I don't think that it's an issue if you're taking T during surgery unless you have some other medical condition which could mean that the T would possibly affect things like bleeding.
Like chipper, my surgeon didn't even mention stopping T when I had top surgery. Some surgeons do, however.
But I don't really understand why a trans* guy would be asked to stop T when a cismale isn't castrated or asked to take T blockers when having the same surgery. *shrug*
