Yeah there's a huge difference between dead bodies and anesthetized patients than real people in real pain. I've seen some messed up stuff in my job and I'm completely desinsitized to dead bodies. I once found a decapitated body and had to go searching for it's head which was no big deal. I've pulled bodies from burning buildings and their skin has all fallen off in my hands. But seeing live people in pain is horrible. Car crashes are the worst. People area always screaming and crying.
I recently went to a car crash where the driver was in a bad way - he was making some horrible nosies and once we got him out of the car the Dr's started to operate on him in the middle of the road to drain the blood that was pooling in his chest (he was semi-concious). I had to hold his legs still whilst the Dr's inserted IV's into the top of his legs by his dick...then his parents turned up on scene and saw him there. Their screams were unreal. He had two massive cardiac arrests whilst he was being treated in the road and although he got to hospital alive he died shortly after. I didn't sleep much that night.