Effects of oxygen insufflation during pilocarpine-induced status epilepticus on mortality, tissue damage and seizures

Purpose: This prospective, randomized study was performed to investigate the effects of oxygen (O₂) treatment during sustained epileptic activity on mortality, subsequent seizure frequency, and neuronal damage. Methods: Status epilepticus (SE) was induced by intraperitoneal injection of 340mg/kg pilocarpine, and terminated by diazepam after 40min. During SE, rats were randomized to O₂ treatment (insufflation rate of 1.5l/min O₂) during SE or normal air conditions. Outcome measures were SE-related mortality, seizure occurrence, mossy fiber sprouting, neuronal cell loss and expression of 27-kDa heat-shock protein (Hsp27). Results: O₂-treated and O₂-untreated animals did not differ with respect to SE latency, diazepam dose required to stop SE. While 7/38 rats died during SE in the O₂-untreated group, very little mortality (1/38) occurred in the O₂-treated group (P<0.05). However, within 1h after SE termination, seven O₂-treated rats died which was not observed in the O₂-untreated group indicating no significant difference in overall mortality. There was a tendency towards lower seizure rate in the O₂-treated group at one month after pilocarpine-induced SE. Three months after SE, however, seizure rates were no longer different between both groups. Moreover, mossy fiber sprouting, neuronal cell loss and Hsp27 expression did not differ between O₂-treated and O₂-untreated groups. Conclusion: Our findings indicate that O₂ treatment might delay the relative risk of epileptic seizures following an initial brain injury, but it may also lead to a rather unfavorably increased heterogeneity of epileptogenesis in experimental studies.