It... is so easy to kill someone with the tools doctors use to do even minimally invasive procedure. The Human body is one whole machine working hard to maintain homeostasis. Theres a reason for the arduous medical schooling and fellowship.

Lidocaine aifaik depresses heartrates at high doses presumably with some kind of intravenous/intramuscular delivery as well. I'm no doctor but they probably cant remove or render the lidocaine inert fast enough to administer drugs to get your heart to beat itself again. Human bodies heal themselves, Doctors can only try to intervene and give your body a chance. Once their heart stopped, their fate was sealed as the potential for another heartbeat hit 0 when the lidocaine stopped it.

Another notable cause of death in butt related cosmetic surgery is fat injection, a BBL. If you accidentally inject fat into an artery the person just kinda dies.