AED Use in Out-of-Hospital Cardiac Arrest: A New Algorithm Named "One Shock Per Minute"

Early use of semi-automated external defibrillators (AED) by Emergency Care teams in out-of-hospital cardiac arrest (OHCA), has been correlated with a significant gain in sequelae-free survival. The AED is programmed with an algorithm based recommended guidelines.

We will test a new algorithm that takes into account recent findings in pathophysiology.

Patients presenting with cardiovascular and pulmonary arrest treated by the BSPP Emergency Care who meet inclusion criterion are proposed for inclusion in the trial.

The aim of the trial is to evaluate a new AED algorithm that proposes a new timeline between the time devoted to administer a defibrillation shock, and the time devoted to chest compressions.

The new algorithm is entitled "one shock per minute". Use of this algorithm should validate several hypotheses:

• the importance of administering cardiac massage and artificial ventilation (CPR) prior to initiation of electrical shock treatment.
• the importance of continuing CPR immediately following electrical shock treatment
• the importance of reducing time between CPR procedures to a minimum
• the fact that three successive electrical shocks are of no therapeutic benefit.

We want to compare the control algorithm with the new one titled "one shock per minute", for shocked patients.

The sample size of this trial was calculated to provide a power of 85% and a type 1 error rate of alpha = 0.0294 for detecting an 11% increase in the rate of hospital admission, from its historical rate of 34% to a new rate of 45%. One interim analysis was planned with the stopping boundary alpha = 0.0294. This required inclusion of 430 patients in each group.

The primary endpoint is defined as "the admission of the patient alive at the hospital".

The secondary endpoints are defined as following :

• Detection of Palpable Carotid Pulse (ROSC) within the first 8 minutes after the connection of the AED The other secondary endpoint is survival to one year.

Concerning patients that do not receive shocks

They represent a priori 82% of the patients. The absolute number is a priori 3940, that is to say, 1970 in both two groups.

They will be used for an advanced observational descriptive study, to establish hypothesis for future studies.The same primary and secondary endpoints will be evaluated for them.

Among these patients not shocked, the algorithm foresees 60 seconds of CPR for the Control Group, and 90 seconds for the Trial Group. This setting relies on the hypothesis that increasing the time dedicated to chest compressions will increase the probability of return of a palpable pulse (ROSC), even for patients who do not fibrillate.

Statistical analysis will be completed by "Hôpital d'Instruction des Armées BEGIN - Epidemiology department"

We propose a comparison using the Chi square test for qualitative variables, Student's t test for quantitative variables, completion of a logistics model to analyze prognostic factors, as well as the proportional hazards model for survival analysis. Tests will be bilateral (significant p = 0,029 if we consider one intermediate analysis).

Overall analysis strategy will be defined and completed by the Epidemiology department of Hôpital d'Instruction des Armées BEGIN

Inclusion criteria

• Patients in a state of apparent death as noted on arrival of the emergency care team vehicle
• Resuscitation by first aid team with a minimum of three people
• Analysis of cardiac rhythm by the AED possible
• At least one appropriate shock delivered by the AED

Exclusion criteria

• Many victims (>3) that must be treated simultaneously
• Signs of certain death (lividity)
• Patient with palpable pulse on arrival of emergency care team
• Patient already connected to another device
• Incident involving an AED that requires a "materiovigilance" report