I had a friend who was wrestling and play fighting with his cousin. He fell into a sliding glass door. The glass shattered and he cut his arm really bad all the way around it. Around his bicep and triceps. He said blood was just gushing out. He said as he laid there bleeding out everything started to go dark and he said it sounded like people were talking in slow motion. A nurse who happened to live in his apartment complex happened to see what happened and ran in and wrapped a towel around his arm and pulled it tight. He said he could see and hear everything normal after that.
I know that when I had a c-section I almost died because of blood loss. I had to get several blood transfusions. I know what happened to me was I could feel that I was very weak, then I threw up, then things started getting very blurry and the last thing I remember was a few people feeling of my arms and neck searching for a vein to give me some blood. But I didn't see them doing it. It's like I couldn't see right then but I could feel it. After that I don't remember anything else until I woke up in the recovery room. It was very scary. The doctor said that I almost died. So that's what I experienced with my blood loss situation.