°C) with transvertebral cooling pads; group IV, edaravone (6 mL, 4°C, 1 mg/kg) and transvertebral cooling pads. Solutions were injected into the clamped segment of the aorta. Postoperative assessments included the Tarlov score, spinal cord histopathology, and measurement of malondialdehyde levels in the spinal cord tissue.ResultsAt 48 hours after reperfusion, the mean Tarlov scores in groups I, II, III, and IV were 4.0, 1.5, 1.9, and 4.0, respectively. The mean number of normal motor neurons was significantly higher in groups I (54.1) and IV (53.7) than in groups II (32.8) and III (36.3; P < .001). The mean malondialdehyde level in groups I (19.8 nmol/mL) and IV (22.6 nmol/mL) was significantly lower than in groups II (64.8 nmol/mL) and III (60.9 nmol/mL; P < .001). At 168 hours after reperfusion, the mean Tarlov scores in groups I, II, III, and IV were 4.0, 1.1, 1.3, and 4.0, respectively. The mean number of normal motor neurons was significantly higher in groups I (52.9) and IV (50.8) than in groups II (22.4) and III (25.9; P < .001). The mean malondialdehyde level in groups I (20.7 nmol/mL) and IV (23.4 nmol/mL) was significantly lower than in groups II (68.9 nmol/mL) and III (61.6 nmol/mL; P < .001).ConclusionIn a rabbit model with aortic clamping up to 30 minutes, which consistently produces complete paraplegia in rabbits, spinal cord damage was partially reduced by topical cooling with transvertebral cooling pads or the injection of edaravone into the clamped segment of aorta, but was more effectively protected by a combined use of these two strategies.Clinical RelevanceSpinal cord injury after surgical repair of the thoracic or thoracoabdominal aorta is a disastrous complication. Cold blood infusion into the clamped segment of aorta during thoracoabdominal aortic aneurysm surgery has been used in human operations in our department to detect the presence of a critical Adamkiewicz artery. Edaravone might be used in the same manner, with additional protective effect against spinal cord ischemia-reperfusion injury. This study demonstrated the synergistic effect of topical hypothermia of the spinal cord combined with edaravone infusion into the clamped segment of aorta to prevent spinal cord damage after absolute spinal cord ischemia in an animal model. Further research is needed to investigate the applicability of this technique to clinical settings