So, you were mistaken here as far as this being a 100% sure thing?
No, if you have no blood pressure you are not going to remain conscious; what I was saying there is that certain drugs will elevate your blood pressure so that under normal circumstances when your BP would have dropped from extreme pain or sudden blood loss the drugs will keep it up just enough to keep you going longer than average.
Drugs are not going to keep blood pumping when there is no blood to pump, or the heart is so damaged it no longer receives impulses to beat, or the brain stops sending messages to pump. That is just fact. Well I guess we could get pedantic and discuss heart lung machines etc... but we aren't.
And I never said 100% for anything. I am a scientist and not that stupid.