I'm surprised your doctor doing the surgery has not sent you any guidelines. I would call their office and talk to the nurse. I had to go for many test such as upper GI, echo cardiogram, complete physical with my family doc, EKG, pulmonary test, blood test a few weeks before surgery and at hospital, etc, etc.
My pre op instructions were several things, to summarize some key points:
1. 1 week before no aspirin/advil, No estrogen products
2. 2 days before full liquids. 40 g of Protein drinks (my doctor wanted me to lose weight prior to surgery so he wanted me to be on full liquids two weeks before (easier said than done).
3. Nothing including Water by midnight before surgery
4. If you're on any medications such as blood pressure, check with your doctor about taking them
I honestly don't know if all doctors have same instructions but you should make sure.