Computerized Tomography vs Ultrasound Imaging for Detecting Hypoxic-Ischemic Brain Injury

Introduction: After an out-of-hospital cardiac arrest (OHCA), the resulting hypoxic-ischemic injury (HII) to the brain remains the main cause of mortality. Standardized approaches for measuring the extent of injury and monitoring of changes are lacking and continue to be a critical barrier to progress in improving neurological survival. Objective: We sought to characterize the prevalence of HII detected on computerized tomography of the brain and its correlation to point-of-care optic nerve sheath diameter (ONSD) measurements as an alternative modality for detecting brain injury. Methods: Adult OHCA patients at an urban academic ED were included in this study on a convenience sample basis from 2018-2019. The patients were grouped by findings of hypoxic-ischemic injury (HII) on both initial and subsequent CT brain imaging performed after ROSC in respective groups. CT Brain findings were compared to ONSD measurements as performed with point-of-care ultrasound by fellowship-trained emergency physicians within one hour of hospital arrival and at 6 hours, after return of spontaneous circulation (ROSC) and to cerebral performance category (CPC) at hospital discharge. Results: 76 patients enrolled in the study had a median age was 59, 49% were female, and 37% survived to hospital discharge. 58 patients had CT head performed, 40 had ONSD measured within one hour, and 27 patients had both. Of that 27, 9 (33%) had evidence of HII on initial imaging and 15 (55%) had evidence of HII on subsequent imaging for a total of 20 unique patients. The average ONSD within 1 hour of ROSC for those with no HII on any imaging was 0.59 cm, and for those without HII on initial imaging but with HII on subsequent imaging was 0.67 cm, and this difference was statistically significant (p< 0.05). Of the 20 patients with HI, 14 (70%) patients died and 6 (30%) survived with a CPC of 4. The average time to first CT head was 4 hours and 45 mins and the average time to subsequent imaging was 97 hours and 45 mins. Conclusion: After an OHCA, early time point ONSD measurements can potentially indicate brain injury within 1 hour of ROSC even in those without initial evidence of HII on CT imaging.