Susceptibility of the injured rat brain to CNS oxygen toxicity

The possibility of an altered susceptibility of the injured brain to central nervous system (CNS) oxygen toxicity was examined in awake rats. Moderate to severe closed head injury with diffuse axonal damage was produced in anesthetized rats by the fluid percussion method (2-2.5 atm), after which chronic EEG electrodes were implanted. Twenty-four hours later, the rats were exposed to 5 atm abs (506.5 kPa) oxygen and the time to appearance of paroxysmal EEG patterns was noted. The difference between the 19 minute median latency of this group and 16 minute of a control group which underwent a sham operation did not reach statistical significance. Some injured animals convulsed with minimal or no EEG changes. The clinical implication could be that brain injured patients are not at higher risk of CNS oxygen toxicity but the EEG alterations that could potentially be used to forecast incipient convulsions, or be the indication of actual convulsions in the intact brain of a paralyzed patient, may not always be present.