Abstract 313: Association Of Gray-White Matter Ratio With Severe Cerebral Edema In Comatose Cardiac Arrest Patients

Introduction: Previous studies have shown that lower gray:white matter ratio (GWR) is associated with poor outcomes in patients initially comatose after cardiac arrest. However, those studies focused on survival, a measure that may be confounded by withdrawal of life-sustaining therapy (WLST) decisions. We assessed the association of GWR with severe cerebral edema (SCE), a more objective imaging surrogate for neurologic injury. Methods: We retrospectively analyzed datasets acquired as part of a prospective observational study of 500 cardiac arrest patients with non-traumatic coma. Our analyses were limited to patients who underwent CT within 72 h of arrest, resulting in 151 patients. Some patients underwent repeat imaging, leading to a total of 175 imaging studies. Regions of interests (ROIs; 3x3) were drawn bilaterally in the caudate nuclei (CN) and posterior limbs of the internal capsule (PLIC) at the level of the basal ganglia on non-contrast axial CT scans. GWR was calculated as the ratio of mean x-ray attenuation in the CN to that in the PLIC. Scans whose radiology report described herniation or more than minimal ventricular effacement were classified as SCE. Poor outcome was defined as modified Rankin Scale Score > 4 at 6 months. Results: Patients with SCE were more likely to be younger (P<.0001), have a non-shockable rhythm (P=0.028), have a worse Glasgow Coma Scale (GCS) score on hospital admission (P=0.0047) and have a significantly lower GWR (P<.0001) compared to patients without SCE (see Table 1). Patients with SCE had a higher proportion of deaths at discharge due to brain death (P<0.0001). There was no significant difference in the proportion of patients with poor outcomes between the groups (P=0.13). Conclusion: For patients initially comatose after cardiac arrest, significant reductions in GWR are associated with SCE. Since this study utilized SCE as intermediate outcome measure for neurologic injury, these GWR results are not confounded by WLST decisions.