I've passed out numerous times from the cramping, sweats and pain while having D. In college, I cut my chin and needed stiches from passing out and hitting something. And I passed out twice in my high school years in public places. It was soooo awful. After I had a total hysterectomy six years ago (I had endometriosis around the bowel), I've only passed out once while in the middle of the cramps/sweats/pain. My family knows to just bring me a cold rag for the back of my neck, some ice water to drink, a pillow, and then leave me alone - since I usually end up having to take all my clothes off because I'm drenched in sweat.
On the bright side, when the cramps ease up, you get that great carthasis feeling.