Systemic Hypothermia in the Acute Management of Traumatic Optic Neuropathy in a Murine Animal Model

Abstract

Purpose: To examine the effects of systemic hypothermia on retinal ganglion cell survival and visual outcomes after optic nerve trauma in a sonication-inducted traumatic optic neuropathy murine animal model. Methods: Twenty mice underwent sonication-inducted traumatic optic neuropathy. Afterward, 10 mice were placed on a warming pad set to 36°C, and 10 mice were placed on a table. General anesthesia was maintained for 3 hours with subcutaneous injections of ketamine. The rectal temperature was measured every 15 minutes. Pattern electroretinograms were obtained at 2, 4, and 6 weeks. Mice were sacrificed at 6 weeks, and retinal ganglion cell counts were performed. Results: The hypothermia group had an average rectal temperature of 23.1°C; the control group was 33.3°C. At 6 weeks, the hypothermia group had larger a-wave amplitudes (18.19 µV) than the control group (12.75 µV) (p < 0.05). At 6 weeks, retinal ganglion cell density over the entire retina was significantly higher in the hypothermia group versus the control (p < 0.0001). Conclusions: The hypothermia treatment group had significantly higher retinal ganglion cell density and pattern electroretinogram a-wave amplitudes 6 weeks after injury than the control group. Systemic hypothermia may have a neuroprotective effect when initiated immediately after sonication-inducted traumatic optic neuropathy.