Brief Altitude Exposure in New Zealand White Rabbits (Oryctolagus cuniculus) Does Not Produce Elevated Intracranial Pressure

Objective. Our intent was to observe the effect of simulated altitude exposure on the intracranial pressure (ICP) of New Zealand white rabbits. It is theorized that the hypoxia of high altitude causes a rise in ICP, which may play a role in the pathogenesis of acute mountain sickness (AMS). Dexamethasone is a medication used to treat AMS, but its mechanism of action in this disease is unknown. It is believed that dexamethasone may lower ICP and thereby relieve the symptoms of AMS, but to our knowledge no study has demonstrated the effect dexamethasone has on ICP during altitude exposure. Methods. We placed subdural ICP catheters in 10 rabbits and then placed the rabbits in an altitude chamber at simulated 5000m for 6 hours. Each rabbit was exposed to simulated altitude twice, once after several doses of dexamethasone and once after several doses of saline (placebo). We followed ICP measurements throughout the altitude chamber flights, comparing baseline with 6-hour ICP levels. Results. After 6 hours of altitude exposure, there was no significant change in the ICP of rabbits with either saline or dexamethasone administration. We were unable to replicate the altitude-induced rise in ICP observed in other animal studies. Conclusions. Intracranial pressure does not rise within the subdural space in rabbits during altitude exposures of 6 hours or less. Further, we are unable to draw conclusions regarding the mechanism of action of dexamethasone in the cerebral dynamics of AMS.