Abstract 49: Defibrillation Success is not Meaningfully Associated with Duration of the Pre-shock Pause in Chest Compressions
Background and Methods A recent study in a small patient cohort found that for shocks delivered during ACLS resuscitation, longer pre-shock pauses in chest compressions were associated with substantially lower ventricular fibrillation (VF) termination rates. We analyzed data from a large patient cohort to further evaluate the relationship between pre-shock chest compression pauses and shock outcomes. Data were gathered from VF cardiac arrest patients treated prehospital by ACLS responders using biphasic defibrillators (LIFEPAK 12, Medtronic). For each shock, electronic ECG and continuous transthoracic impedance data were used to determine VF termination (removal of VF for > 5 sec), return of a sustained organized rhythm (return of QRS complexes > 40 bpm within 60 sec), and duration of the pre-shock pause in chest compressions.
Results A total of 776 shocks in 263 patients were analyzed (Figure⇓). Logistic regression showed a very small but statistically significant increase in VF termination probability with increasing pre-shock pause duration (odds ratio [95% CI] 1.03 [1.01–1.05]). This effect disappeared when analysis was limited to pauses < 30 sec (p = 0.10). There was no significant relationship between pause duration and return of an organized rhythm (p = 0.07).
Conclusions Minimizing overall interruptions in chest compressions is an important goal for resuscitation. However, data from this large patient cohort indicate that there is no clinically significant association between the rate of VF termination, or the rate of return of a sustained organized rhythm, and the duration of the pause in chest compressions occurring immediately before shock delivery.