Abstract 273: Alpha-Delta Ratio Peak Appears Early After Return of Spontaneous Circulation in the Continuous Electroencephalogram of Patients With Good Outcome After Cardiac Arrest
Introduction: Several studies have shown that the alpha-delta ratio (ADR) is associated with ischemic brain injury. Recently, an animal study has revealed that the ADR reaches the maximum point at 11 hours after ROSC, followed by downward curve (ADR peak) in the continuous EEG recordings of the rats with good outcome after cardiac arrest. We examined the existence of the early ADR peak after cardiac arrest in human. Methods: This is a prospective, observational study. Forty patients who survived out-of-hospital cardiac arrest underwent 33°C-targeted temperature management. We induced 33°C within 5 hours after ROSC and maintained for 24 hours, followed by 12 hours of rewarming period. All patients received sedative and paralytic agents until the restoration of normothermia. We started continuous EEG monitoring within 20 hours after ROSC until 72 hours after ROSC or mental recovery. We calculated alpha (8 - 13 Hz) and delta (0.5 - 4 Hz) frequency bands and computed ADR in the bifrontal channel (F3 - F4), bicentral channel (C3 - C4) and biparietal channel (P3 - P4). We did not remove artifact nor seizure events. Therefore, the whole continuous recordings were analyzed. Good neurologic outcome was defined as cerebral performance category 1 and 2 one month after ROSC. Results: Twenty-five patients showed poor outcome, while 15 patients showed good outcome. The figure is showing mean ADR ± SD change over time. The ADR reaches its highest amplitude 10 hours after ROSC and gradually decreases in the patients with good outcome regardless of the recording channel. However, the 10-hour ADR was not significantly different between the groups due to the large variances. Conclusions: Similar to the rats, the ADR peak appears early in the human patients with good outcome. However, due to the highly variable trend, application of ADR peak as a prognostic marker is limited. Regardless, the ADR implicates the crucial window of brain recovery time and remains an important subject requiring further study.