Acute etomidate treatment reduces cognitive deficits and histopathology in rats with traumatic brain injury

Objective: To test the hypothesis that etomidate treatment improves functional, cognitive, and histologic outcome after experimental traumatic brain injury. Design: Controlled animal study. Setting: University research laboratory. Subjects: Male Sprague-Dawley rats. Interventions: Traumatic brain injury was produced by controlled cortical impact injury (4 m/sec, 2.6 mm of tissue deformation). Etomidate (2 mg/kg) was administered intravenously immediately before injury (n = 13) or 5 mins after injury (n = 12). Additional rats received saline treatment 5 mins after injury (n 12) or served as sham controls (n = 10). Measurements and Main Results. Rats were evaluated on beam balance and beam walk tasks on postoperative days 1-5 and then trained in the Morris water maze on postoperative days 14-18. On day 28, the rats were killed, and hippocampal CA(1) and CA(3) neuron counts and cortical lesion volume were measured in histologic brain sections. Preinjury etomidate attenuated beam balance deficits, water maze deficits, hippocampal CA(3) neuronal loss, and cortical tissue loss but did not attenuate beam walk deficits or hippocampal CA, neuronal loss. Postinjury etomidate attenuated water maze deficits, but it did not affect any other outcome measure. Conclusions. Administration of etomidate both before and after injury attenuates secondary injury resulting from traumatic brain injury, but the effect is more pronounced with pretreatment. The ineffectiveness of postinjury etomidate on motor and histologic tasks suggests a brief therapeutic treatment window in rats. However, the treatment window in humans is unknown. Lastly, postinjury etomidate did not exacerbate neurologic or histologic outcome.