Hyperbaric oxygen therapy given 30 minutes after spinal cord ischemia attenuates selective motor neuron death in rabbits

Objective: Spinal cord ischemia sometimes causes paraplegia because the spinal motor neuron cells are vulnerable to ischemia. Although various protective remedies for spinal cord injury have been reported, there have been few established clinical methods. Although hyperbaric oxygen (HBO) has been used clinically as a treatment for ischemia, the reason for its effectiveness is still uncertain because sufficient experimental data are lacking. Design: Prospective, randomized, controlled study. Setting: Experimental animal research laboratory in a university research center. Subjects: Twenty-three Japanese white rabbits, weighing 2-3 kg. Interventions: A modified rabbit spinal cord ischemia model of infrarenal aortic occlusion for 15 mins was employed. Rabbits were randomly assigned to four groups; the rabbits in group A did not undergo ischemic insults (n = 5). The rabbits in groups B and C underwent ischemic insult for 15 mins, followed by 1 hr of HBO treatment at 3 atm absolute with 100% oxygen at 30 mins (n = 6) or 6 hrs (n = 7) after reperfusion, respectively. The rabbits in group D underwent ischemic insult for 15 mins without HBO treatment (n = 5). Measurements and Main Results: We observed neurologic functions for 14 days. The sections of the spinal cords were stained with hematoxylin and eosin, and the number of spinal motor neurons in ventral region was counted by light microscopy. All rabbits in groups A and B could stand, whereas all rabbits in groups C and D showed irreversible paraplegia on days 2 and 14 after reperfusion. Spinal motor neurons in ventral gray matter in groups C and D decreased significantly compared with those in groups A and B. Conclusions: HBO therapy shortly after ischemic insult had protective effects against ischemic spinal cord damage. However, delayed treatment with HBO did not change the prognosis.