I've had to leave O.R. twice due "erm, I'm not okay" moments I've being pretty sure I'll faint or vomit or both - once during spinal surgery and one c-section (if only I'd lasted a few more moments in that one! I heard squalling almost the second I closed the door behind me!), I've made it through okay on a hysterectomy and another c-section. (psych nursing hasn't offered too many fainting moments) Most interested thing I didn't pass out during was a chest wound dressing wherein I could see the heart beating - really cool.