very quickly: By time you know you are hurt, it is over. With the larger organs, the victim probably faints, or goes into shock. Or they give you a bullet on which to bite, whiskey, drugs, people hold down the victim, and death, the heart just stops beating, stroke, the brain just quits etc.
Most of the time they probably just use anesthesia, or a 2by4 up side the head. With what kind of people do you think you are dealing, anyway, human-kind?! Think of Hillray at the operating table, removing one, little ovary. I can see her using her teeth and finger-nails