Influence of anesthesia protocol in experimental traumatic brain injury

Most pharmacologic studies on brain trauma in animals are performed while t he animals are under general anesthesia, which can interfere with brain met abolism and modify the experimental results. This study investigates the ef fects of three anesthetic drugs (halothane 2% and 4%, propofol at 10 mg/kg, and chloral hydrate at 400 mg/kg) on the traumatic brain injury-induced ne urologic deficit in mice. Trauma was induced with a weight-drop device. For each drug, animals were divided into four groups; the first did not receiv e either anesthesia or trauma, the second received anesthesia but no trauma , the third received a trauma without anesthesia, and the fourth received a nesthesia before the trauma. A neurologic examination using two different s corings (string and grip test) was performed 1 hour and 24 hours after the trauma. Mortality after trauma was increased for halothane 4% (48% versus 2 0% in unanesthetized mice), propofol (80% versus 30%), and chloral hydrate (70% versus 44%). Halothane 2% did not increase the mortality in traumatize d mice. Halothane 2% or 4% anesthesia did not modify the string score after the trauma, Grip score after the trauma was better in mice anesthetized wi th halothane at either 2% or 4%. Mice injured under anesthesia with chloral hydrate had worse grip and string scores (P < .05) than unanesthetized mic e. These results lead us to question the influence of anesthesia on the res ults obtained in experimental neurophamacologic studies, particularly when there are discrepancies between two studies on the same pharmacologic treat ment, which differ in their anesthesia protocols.