If I gave a drug to a patient who holds a valid Ministry DNR that resulted in either apnea or respiratory depression, can I bag that patient since I essentially caused the respiratory problem?

Should I ask for a DNR in every scenario where I may use what’s contraindicated? If I were to show up for an unconscious but not VSA female and her husband is on scene and doesn’t mention the DNR, should I assume they want treatment and continue with inserting an OPA and bagging if necessary or should I ask for a DNR before starting treatment? Would I get in trouble in this scenario if I treated this patient without the husband saying anything and then once we got to the hospital found out they had a DNR?

I was just reviewing a 2012 webinar regarding DNR confirmation forms. It was said that a DNR confirmation form is a contraindication for transcutaneous pacing but not for synchronized cardioversion. Is this the case? And if so then why? Also, what about the administration of other ALS drugs such as Atropine, Dopamine, and Adenosine?