Abstract 187: Preshock Pause Intervals and Rearrest After Resuscitation from Out-of-Hospital Cardiac Arrest

Abstract

Background: Loss of pulses after successful return of spontaneous circulation (ROSC) during resuscitation from out-of-hospital cardiac arrest (OHCA) is known as re-arrest (RA). Recent studies have provided estimates of the rate occurrence of re-arrest - as high as 38% -, but the causes and characteristics of RA are not yet fully understood. One plausible contributor to RA is the pre-shock pause (PSP) interval - the time interval between the last chest compression and a defibrillating shock - which has been shown to predict survival to hospital discharge. Objective: Measure the PSP time interval in cases of OHCA with and without RA in order to: a) provide an estimate of the PSP in cases with RA, and b) compare the PSP of cases with RA to cases without PSP. Methods: Case data for emergency medical services (EMS)-treated OHCA were obtained from the Pittsburgh site of the multi-center Resuscitation Outcomes Consortium (ROC) and were part of a previously identified dataset (n = 113) used to compare ECG characteristics of RA cases to those without RA. A subset of these cases was identified that received at least one shock during treatment by EMS. Time-coded impedance, compression force, compression depth, or audio recordings accompanying each ECG trace were used to calculate the PSP to the nearest second for each shock in each case. The PSP for shocks that followed ROSC without preceding compressions were calculated as the interval between loss of pulses and the shock. All other PSP were calculated as the difference between the time of the final pre-shock compression and shock delivery. The kruskal-wallis test was used to compare the medians of RA and no-RA PSP with an alpha level of 0.05. Results: Fifty-six cases were identified with at least 1 EMS-delivered defibrillating shock. Of these, 27 (48%) cases had at least one instance of RA. For a total of 159 shocks in both RA and no-RA groups, the median (IQR) PSP was 16s (12.75). The median (IQR) PSP for the RA group (n = 101) was 16s (14), while the median (IQR) PSP for the no-RA group (n = 58) was 14s (11). The median PSP of RA and no-RA groups were not significantly different (p = 0.15). Conclusion: The PSP for EMS-treated cases of OHCA with RA had a median duration of 16s. In this limited study, PSP were not different between groups with and without RA.