Relationship between cortical electrical responsiveness and changes in regional cerebral oxygenation (rSO2) and return of spontaneous circulation in prolonged cardiac arrest: a multi-center observational study.

BACKGROUND: Ischemic/anoxic brain injury is often assumed to occur within minutes of severe cerebral ischemia. However, emerging evidence suggests brain tissue may be more resilient, with important implications for resuscitation. We hypothesized that during prolonged cardiac arrest, cortical electrical activity may be restorable if cerebral oxygenation thresholds are met and may be associated with return of spontaneous circulation (ROSC).

METHODS: This was an ancillary cohort analysis of a multicenter, prospective observational study. Consecutive adult patients with in-hospital cardiac arrest were continuously monitored using electroencephalography (EEG) and near-infrared spectroscopy to assess regional cerebral oxygen saturation (rSO2) during cardiopulmonary resuscitation (CPR).

RESULTS: Among 85 cardiac arrests (median duration 31 min, IQR 23-45), 53 yielded interpretable EEG recordings. Diffuse cortical suppression was the most common pattern (47%), but near-normal rhythms (40%: delta 22%, theta 12%, alpha 6%) and pathologic activity (13%) appeared above specific rSO2 thresholds. Delta and theta emerged at rSO2 ≥16%, and alpha at >40%. Alpha activity was seen up to 35 min, and delta/theta up to 60 min into CPR. Suppression reverted to near-normal in 12% of transitions. Alpha activity was associated with ROSC (OR 5.4; 95% CI 1.08-29.20; p = 0.045), while suppression predicted lower ROSC odds (OR 0.12; 95% CI 0.02-0.53; p = 0.002). Survival analysis was limited by small sample size.

CONCLUSION: Near-physiologic brain activity may be restored during prolonged CPR if oxygenation thresholds are met and is associated with ROSC. Further research is needed to evaluate survival outcomes.