My surgery is Wednesday too!! Congrats! and Happy Losing!
I suggest the nectar brand. I buy it at The Vitamin Shoppe (dont' know if that's available in your area) or online, but they are great. Doesn't even taste like Protein powder, mixes super easily, and they have tons of flavors including unflavored. 100 calories, 0 carbs, 0 sugar, 0 fat, and 23 gms carbs per scoop.
Hope I have helped.
Lyn