Pre-hospital neurological risk stratification at return of spontaneous circulation (ROSC) after out-of-hospital cardiac arrest – the Pre-MIRACLE₂ score

Background: Out-of-hospital cardiac arrest (OHCA) remains a global health burden where neurological injury sustained is a key predictor of mortality but there are challenges in early risk stratification. This study aims to derive the Pre-MIRACLE₂ score, which excludes pH as a component from the MIRACLE₂ score, as a means of stratifying neurological risk in a pre-hospital setting. Methods: To validate the Pre-MIRACLE₂ score, we used (i) the EUCAR Registry retrospectively analysed from 1 May 2012 to 31 December 2021, and (ii) the GLOBAL-MIRACLE Registry, a prospective cohort analysed from 1 January 2022 to 31 May 2023. The primary outcome was poor neurological outcome (defined as Cerebral Performance Category 3–5) at hospital discharge. Results: From 1 May 2012 until 31 May 2023, 2149 patients were resuscitated from OHCA with sustained return of spontaneous circulation. After excluding patients who remained non-comatose following return of spontaneous circulation and those with incomplete scores, 1402 patients from EUCAR and 747 from GLOBAL-MIRACLE were included in the final analysis. The primary endpoint occurred in 54.4% of the study cohort. The performance of the Pre-MIRACLE₂ score for the primary endpoint was excellent, with an area under the receiver operating curve (AUROC) of 0.85 (95% CI 0.83, 0.87). From the prospective validation cohort (GLOBAL-MIRACLE), the AUROC was 0.85 (95% CI 0.82–0.88) with a calibration slope of 1.11 (95% CI 0.95–1.29). Conclusion: The Pre-MIRACLE₂ score has the potential to be an effective and pragmatic risk stratification tool for prediction of poor neurological outcome in patients with resuscitated OHCA of suspected cardiac aetiology in a pre-hospital environment or where pH cannot be measured.