Abstract 204: Optic Nerve Sheath Diameter Trajectories During Targeted Temperature Management

Introduction: The extent of hypoxic-ischemic injury (HII) after cardiac arrest (CA) remains an important knowledge deficit with lack of objective clinical data that is measurable repeatedly. There is a need to better understand an individual patient’s level of HII. Optic nerve sheath diameter (ONSD) has not been explored after CA as a possible bedside modality to measure the extent of HII over time, at the bedside, during targeted temperature management (TTM). Objective: We sought to characterize the temporal trajectories of point-of-care ultrasound obtained ONSD during the post- return of spontaneous circulation (ROSC) phase, in patients with and without TTM. Methods: Adult CA patients at an urban academic ED were included from 2017-2021. ONSD was measured by emergency ultrasound fellowship trained faculty at 1, 6, 24, 48, and 72 hours after ROSC using an ocular preset on a 15MHz linear probe. ONSD measurements at these time points were compared with patient demographic information and intervention of TTM . Results: A total of 78 participants had ONSD measurements. The mean age was 62 (+/-15) and 46% were female. Of the 65% of the cases with TTM, a sex disparity was noted with 73% of males receiving TTM versus 56% of females. There was a trend toward a decrease in mean ONSD by 0.015cm for TTM patients during the early time points of 1 to 6 hours compared to an increase in 0.006cm in those without TTM. Similar trend was noted between 1 to 24 hours, with a decrease in ONSD by 0.025cm in those with TTM relative to an average increase of 0.008 cm in those without TTM. However, neither delta ONSD was statistically significant between the two cohorts. When further assessing if delay in cooling had an impact on ONSD change, we found that the ONSD change between 24 to 48 hours was significantly increased in those in whom TTM was not initiated within 14 hours (beta=0.036; p=0.016). Conclusion: This pilot study revealed ONSD changes during TTM. There is potential for monitoring brain injury through ONSD trajectories to evaluate responders vs non-responders to TTM. Additional research is needed to evaluate ONSD changes during the rewarming time frame and may further distinguish patients with worse HII. Correlation to survival outcomes can be possible with a larger sample size.