Abstract 126: ’Tick Tock’ it’s Time to Shock; Increased Shock Latency is Associated With Intra-Arrest Transport and Reduced Survival From Out-Of-Hospital Cardiac Arrest

Introduction: Timely defibrillation of shockable rhythms during out of hospital cardiac arrest (OHCA) is an important link in the chain of survival. In 2011 the Salt Lake City Fire Department (SLCFD) adopted ECG filtering technology to allow rhythm interpretation during CPR and a protocol to defibrillate shockable rhythms immediately upon identification. Hypothesis: We hypothesized that, under the new protocol, time from observing VF to defibrillation would, on average, be less than the 2 minutes expected by guidelines. We also hypothesized that increased shock latency would be associated with intra-arrest transport and decreased survival. Methods: Prospectively collected and abstracted defibrillator data from non-traumatic cardiac arrest cases treated by ALS providers from SLCFD between Dec 2011 and June 2019 were analyzed along with Utstein variables and outcomes. Using the defibrillator manufacturer’s review software, the timing of observed rhythm changes and defibrillation events was manually abstracted based on post-incident physician interpretation. Generalized linear and Poisson mixed models were used for analysis. Results: A total of 696 cardiac arrests with 965 shocks delivered to shockable rhythms were analyzed after excluding pediatric cases, non-ALS cases, and cases in which the defibrillator file was lost or corrupted. Median time to defibrillation was 67 sec (IQR 30-143 sec) with mixed-effects grand mean of 106 sec (95% CI 96-117 sec). Delayed defibrillation (> 2 min) occurred in 293/965 (30%) of shocks. Transport of patients in arrest was associated with an increase in shock latency of 42 sec (95% CI 21-63 sec) compared to patients treated on scene. Among patients with an initial shockable rhythm, time from VF appearance to defibrillation was, on average, 40 sec (95% CI 15-66 sec) shorter among survivors than non-survivors. Conclusions: Use of an aggressive defibrillation protocol enabled by ECG filtering software resulted in a median time to defibrillation of under 2 minutes. Increasing shock latency was associated with intra-arrest transport providing a causal hypothesis for the poor outcomes observed in this population. We observed a negative association between survival and average time to defibrillation of shockable rhythms.