FWIW,
About a year ago, in the middle of the night, I woke up to my wife being ill in the bathroom, next room, I didn't panic, I lied there for a moment or two, then realised things were serious.
I got up and started getting dressed before she even called me.
My next action was to pick the phone up and dial 999.
Now I am full 3 day FAW trained, as was my wife, but hers has expired.
We looked at each other and we both thought the same thing.
I dialed 999, and went through the symptoms with the call responder.
The next thing I was told asked was did we have asprin and could I administer it, no question that I can recall, about allergy.
We both knew what they suspected, the same as we did, her brother died at 39 of a heart attack, her mother at 52 of a heart attack.
The call centre and paramedics were great.
As it turned out, it was not heart related! Phew!!!
However, given that experience, I would have no qualms if I thought that the patient was suffering an arrest I would check with the call centre and if they said administer I would, and if the casualty could confirm that as far as they knew they were not allergic I would administer and be damned.
I would rely on the "good samaritan" philosopy, at least I would try to save the life.
In the same way, I WOULD apply a torniquet to a limb, even against guidance if someone was likely IMHO to bleed out from a wound and the flow could not be stemmed, and again be damned.
I would rather keep someone alive with an amputation, than watch them die.
Controversial probably, have I had to do it, no, do I want to have to do it no.
However, sometimes, one has to act on what is in front of you, the data that you have and process it on the spot, and make snap decisions based on that, you do what you can do, and the best you can.
Some people don't have the confidence of their convictions, being an Engineer, then I am paid for my opinions, and I have to live with my decisions, especially running my own company, so I am willing to accept the ramifications of my actions.