Hyperbaric oxygen therapy accelerates neurologic recovery after 15-minute complete global cerebral ischemia in dogs

Although hyperbaric oxygen therapy is clinically used for the treatment of several types of ischemic brain injury, few basic animal studies are available that provide a rationale for this therapy for complete global brain ischemia. Therefore, we investigated the effect of hyperbaric oxygen therapy on neurologic recovery after 15-min complete global cerebral ischemia in a canine model. Complete global ischemia was induced in 19 dogs by occlusion of the ascending aorta and the caval veins. Nine dogs were randomized to treatment with hyperbaric oxygenation (3 atmospheres absolute, 100% oxygen for 1 hr) at 3, 24, and 29 hrs after ischemia under spontaneous respiration, while the other ten dogs served as the control group without hyperbaric oxygen therapy (group C). Neurologic recovery was evaluated based on the electroencephalogram (EEG) activity score (1 = normal; 5 = isoelectric) and the neurologic recovery score (100 = normal; 0 = brain death) over a 14-day postischemic period.

The survival rates were 3/10 (30%) in the control group vs. 7/9 (78%) in the group treated with hyperbaric oxygen (p < .05). Over the 14-day postischemic period, the best (lowest) EEG scores of each dog were significantly (1.7 +/- 0.2 vs. 2.9 +/- 0.3; mean +/- SE, p < .01) lower in the hyperbaric oxygen-treated group. The best neurologic recovery scores of each dog were significantly (69 +/- 6 vs. 48 +/- 5; mean +/- SE, p < .05) higher in the treated animals. The number of dogs that recovered to a neurologic recovery score of > 65 (assessed as a slight disability) were 1/10 in the control group and 6/9 in the group treated with hyperbaric oxygen (p < .02).

Hyperbaric oxygen therapy performed in the early postischemic period accelerated neurologic recovery and improved the survival rate in dogs after 15-mins of complete global cerebral ischemia.