Hehe - I know how you're feeling.
I had my gall bladder removed recently. I had to wait a MONTH before they could schedule me for surgery and the earliest they could get me in was the week my period was to start.
I considered rescheduling the surgery because I couldn't stand the thought of having to deal with surgery AND my period...Ewww! Plus, I thought it'd be gross for the surgical team!!! But the surgeon's NP told me it was no big deal...they dealt with that all the time and it wasn't a problem for THEM. They use big table pads during all surgeries (colonoscopies, too) in case of any "leakage" of body fluids. They're kind of like those pads used to house-train puppies!
So since I also couldn't stand the thought of putting the surgery off any longer, I went with it. My period started the night before surgery.
I was really excited when they told me I could keep my undies & pad on during the surgery since it wouldn't be in the way. But while they were wheeling me to the OR I really had to pee and I told them that. So they decided to hook me up to a catheter. So after they put me under they stripped off my undies and put in the catheter...after surgery my undies were in a "HAZZARDOUS MATERIALS" bag in my private room! HA!