ABSTRACT

It has not been determined yet whether the number of defibrillation shocks delivered over the first 30 min of cardiopulmonary resuscitation (CPR) impacts the rate of successful return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest (OHCA).

We conducted a retrospective observational study in non-traumatic OHCA. Patients who were administered defibrillation shocks using a public automated external defibrillator (AED) were consecutively enrolled in the study. We assessed the relationship between ROSC and the number of prehospital defibrillation shocks and constructed an receiver operating characteristic (ROC) curve to illustrate the ability of repeated defibrillation shocks to predict ROSC over the first 30 min of CPR.

Increasing the number of defibrillation shocks progressively decreased the probability to achieve ROSC. The highest rate of ROSC (33%) was observed when four shocks were delivered. The ROC curve illustrated that the fourth shock maximised sensitivity and specificity (area under the curve [AUC]=0.72). The positive and negative predictive values for ROSC reached 82% and 48%, respectively, when <4 shocks were delivered.

The delivery of four defibrillation shocks in OHCA most related to ROSC. The evaluation of the number of delivered shock during the first 30 min of CPR is a simple tool that can be used for an early decision in OHCA patient.

Keywords: Number of defibrillation shocks, shockable rhythm, out-of-hospital cardiac arrest, resuscitation, outcome