After I had my open heart surgery in 2002, I asked my doctor if he'd had to use blood transfusions. This was heart artery bypass surgery. You know what pulses through those veins.
His answer was that they had several pints of blood at the ready in case of emergency, but they did not actually need to transfuse me. I slept through the whole thing, but as he explained they slowed everything down while I was under the knife (no idea how they did that) and used a heart bypass machine to keep my brain alive. Most of the time during the operation was used for removing a vein in my leg (open up, snip-snip, cauterize the ends, sew me back up) and cracking my chest (blood loss was minimized by avoiding arteries and cauterizing veins). Once the heart was available, only small incisions were made to patch the new veins around the blockages. My case was complicated because they had to take a large chuck out of an artery feeding my left shoulder and arm in order to get a larger piece for a blockage in one of the feed arteries.
In spite of all of that, my doctor said I loss less than two pints of blood, an amount that the body can replace in just a few hours. So even though blood was available, none was used. I was no longer a JW, so I had no qualms at all about taking blood, but the doctor obviously felt that was not a necessity even in my rather complicated case.
I've had three other surgeries, two abdominal. I both cases the doctors did not need or even consider the use of blood.
I think doctors see blood as necessary only in cases of severe blood loss like gunshots, car accidents and decapitations. The important thing is that knowing that doctors do not automatically start giving blood transfusions everytime someone goes under the knife is good to know (as my doctor said, "That is the lazy way to do surgery..."). But when they do feel they need to use that option, it is definitely a life/death situation.
JV