I had it happen yesterday while I was watching my goat have a C-section. It was the third surgery that I have watched in person (her other C-section and a cat spay), but the vet had me, my brother, and my mom helping him this time because he needed help lifting, she was a bit big for the table, and he only had one tech there. She kept on opening her eyes, screamed a few times, kicked, and they kept on turning the gas up; I really hope its not common for them to do that. I was fine watching her C-section last year with live kids (and without her obvious pain during the surgery), and for the first part of this one. However, after I found out that the kid was dead and he started stiching her up, I started feeling really hot, nauseous, and lightheaded. I ended up leaving for a few minutes and coming back, and then I felt a bit better. Needless to say, its the end of her career as a mother.
The vet still said I could shadow him when I can.