An Experimental Study on the Changes of Rabbit EEG by Reoxygenation after the Exposure to Carbon Monoxide

ABSTRACT

BACKGROUND: Hyperbaric oxygen (HBO) therapy is applied for the treatments of various diseases inducing hypoxic states. However, reoxygenation of previously hypoxic tissue results in significant tissue damages through the mechanisms of oxygen toxicity. The authors investigated the characteristics of the EEG changes by hyperbaric oxygenation after the exposure to carbon monoxide, and the protective effects of allopurinol, an inhibitor of xanthine oxidase (XO), to the brain. METHODS: Sixty eight male rabbits of New Zealand white weighing 1,350-2,000 gm, were used. The rabbits were divided in 4 groups and measured EEG for 21 hours of experiments. RESULT: The delta waves were significantly increased and alpha waves significantly decreased, during CO exposure, HBO exposure only, and HBO exposure after CO exposure (P< 0.05 in all groups). The wave changes were most remarkable in CO-HBO group, and in this case the changes continued to the last period of the ambient air exposure stage. The brain injury did not decrease as appeared in EEG changes in rabbits treated with allopurinol. This result suggests that many other mechanisms might be involved in CO-HBO condition. The paroxysmal electrical discharges were mostly appeared during or after HBO exposure stages. CONCLUSION: The changes of EEG characteristic in hyperbaric oxygenation are the increase of delta wave and electrical paroxysmal discharges. There is no protective effect of allopurinol to the brain, which suggests that many other mechanisms other than XO might be involved.