The objective of this randomized controlled trial is to evaluate the effectiveness of a low cumulative dose of epinephrine compared to a standard cumulative dose of epinephrine during resuscitation from ventricular fibrillation (VF) or ventricular tachycardia (VT) in adult out-of-hospital cardiac arrest (OHCA) patients.

This study is designed as a prospective, multicentre, single-blinded randomized controlled trial (RCT) where eligible OHCA patients are randomized to receive a low cumulative dose of epinephrine (low dose epinephrine, up to 2mg total) or a standard cumulative dose of epinephrine (standard dose epinephrine, up to 6mg total) in a 1:1 fashion.

Eligible OHCA patients will be treated by paramedics who will initiate cardiopulmonary resuscitation (CPR) and the delivery of defibrillation shocks per paramedic agencies' treatment protocols. After one defibrillation and when feasible, paramedics will establish peripheral intravenous (IV) access, and patients will be randomly allocated to either the low dose or standard dose treatment arm. Epinephrine doses (according to treatment assignment) will be administered every 3-5 minutes, based on current guidelines and paramedic protocols, until the first return of spontaneous circulation (ROSC) is achieved or if resuscitation has been terminated by the base hospital physician. Other medications (e.g. antiarrhythmics, magnesium, beta blockers) and interventions (e.g. intubation) may be interposed as required. Follow-up will take place using a combination of administrative databases (e.g. the Discharge Abstract Database and the National Ambulatory Care Reporting System) and telephone interviews.

This RCT will evaluate a fundamental change in the treatment of OHCA. The investigators hypothesize that a low cumulative dose of epinephrine will improve patient survival to hospital discharge compared to a standard cumulative dose of epinephrine. Please feel free to contact epidose@unityhealth.to for further information.

Inclusion Criteria:

• Out-of-hospital cardiac arrest treated by paramedics
• Initial recorded cardiac rhythm of VF or pulseless VT, or, AED shock on first analysis administered or witnessed by EMS (paramedic or fire)
• Established intravenous vascular access

Exclusion Criteria:

• Known or apparent age <18 years
• Initial recorded cardiac rhythm of VF or pulseless VT, or, AED shock on first analysis administered or confirmed by paramedics
• Cardiac arrest due to an obvious non-cardiac primary cause (e.g. blunt or penetrating trauma, exsanguination, burns, drug overdose, drowning, anaphylaxis, sudden asphyxiation, etc.)
• Administration of intramuscular, endotracheal tube, or intraosseous epinephrine
• Prisoners or persons in police custody
• Known allergy or sensitivity to epinephrine