Effects of drug volume on the model for regional drug protection against spinal cord ischemiareperfusion injury in rabbits

Objective To compare the effects of different drug volume on the model for regional aorta-infused drug protection against spinal cord ischemia-reperfusion injury in rabbits.Methods Spinal cord ischemia model was induced in New Zealand white rabbits by infrarenal abdominal aorta occlusion with a balloon catheter for 30 min.Another polycarbonate catheter was inserted into the abdominal aorta with the tip close to the site of occlusion via the femoral artery.During the ischemic period,nothing (V0 group) or different volume (1.5,3.0 or 6.0 ml/kg) of normal saline containing methylene blue (V1.5,V3 and V6 groups) was consecutively infused into the occluded aortic segments via the polycarbonate catheter at different rate of 3.0,6.0,or 12.0 ml/(kg·h).The bilateral common iliac arteries were clamped simultaneouly to prevent drug solution leakage.Thirty min later,blood flow was regained for reperfusion.The change of mean aortic pressure distal to the occluded site was measured throughout the operation.Neurological function was assessed according to the modified Tarlov scales at the moment of palinesthesia and 6,24 and 48 h after reperfusion.Lumbar segements of the spinal cord (L4-5) were harvested at 48 h after reperfusion for histopathologic evaluation,and the total number of normal motor neurons in the anterior horn was counted.Results The abdominal aorta was not completely occluded in V6 group.In V3 and V6 groups,the distal aortic pressure during ischemia was higher than in V0 and V1.5 groups with (41.0 ± 5.5) and (49.4 ± 4.5) vs.(17.9±2.6) and (22.5±1.7) mmHg [1 mmHg=0.133kPa,P＜0.05],while the difference value between ischemia and the first 10 min of reperfusion was lower than in V0 and V1.5 groups with (44.9±8.9)and (32.3±9.4) vs.(62.5±6.3) and (61.8±4.5) mmHg (P＜0.05).Tarlovscores were higher in V6 group than in V0 group at all intervals (P ＜ 0.05).The number of normal motor neurons was greater in V6 group than in V0 group with 10 (5.0-12.0) vs.0 (0-4.5) (P＜0.05).There was no significant difference between other groups and V0 group (P ＞ 0.05).Conclusion Drug volume lower than 3 ml/kg can ensure the model stability of spinal cord injury when infused into the occluded aortic segments during the ischemic period.The optimal volume was 1.5 ml/kg. Key words: Spinal cord ischemia;  Reperfusion injury;  Arterial infusions;  Models,animal