system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why do we not bleed out during a surgery?

Myself, having gone through a surgery, I wonder why we do not lose huge quantities of blood during a surgery.
gpt
That is one of the things about learning to be a surgeon that makes it more difficult than butchery. Anesthesia can be used to lower blood pressure, medicines applied to reduce bleeding, and as the surgeon cuts they will try to avoid major blood vessels and clamp shut those they must cut. Smaller ones may even be cauterized, burned closed by a heated tool.

Most of the time (~94%) blood transfusions are not given during surgery because they are not necessary. Keeping your own blood inside you while making holes for them to work is part of why they need so much training.