Strong "Fight or Flight" response with Endoscopy?

Maybe you had a paradoxical reaction to one of the medications. Paradoxical reactions are when the opposite of the expected effect of the medication is what happens to the patient. Although rare, they can happen. The drugs you were given were supposed to sedate you; maybe one of them you had the opposite reaction to, and that kept you from going to sleep normally. Perhaps that's why the other times you were sedated went OK; maybe they used a different combination of drugs. In any case, if you're concerned, talk to the doctor who will be doing it about the past endoscopy. They'll probably gladly work with you to make a plan to keep it from happening during their procedure.