Abstract 303: Optic Nerve Sheath Diameter Differences by Sex, Rhythm, and Neurological Outcome After Out-of-hospital Cardiac Arrest

Introduction: Neurologically guided resuscitation after out-of-hospital cardiac arrest (OHCA) to improve survival has been limited due to knowledge gaps in cerebral edema changes. Point-of-care ultrasound (POCUS) for the assessment of optic nerve sheath diameter (ONSD) is an established modality to characterize the extent of cerebral edema. We aimed to describe ONSD differences by sex, rhythm type, neurological outcome using cerebral performance category (CPC), and overall survival status. Methods: We studied adult OHCA treated at an urban academic ED with return of spontaneous circulation (ROSC) from May 2018 to May 2020. After ROSC, trained emergency physicians obtained bilateral ONSD measurements at 1, 6, 24, 48, and 72 hours, in the transverse, oblique, and sagittal planes for each eye. All the ONSD measurements were averaged for each time point and comparisons were made between each predictor’s categories. To compare the mean at each time point between groups, t-test or ANOVA was used. The trend comparison was done using generalized estimating equations. Statistical analysis was performed using SAS 9.4 under the significance level of 0.05. Results: Out of 62 eligible patients, 35 (56%) were male and 27 (44%) were female, 33 (59%) had a shockable rhythm and 23 (41%) had non-shockable rhythm. At 72 hr, 6 (10%) had a CPC of 1-2 and 57 (90%) had CPC of 3-5. Overall, there were 37 (61%) survivors and 24 (39%) non-survivors. There was a notable sex difference in the mean ONSD across all time points between males and females (p = 0.031), with males showing higher ONSD, and between shockable and non-shockable (p= 0.035), with the shockable group having relatively lower ONSD. There is a statistically significant difference of mean ONSD between CPC 1-2 and CPC 3-5 groups at 6hr, 48hr, and at 72hr, with higher means in the CPC 3-5 group. Across all times, the trend line was statistically significant between non-survivors and survivors (p= 0.015), with non-survivors having higher ONSD. Conclusion: Males, patients with non-shockable rhythm, CPC 3-5 at 72 hr, and non-survivors had higher ONSD. Understanding cerebral edema dynamics during resuscitation will allow for future work to potentially tailor interventions to individual patient cerebral injury patterns.