Oceanlover, welcome!
It's very important for you to be honest with the hospital about your drinking. You're not the first person that they have admitted that has a drinking problem. It's also important for them to know this for the anesthesiologist because your body may (important to note "may) react differently to the anesthesia. Everything is also confidential.
If you have withdrawals when you aren't drinking they can give you something to help with that. In fact, I believe that in the admitting workup the question will come up if you drink and how much. When they admitted my brother who has heart problems for fluid retention they asked the question. He drinks about every other night and if there's an 18 pack he'll find his way through it. He was honest and then they asked if he needed anything to help him but he said no.
Don't be embarrassed and be honest.
Come back here too and keep us posted!