Regional Cerebral Oxygen Saturation as an Adjunctive Tool for Termination-of-Resuscitation Decisions in Out-of-Hospital Cardiac Arrest: A Prospective Observational Study

Background Widely accepted in-hospital termination-of-resuscitation (TOR) rules are currently lacking, and existing approaches do not incorporate real-time physiological monitoring. Regional cerebral oxygen saturation (rSO 2 ) has been associated with return of spontaneous circulation (ROSC) during cardiopulmonary resuscitation (CPR), but its role in TOR assessment remains unclear. Methods In this prospective observational study, adult patients with out-of-hospital cardiac arrest who underwent resuscitation with cerebral oximetry monitoring in the emergency department were enrolled. The primary objective was to identify low rSO 2 thresholds associated with failure to achieve ROSC. Futility-based threshold analyses were performed, with an emphasis on specificity for predicting non-ROSC cases and the corresponding residual risk of ROSC. Results Of 408 screened patients, 145 were included and 59 (40.9%) achieved ROSC. No patient achieved ROSC when cumulative peak rSO 2 remained <46% on the left side (0/23) or <47% on the right side (0/29) within the first 30 minutes of CPR. The corresponding observed specificity for non-ROSC was 100% in this cohort, although the exact 95% confidence intervals for residual ROSC risk were 0.0–14.8% and 0.0–11.9%, respectively. Conclusion Low cumulative peak rSO 2 thresholds identified subgroups with no observed ROSC and high specificity for non-ROSC in this cohort. Cerebral oximetry may provide adjunctive, prospectively observable physiological information for TOR-oriented assessment during resuscitation, although these thresholds are exploratory and require external validation.