Time-dependent association of grey-white ratio on early brain CT predicting outcomes after cardiac arrest at hospital discharge.

Background: Cerebral edema after cardiac arrest can be quantified by the ratio of grey matter to white matter radiodensity (GWR) on computed tomography (CT). Severe edema predicts worse outcomes. We hypothesized the sensitivity and false positive rate of GWR predicting outcomes change over the first 24 hours post-arrest.

Methods: We performed a single-center retrospective cohort study including patients resuscitated from cardiac arrest between January 2010 and December 2023 who were unresponsive to verbal commands. We excluded patients who arrested from a primary traumatic or neurological etiology and those without brain imaging within 24 hours of arrest. We divided patients into groups based on time from arrest to CT, then quantified the performance of GWR dichotomized at <1.10 and <1.20, predicting in-hospital mortality and death by neurologic criteria (DNC).

Results: We included 2,204 patients with mean age 59 (SD 16) years. Overall, 1651 (75%) died in the hospital, of whom 248 (11%) progressed to DNC. Sensitivity of GWR <1.10 and GWR <1.20 for predicting in-hospital mortality increased over the first four hours post-arrest, reaching a maximum of 25% after five hours, while false positive rates remained <5% at all time points. Similar temporal trends were observed with DNC, although absolute values of sensitivity and false positive rate (FPR) varied.

Conclusion: The sensitivity and FPR of early GWR predicting in-hospital mortality and DNC after resuscitation from cardiac arrest varies over the initial post-arrest period. Reduced GWR on brain CTs is most sensitive for in-hospital mortality when obtained more than four hours post-arrest and for DNC when obtained between four and five hours. However, FPR remained execellent throughout, making early reductions in GWR a specific marker of poor outcome regardless of timing. While brain CTs obtained within the first 24 hours post-arrest may be indicated to evaluate for neurologic etiologies of arrest, they may be less informative as an independent marker of prognosis.