Is it normal to feel light headed when you hear about medical procedures?

Whenever I hear a clinical, detailed medical description of a medical procedure I get light headed and feel like I'm going to pass out. I understand that the person is going to be under heavy sedatives, and not feel a thing but the thought of what will happen to them is nauseating. I'm not afraid of doctors or dentists or anything like that, and I watch plenty of violent television. I've even watched shows like House which depict the medical procedures and it's all fine. The only time this happens is when I am having it described to me or if I am reading about it.