The human body has 8 – 10 pints of blood in their body, depending on build. It takes the loss of two to three pints of blood to go into shock, and a loss of four to six pints of blood to cause death (again, depending on the person’s build, age, and health.) During bleed-out, the person will feel dizzy, weak, and generally lapse into shock.
Interestingly, exsanguination (loss of blood) is the most common cause of death on the battlefield.
Now, on the matter of self-amputation…
Here’s an excerpt from an interview with Aron Ralston, the climber whose story is the basis for the film 127 Hours.
But how did someone who had been repulsed by dissecting a sheep’s eyeball in ninth grade manage to sever his own hand?
It was strange. I kind of entered a flow state. I’ve been there before while climbing. You are not thinking ahead. You are just thinking about what is in front of you each second.
I was so engrossed that I had to catch myself when I got to the arteries so that I didn’t sever those without a tourniquet on.
The answer seems obvious, but did it hurt?
Well, I didn’t have any sensation in my right hand from the time of the accident onward. However, I did feel pain coming from the area where the boulder rested on my wrist.
When I amputated, I felt every bit of it. It hurt to break the bone, and it certainly hurt to cut the nerve. But cutting the muscle was not as bad.
Overall, it was a hundred times worse than any pain I’ve felt before. It recalibrated what I’d understood pain to be. At the same time, it was also the most beautiful thing I’ve ever felt.
Ralston talks in this video (below) about the logistics of self-amputation. Warning for the squeamish: his description is pretty graphic. Of particular interest is the bit about needing to crack the bones in order to get the job done. It strikes me that though the arm bones are thicker and stronger than the wrist bones, Kev’s description in the play of the difficulty of cutting off his hand is spot-on.
Here’s some wrist anatomy…