Abstract 235: The Association Between No-Flow Interval and Neurological Outcomes in Out-Of-Hospital Cardiac Arrest: Implications for Rescuer Response, Initiating Resuscitation, and ECPR Candidacy Evaluation

Introduction: The benefits of early CPR are evident, however the relationship between the no-flow interval and neurological outcomes may assist clinicians with resuscitation management. Methods: We examined emergency medical system-treated non-traumatic out-of-hospital cardiac arrests from two clinical trials (PRIMED and CCC; 2006-2015), including only bystander witnessed cases without bystander resuscitation. We created a subgroup to simulate ECPR-treated cases (witnessed, age ≤65, non-asystole initial rhythm, and ROSC >30 minutes). We fit an adjusted logistic regression model to estimate the relationship between the “no-flow” interval (911 call-to-initiation of CPR) and favorable neurological outcome (MRS ≤3) at hospital discharge, and created a cubic spline curve. Results: Of 43,593 trial cases, 7299 were included; 616 (8.4%; 95% CI 7.8-9.1%) favourable neurological outcomes. The no-flow interval (per minute) was associated favorable neurological outcomes (adjusted OR 0.88, 95% CI 0.85-0.91). The adjusted probability of a favorable neurological outcome decreased by 0.52% (95% CI 0.39-0.65) per no-flow minute. No patients (0%; 1-sided 97.5% CI 0-0.051%) had both a no-flow duration >20 minutes and a favorable neurological outcome. In the ECPR group, 15 (9.9%; 95% CI 5.1-15%) had favourable neurological outcomes; 0/152 (0%; 1-sided 97.5% CI 0-2.4%) had both a no-flow interval >10 minutes and a favourable neurological outcome. Conclusions: The odds of a favorable neurological outcome decrease as the no-flow interval increases, highlighting the urgency of rescuer response. We found no favorable outcomes among cases with >20 minutes of no-flow duration, which may assist providers with decisions of starting or terminating resuscitation. Among ECPR-eligible cases with prolonged resuscitative efforts there were no favourable neurological outcomes among those with a no flow-interval >10 minutes, which may assist with ECPR candidacy assessment.