If, as the OP suggests, we are at the hospital already, I'd be inclined to initiate CPR and ventilate the pt. while we wheeled them in. Taking the time to apply defibrillator pads would be detrimental to the pt. because, as we all know, time is tissue. The sooner we can get them to definitive care, the better the chance of a positive outcome. Why mess about in the ambulance?