I Have An Endoscopy Scheduled For 7:30am Today, I Have

I have an endoscopy scheduled for 7:30am today, I have sever PTSD and am terrified of doctors , let alone being put under and having no idea what they could do to me while I lay unconscious and vulnerable on a table. Basically, I'm having a f*^@ing panic attack and NEED A CIGARETTE!!!!! Will that f up my. Results??? Bc I'm going on 34 hrs of no sleep and 5 hours without a cig. Sorry for the cursing I am just really freaking out, thank you.