The Protective Effect Of Hyperbaric Oxygen Preconditioning,propofol And Ketamine On Spinal Cord Injury In Rabbits

Paraplegia is the most serious complication after thoracoabdominal aneurysm repeit The cause of acute spinal cord dysfunction is believed to be the result of spinal cord ischemia from hypoperfusion during aortic cross-clamping. Excitatory amino acid , accumulation of intracellular calcium and free radicals have been suggested to play important roles in neuroml injury after ischemi& Ho~ver, the preventive measures including hypothermia, NMDA receptor inhibitors, calcium channel blockers and free radical scavengers are unsatisfied ~th their clinical outcome. Therefore, a novel therapy to protect against spinal cord ischemic injury still needs to be further studied. The protection of hyperbaric oxygen (HBO) preconditioning and anesthetics on cerebral ischemia have been demonstrated elsewhere. Whether HBO preconditioning awl propofol can protect spinal cord from ischemic injury has not been demonstrated. The present study was undertaken to determine:(l)If the ischetnic tolerance could be induced in the spinal cord by repeated administration of HBO awl if HBO induced ischemic tolerance was mediated by oxygen free radicals produced by I-IBO; (2) To evaluate the effects of propofol and ketamine on the ischemic -3- spinal cord injuly in rabbits. PART 1: Objective The arm of this study was to determine whether the ischemic tolerance could be indtxed in the spinal cord by pretreatment with HBO and if HBO induced ischemic tolerance was mediated by oxygen free radicals generated by HBO. Methods There were two expenments in this ~mrt and totally 35 New Zealand white rabbits (2. L-2.3kg) were used in the study In Experiment 1, the Control Gmup(n~7) received no hyperbaric oxygen pretreatment before spinal cord ischemia. The I-IBO-l Group(n7) received HBO (2.5ATA, 1000/c 02, 1 h per day) pretreatment for 3 days and the HBO-2 Group (n~7) received HBO pretreatment for 5 days before ischemia. In Experiment 2, the HBO-3 Group (n~7) and HBO-4 Group (n~7) received HBO pretreatment for 5 days(2.5ATA, 1000/c 02,1 h per day) with the same protocol as that in Experiment 1 but the animals in HBO-3 and HBO-4 group were treated with saline and dinethylthiourea (DMTU 500mg/kg) respectively 1 h before each session of HBO. Lnfrarenal aorta clamping modal was used to induce spinal cord ischemia in this study Iscbemia lasted for 20 mm MAP~P~J~I)? heajt rate. Pa02 PaC02~ pH~. rectal temperature and plasma glucose were measured during experiment Malondialdehyde(MDA) level of serum were measured in Experiment 2.48 h after reperfusion, hindlimb motor fimction and histopathology of the spinal cord were examined. Results In Experment I, the neurologic outcome both in HBO-1 and HBO-2 Groups were better than that of Control Group (P<0.05). The neurologic outcome in HBO-2 was better than that of IIBO-1 Group (P<0.05). The normal neurons in the anterior spinal cord of HBO-2 Group were more than that of Control and HBO-l Groups. In Experiment 2, the neurologic and histopathologic outcome in HBO-3 Group were better than that of the Control Group and HBO4 group (P<0.0S). There was no significant difference in MDA production between the two groups. -4- Condusion: Hypeibeiic oxygen preconditioning could induce ischemic tolerance on spinal cord in rabbits. Five-day serial of HBO lrecondinoning induces stronger ischemic tolerance than t...