Hey mate i've had surgery before when i wasn't wearing and i'm 180 percent sure i could have turned up with a piece and it would have made no difference. But in the past this guy called phoniex who claimed to be an anaesthetist said some hospitals have a policy of not letting people wear hair in to surgery theatres due to hygiene or something. That being said i'd doubt hair is going to kill you and i'd just take the risk if they want it off you can take it off easy.