I don't know if you can see the up side in what happened yesterday but knowing your Dad was not the emergency surgery and that he was stable enough to wait until today is a positive sign.
I know he is on IV therapy for hydration as well as some nutrition and I would even guess once they were sure he was not going to surgery yesterday they made have given him something lite to eat and drink.
I have been at the bedside of my Father, and both of my sisters as well as my husband through many surgeries and I found when I became upset and wanting to lash out at the staff that my loved one would ask me not to as they were already stressing and were afraid if I made waves the staff would become hard to deal with.
If you have a truly justified reason to make a formal complaint - send the mail to the right address or ask to talk to a Supervisor but do your best to remain assertive and not aggressive. I can switch from assertive to aggressive in the blink of an eye which truly causes me more stress as I cannot get my words to make any sense.
Praying for all of you and know we are here to support you.
and Heart/Cardiovascular Disease. "She Stood in the Storm & When the Wind Did Not Blow Her Away, She Adjusted Her Sails."