Hi,
My brother had his done under a general, as his doctor felt there was a
possibility of him having a panic attack during the procedure. Obviously
doctors would usually prefer to use a local because of cost / risks, but
there are occasions when they may feel a general is the better option for
one of a variety of reasons. I'm guessing that in your case they think that
there might be more discomfort than usual attached to the procedure and
would prefer a general for that reason.
HTH
David
www.vasectomy-information.com