Alright. [Karev is not about to talk him out of a smart decision made with a clear head.]
If the pain gets too much, tell me. This is not gonna be fun. [But he'll start getting to the meat of it, literally, where snipping off hanging skin is one thing - this is purposely tackling the rest with inadequate supplies. But it could be a lot worse. A finger is not a limb. The bleeders are small, he can staunch them as he goes. He almost apologizes as he works, but holds it in, knowing it'd only piss him off to have someone try to coddle him while he's holding himself together.
Instead:] You got anyone at home, anyone who should know where you are? [Focus on loved ones, Aidan. It might help.]