This study will test whether a lower dose of epinephrine (0.5 mg) given during emergency treatment for out-of-hospital cardiac arrest helps more patients survive with good brain function, compared to the standard dose (1 mg). Adults who experience cardiac arrest outside the hospital and are treated by emergency medical teams will be randomly assigned to receive either the low dose or the standard dose of epinephrine. The study will compare survival and neurological outcomes between the two groups over 28 days.